Merge pull request #676 from schungx/master

Code refactor.

CHANGELOG.md

@@ -4,14 +4,37 @@ Rhai Release Notes
 Version 1.12.0
 ==============
 
-Buf fixes
+Bug fixes
 ---------
 
 * Integer numbers that are too large to deserialize into `INT` now fall back to `Decimal` or `FLOAT` instead of silently truncating.
+* Parsing deeply-nested closures (e.g. `||{||{||{||{||{||{||{...}}}}}}}`) no longer panics but will be confined to the nesting limit.
+
+Breaking API changes
+--------------------
+
+* The callback for initializing a debugger instance has changed to `Fn(&Engine, Debugger) -> Debugger`. This allows more control over the initial setup of the debugger.
+* The internal macro `reify!` is no longer available publicly.
+
+Deprecated API's
+----------------
+
+* `Module::with_capacity` is deprecated.
+* The internal method `Engine::eval_statements_raw` is deprecated.
+
+Speed improvements
+------------------
+
+* The functions registration mechanism is revamped to take advantage of constant generics, among others.
+* This yields a 10-20% speed improvements on certain real-life, function-call-heavy workloads.
 
 Net features
 ------------
 
+### `!in`
+
+* A new operator `!in` is added which maps to `!(... in ...)`.
+
 ### `Engine::call_fn_with_options`
 
 * `Engine::call_fn_raw` is deprecated in favor of `Engine::call_fn_with_options` which allows setting options for the function call.
@@ -21,11 +44,15 @@ Net features
 Enhancements
 ------------
 
+* Optimizations have been done to key data structures to minimize size and creation time, which involves turning rarely-used fields into `Option<Box<T>>`. This resulted in some speed improvements.
 * `CallableFunction` is exported under `internals`.
 * The `TypeBuilder` type and `CustomType` trait are no longer marked as volatile.
 * `FuncArgs` is also implemented for arrays.
 * `Engine::set_XXX` API can now be chained.
 * `EvalContext::scope_mut` now returns `&mut Scope` instead of `&mut &mut Scope`.
+* Line-style doc-comments are now merged into a single string to avoid creating many strings. Block-style doc-comments continue to be independent strings.
+* Block-style doc-comments are now "un-indented" for better formatting.
+* Doc-comments on plugin modules are now captured in the module's `doc` field.
 
 
 Version 1.11.0

Cargo.toml

@@ -23,7 +23,7 @@ ahash = { version = "0.8.2", default-features = false, features = ["compile-time
 num-traits = { version = "0.2", default-features = false }
 bitflags = { version = "1", default-features = false }
 smartstring = { version = "1", default-features = false }
-rhai_codegen = { version = "1.4.1", path = "codegen", default-features = false }
+rhai_codegen = { version = "1.5.0", path = "codegen", default-features = false }
 
 no-std-compat = { version = "0.4", default-features = false, features = ["alloc"], optional = true }
 libm = { version = "0.2", default-features = false, optional = true }
@@ -43,7 +43,7 @@ serde_json = { version = "1.0", default-features = false, features = ["alloc"] }
 [features]
 default = ["std", "ahash/runtime-rng"]  # ahash/runtime-rng trumps ahash/compile-time-rng
 std = ["ahash/std", "num-traits/std", "smartstring/std"]
-unchecked = []                  # unchecked arithmetic
+unchecked = []                  # disable safety checks
 sync = []                       # restrict to only types that implement Send + Sync
 no_position = []                # do not track position in the parser
 no_optimize = []                # no script optimizer

README.md

@@ -33,7 +33,7 @@ Standard features
 -----------------
 
 * Simple language similar to JavaScript+Rust with [dynamic](https://rhai.rs/book/language/dynamic.html) typing.
-* Fairly efficient evaluation (1 million iterations in 0.23 sec on a single-core, 2.3 GHz Linux VM).
+* Fairly efficient evaluation (1 million iterations in 0.14 sec on a single-core 2.6 GHz Linux VM).
 * Tight integration with native Rust [functions](https://rhai.rs/book/rust/functions.html) and [types](https://rhai.rs/book/rust/custom-types.html), including [getters/setters](https://rhai.rs/book/rust/getters-setters.html), [methods](https://rhai.rs/book/rust/methods.html) and [indexers](https://rhai.rs/book/rust/indexers.html).
 * Freely pass Rust values into a script as [variables](https://rhai.rs/book/language/variables.html)/[constants](https://rhai.rs/book/language/constants.html) via an external [`Scope`](https://rhai.rs/book/engine/scope.html) - all clonable Rust types are supported; no need to implement any special trait. Or tap directly into the [variable resolution process](https://rhai.rs/book/engine/var.html).
 * Built-in support for most common [data types](https://rhai.rs/book/language/values-and-types.html) including booleans, [integers](https://rhai.rs/book/language/numbers.html), [floating-point numbers](https://rhai.rs/book/language/numbers.html) (including [`Decimal`](https://crates.io/crates/rust_decimal)), [strings](https://rhai.rs/book/language/strings-chars.html), [Unicode characters](https://rhai.rs/book/language/strings-chars.html), [arrays](https://rhai.rs/book/language/arrays.html) (including packed [byte arrays](https://rhai.rs/book/language/blobs.html)) and [object maps](https://rhai.rs/book/language/object-maps.html).

codegen/Cargo.toml

@@ -1,11 +1,11 @@
 [package]
 name = "rhai_codegen"
-version = "1.4.3"
+version = "1.5.0"
 edition = "2018"
 resolver = "2"
 authors = ["jhwgh1968", "Stephen Chung"]
 description = "Procedural macros support package for Rhai, a scripting language and engine for Rust"
-keywords = ["rhai", "scripting", "scripting-engine", "scripting-language", "embedded", "plugin", "macros", "code-generation"]
+keywords = ["scripting", "scripting-engine", "scripting-language", "embedded", "plugin"]
 categories = ["no-std", "embedded", "wasm", "parser-implementations"]
 homepage = "https://rhai.rs/book/plugins/index.html"
 repository = "https://github.com/rhaiscript/rhai"
@@ -24,5 +24,5 @@ syn = { version = "1.0", features = ["full", "parsing", "printing", "proc-macro"
 quote = "1"
 
 [dev-dependencies]
-rhai = { path = "..", version = "1.11", features = ["metadata"] }
+rhai = { path = "..", version = "1.12", features = ["metadata"] }
 trybuild = "1"

codegen/src/attrs.rs

@@ -145,6 +145,7 @@ pub fn inner_item_attributes<T: ExportedParams>(
 pub fn doc_attributes(attrs: &[syn::Attribute]) -> syn::Result<Vec<String>> {
     // Find the #[doc] attribute which will turn be read for function documentation.
     let mut comments = Vec::new();
+    let mut buf = String::new();
 
     for attr in attrs {
         if let Some(i) = attr.path.get_ident() {
@@ -158,17 +159,28 @@ pub fn doc_attributes(attrs: &[syn::Attribute]) -> syn::Result<Vec<String>> {
 
                     if line.contains('\n') {
                         // Must be a block comment `/** ... */`
+                        if !buf.is_empty() {
+                            comments.push(buf.clone());
+                            buf.clear();
+                        }
                         line.insert_str(0, "/**");
                         line.push_str("*/");
+                        comments.push(line);
                     } else {
                         // Single line - assume it is `///`
-                        line.insert_str(0, "///");
+                        if !buf.is_empty() {
+                            buf.push('\n');
+                        }
+                        buf.push_str("///");
+                        buf.push_str(&line);
+                    }
+                }
+            }
+        }
     }
 
-                    comments.push(line);
-                }
-            }
-        }
+    if !buf.is_empty() {
+        comments.push(buf);
     }
 
     Ok(comments)

codegen/src/function.rs

@@ -674,6 +674,7 @@ impl ExportedFn {
         let arg_count = self.arg_count();
         let is_method_call = self.mutable_receiver();
         let is_pure = !self.mutable_receiver() || self.params().pure.is_some();
+        let pass_context = self.pass_context;
 
         let mut unpack_statements = Vec::new();
         let mut unpack_exprs = Vec::new();
@@ -689,7 +690,7 @@ impl ExportedFn {
         let skip_first_arg;
 
         if self.pass_context {
-            unpack_exprs.push(syn::parse2::<syn::Expr>(quote! { context }).unwrap());
+            unpack_exprs.push(syn::parse2::<syn::Expr>(quote! { context.unwrap() }).unwrap());
         }
 
         // Handle the first argument separately if the function has a "method like" receiver
@@ -860,13 +861,14 @@ impl ExportedFn {
             #(#cfg_attrs)*
             impl PluginFunction for #type_name {
                 #[inline(always)]
-                fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                     #(#unpack_statements)*
                     #return_expr
                 }
 
                 #[inline(always)] fn is_method_call(&self) -> bool { #is_method_call }
                 #[inline(always)] fn is_pure(&self) -> bool { #is_pure }
+                #[inline(always)] fn has_context(&self) -> bool { #pass_context }
             }
         }
     }

codegen/src/module.rs

@@ -106,6 +106,7 @@ impl Module {
 impl Parse for Module {
     fn parse(input: ParseStream) -> syn::Result<Self> {
         let mut mod_all: syn::ItemMod = input.parse()?;
+
         let fns: Vec<_>;
         let mut consts = Vec::new();
         let mut custom_types = Vec::new();
@@ -269,11 +270,17 @@ impl Module {
         let (.., orig_content) = mod_all.content.take().unwrap();
         let mod_attrs = mem::take(&mut mod_all.attrs);
 
+        #[cfg(feature = "metadata")]
+        let mod_doc = crate::attrs::doc_attributes(&mod_attrs)?.join("\n");
+        #[cfg(not(feature = "metadata"))]
+        let mod_doc = String::new();
+
         if !params.skip {
             // Generate new module items.
             //
             // This is done before inner module recursive generation, because that is destructive.
             let mod_gen = crate::rhai_module::generate_body(
+                &mod_doc,
                 &mut fns,
                 &consts,
                 &custom_types,

codegen/src/rhai_module.rs

@@ -26,6 +26,7 @@ pub struct ExportedType {
 }
 
 pub fn generate_body(
+    doc: &str,
     fns: &mut [ExportedFn],
     consts: &[ExportedConst],
     custom_types: &[ExportedType],
@@ -230,7 +231,7 @@ pub fn generate_body(
                 syn::parse2::<syn::Stmt>(quote! {
                     #(#cfg_attrs)*
                     m.set_fn_with_comments(#fn_literal, FnNamespace::#ns_str, FnAccess::Public,
-                             #param_names, &[#(#fn_input_types),*], &[#(#comments),*], #fn_token_name().into());
+                             #param_names, [#(#fn_input_types),*], [#(#comments),*], #fn_token_name().into());
                 })
                 .unwrap()
             });
@@ -246,6 +247,17 @@ pub fn generate_body(
         gen_fn_tokens.push(function.generate_impl(&fn_token_name.to_string()));
     }
 
+    let module_docs = if doc.is_empty() {
+        None
+    } else {
+        Some(
+            syn::parse2::<syn::Stmt>(quote! {
+                m.set_doc(#doc);
+            })
+            .unwrap(),
+        )
+    };
+
     let mut generate_fn_call = syn::parse2::<syn::ItemMod>(quote! {
         pub mod generate_info {
             #[allow(unused_imports)]
@@ -254,6 +266,7 @@ pub fn generate_body(
             #[doc(hidden)]
             pub fn rhai_module_generate() -> Module {
                 let mut m = Module::new();
+                #module_docs
                 rhai_generate_into_module(&mut m, false);
                 m.build_index();
                 m

codegen/src/test/function.rs

@@ -280,12 +280,13 @@ mod generate_tests {
                     #[inline(always)] pub fn param_types() -> [TypeId; 0usize] { [] }
                 }
                 impl PluginFunction for Token {
-                    #[inline(always)] fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    #[inline(always)] fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         Ok(Dynamic::from(do_nothing()))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -318,13 +319,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<usize>();
                         Ok(Dynamic::from(do_something(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -357,13 +359,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<usize>();
-                        Ok(Dynamic::from(do_something(context, arg0)))
+                        Ok(Dynamic::from(do_something(context.unwrap(), arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { true }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -399,12 +402,13 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         Ok(Dynamic::from(return_dynamic()))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -432,13 +436,14 @@ mod generate_tests {
             }
             impl PluginFunction for TestStruct {
                 #[inline(always)]
-                fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                     let arg0 = mem::take(args[0usize]).cast::<usize>();
                     Ok(Dynamic::from(do_something(arg0)))
                 }
 
                 #[inline(always)] fn is_method_call(&self) -> bool { false }
                 #[inline(always)] fn is_pure(&self) -> bool { true }
+                #[inline(always)] fn has_context(&self) -> bool { false }
             }
         };
 
@@ -465,7 +470,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<usize>();
                         let arg1 = mem::take(args[1usize]).cast::<usize>();
                         Ok(Dynamic::from(add_together(arg0, arg1)))
@@ -473,6 +478,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -505,7 +511,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<usize>();
                         let arg0 = &mut args[0usize].write_lock::<usize>().unwrap();
                         Ok(Dynamic::from(increment(arg0, arg1)))
@@ -513,6 +519,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]
@@ -546,13 +553,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for Token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).into_immutable_string().unwrap();
                         Ok(Dynamic::from(special_print(&arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
                 #[allow(unused)]
                 #[doc(hidden)]

codegen/src/test/module.rs

@@ -92,10 +92,11 @@ mod module_tests {
                 .cloned()
                 .collect::<Vec<_>>(),
             vec![
-                "/// This is a doc-comment.",
-                "/// Another line.",
-                "/// block doc-comment ",
-                "/// Final line.",
+                "\
+                /// This is a doc-comment.\n\
+                /// Another line.\n\
+                /// block doc-comment \n\
+                /// Final line.",
                 "/** doc-comment\n                    in multiple lines\n                 */"
             ]
         );
@@ -385,12 +386,13 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_mystic_number_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         Ok(Dynamic::from(get_mystic_number()))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -402,6 +404,12 @@ mod generate_tests {
     #[test]
     fn one_factory_fn_with_comments_module() {
         let input_tokens: TokenStream = quote! {
+            /// This is the one_fn module!
+            /** block doc-comment
+             *  multi-line
+             */
+            /// Another line!
+            /// Final line!
             pub mod one_fn {
                 /// This is a doc-comment.
                 /// Another line.
@@ -418,6 +426,12 @@ mod generate_tests {
         };
 
         let expected_tokens = quote! {
+            /// This is the one_fn module!
+            /** block doc-comment
+             *  multi-line
+             */
+            /// Another line!
+            /// Final line!
             pub mod one_fn {
                 /// This is a doc-comment.
                 /// Another line.
@@ -436,6 +450,7 @@ mod generate_tests {
                 #[doc(hidden)]
                 pub fn rhai_module_generate() -> Module {
                     let mut m = Module::new();
+                    m.set_doc("/// This is the one_fn module!\n/** block doc-comment\n             *  multi-line\n             */\n/// Another line!\n/// Final line!");
                     rhai_generate_into_module(&mut m, false);
                     m.build_index();
                     m
@@ -444,11 +459,8 @@ mod generate_tests {
                 #[doc(hidden)]
                 pub fn rhai_generate_into_module(m: &mut Module, flatten: bool) {
                     m.set_fn_with_comments("get_mystic_number", FnNamespace::Internal, FnAccess::Public,
-                             Some(get_mystic_number_token::PARAM_NAMES), &[], &[
-                                 "/// This is a doc-comment.",
-                                 "/// Another line.",
-                                 "/// block doc-comment ",
-                                 "/// Final line.",
+                             Some(get_mystic_number_token::PARAM_NAMES), [], [
+                                 "/// This is a doc-comment.\n/// Another line.\n/// block doc-comment \n/// Final line.",
                                  "/** doc-comment\n                    in multiple lines\n                 */"
                              ], get_mystic_number_token().into());
                     if flatten {} else {}
@@ -463,12 +475,13 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_mystic_number_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         Ok(Dynamic::from(get_mystic_number()))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -521,13 +534,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_one_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         Ok(Dynamic::from(add_one_to(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -579,13 +593,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_one_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         Ok(Dynamic::from(add_one_to(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -651,13 +666,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_one_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         Ok(Dynamic::from(add_one_to(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
 
                 #[allow(non_camel_case_types)]
@@ -670,7 +686,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_n_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         let arg1 = mem::take(args[1usize]).cast::<INT>();
                         Ok(Dynamic::from(add_n_to(arg0, arg1)))
@@ -678,6 +694,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -729,7 +746,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_together_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         let arg1 = mem::take(args[1usize]).cast::<INT>();
                         Ok(Dynamic::from(add_together(arg0, arg1)))
@@ -737,6 +754,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -795,7 +813,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for add_together_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).cast::<INT>();
                         let arg1 = mem::take(args[1usize]).cast::<INT>();
                         Ok(Dynamic::from(add_together(arg0, arg1)))
@@ -803,6 +821,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -871,13 +890,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_mystic_number_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = &mut args[0usize].write_lock::<Hello>().unwrap();
                         Ok(Dynamic::from(get_mystic_number(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1081,12 +1101,13 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_mystic_number_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         Ok(Dynamic::from(get_mystic_number()))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1171,13 +1192,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for print_out_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).into_immutable_string().unwrap();
                         Ok(Dynamic::from(print_out_to(&arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1229,13 +1251,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for print_out_to_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = mem::take(args[0usize]).into_string().unwrap();
                         Ok(Dynamic::from(print_out_to(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { false }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1288,7 +1311,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for foo_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<INT>();
                         let arg0 = &mut args[0usize].write_lock::<FLOAT>().unwrap();
                         Ok(Dynamic::from(foo(arg0, arg1)))
@@ -1296,6 +1319,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { true }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1347,13 +1371,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for increment_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = &mut args[0usize].write_lock::<FLOAT>().unwrap();
                         Ok(Dynamic::from(increment(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1408,13 +1433,14 @@ mod generate_tests {
                     }
                     impl PluginFunction for increment_token {
                         #[inline(always)]
-                        fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                        fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                             let arg0 = &mut args[0usize].write_lock::<FLOAT>().unwrap();
                             Ok(Dynamic::from(increment(arg0)))
                         }
 
                         #[inline(always)] fn is_method_call(&self) -> bool { true }
                         #[inline(always)] fn is_pure(&self) -> bool { false }
+                        #[inline(always)] fn has_context(&self) -> bool { false }
                     }
                 }
                 #[allow(unused_imports)]
@@ -1492,13 +1518,14 @@ mod generate_tests {
                     }
                     impl PluginFunction for increment_token {
                         #[inline(always)]
-                        fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                        fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                             let arg0 = &mut args[0usize].write_lock::<FLOAT>().unwrap();
                             Ok(Dynamic::from(increment(arg0)))
                         }
 
                         #[inline(always)] fn is_method_call(&self) -> bool { true }
                         #[inline(always)] fn is_pure(&self) -> bool { false }
+                        #[inline(always)] fn has_context(&self) -> bool { false }
                     }
                 }
                 #[allow(unused_imports)]
@@ -1577,13 +1604,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for int_foo_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = &mut args[0usize].write_lock::<u64>().unwrap();
                         Ok(Dynamic::from(int_foo(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1639,13 +1667,14 @@ mod generate_tests {
                 }
                 impl PluginFunction for int_foo_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg0 = &mut args[0usize].write_lock::<u64>().unwrap();
                         Ok(Dynamic::from(int_foo(arg0)))
                     }
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1698,7 +1727,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for int_foo_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg0 = &mut args[0usize].write_lock::<u64>().unwrap();
                         Ok(Dynamic::from(int_foo(arg0, arg1)))
@@ -1706,6 +1735,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1761,7 +1791,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for int_foo_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg0 = &mut args[0usize].write_lock::<u64>().unwrap();
                         Ok(Dynamic::from(int_foo(arg0, arg1)))
@@ -1769,6 +1799,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1821,7 +1852,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_by_index_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg0 = &mut args[0usize].write_lock::<MyCollection>().unwrap();
                         Ok(Dynamic::from(get_by_index(arg0, arg1)))
@@ -1829,6 +1860,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1889,7 +1921,7 @@ mod generate_tests {
                 #[cfg(hello)]
                 impl PluginFunction for get_by_index_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg0 = &mut args[0usize].write_lock::<MyCollection>().unwrap();
                         Ok(Dynamic::from(get_by_index(arg0, arg1)))
@@ -1897,6 +1929,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -1952,7 +1985,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for get_by_index_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg0 = &mut args[0usize].write_lock::<MyCollection>().unwrap();
                         Ok(Dynamic::from(get_by_index(arg0, arg1)))
@@ -1960,6 +1993,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -2012,7 +2046,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for set_by_index_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg2 = mem::take(args[2usize]).cast::<FLOAT>();
                         let arg0 = &mut args[0usize].write_lock::<MyCollection>().unwrap();
@@ -2021,6 +2055,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };
@@ -2076,7 +2111,7 @@ mod generate_tests {
                 }
                 impl PluginFunction for set_by_index_token {
                     #[inline(always)]
-                    fn call(&self, context: NativeCallContext, args: &mut [&mut Dynamic]) -> RhaiResult {
+                    fn call(&self, context: Option<NativeCallContext>, args: &mut [&mut Dynamic]) -> RhaiResult {
                         let arg1 = mem::take(args[1usize]).cast::<u64>();
                         let arg2 = mem::take(args[2usize]).cast::<FLOAT>();
                         let arg0 = &mut args[0usize].write_lock::<MyCollection>().unwrap();
@@ -2085,6 +2120,7 @@ mod generate_tests {
 
                     #[inline(always)] fn is_method_call(&self) -> bool { true }
                     #[inline(always)] fn is_pure(&self) -> bool { false }
+                    #[inline(always)] fn has_context(&self) -> bool { false }
                 }
             }
         };

examples/event_handler_js/script.rhai

@@ -4,7 +4,7 @@
 fn init() {
     // Can detect system-provided default states!
     // Add 'bool_state' as new state variable if one does not exist
-    if !("bool_state" in this) {
+    if "bool_state" !in this {
         this.bool_state = false;
     }
     // Add 'value' as new state variable (overwrites any existing)

examples/event_handler_map/script.rhai

@@ -4,7 +4,7 @@
 /// State is stored inside an object map bound to 'state'.
 fn init() {
     // Add 'bool_state' as new state variable if one does not exist
-    if !("bool_state" in state) {
+    if "bool_state" !in state {
         state.bool_state = false;
     }
     // Add 'obj_state' as new state variable (overwrites any existing)
@@ -37,7 +37,7 @@ fn start(data) {
 
 /// 'end' event handler
 fn end(data) {
-    if !state.bool_state || !("start_mode" in state) {
+    if !state.bool_state || "start_mode" !in state {
         throw "Not yet started!";
     }
     if state.value > 0 {

src/api/build_type.rs

@@ -88,6 +88,7 @@ impl Engine {
 ///
 /// To define a pretty-print name, call [`with_name`][`TypeBuilder::with_name`],
 /// to use [`Engine::register_type_with_name`] instead.
+#[must_use]
 pub struct TypeBuilder<'a, T: Variant + Clone> {
     engine: &'a mut Engine,
     name: Option<&'static str>,
@@ -101,7 +102,7 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
         Self {
             engine,
             name: None,
-            _marker: PhantomData::default(),
+            _marker: PhantomData,
         }
     }
 }
@@ -116,10 +117,10 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
 
     /// Register a custom function.
     #[inline(always)]
-    pub fn with_fn<A, R, S>(
+    pub fn with_fn<A: 'static, const N: usize, const C: bool, R: Variant + Clone, const L: bool>(
         &mut self,
         name: impl AsRef<str> + Into<Identifier>,
-        method: impl RegisterNativeFunction<A, R, S>,
+        method: impl RegisterNativeFunction<A, N, C, R, L>,
     ) -> &mut Self {
         self.engine.register_fn(name, method);
         self
@@ -148,10 +149,10 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under `no_object`.
     #[inline(always)]
-    pub fn with_get<V: Variant + Clone, S>(
+    pub fn with_get<const C: bool, V: Variant + Clone, const L: bool>(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, S> + crate::func::SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C, V, L> + crate::func::SendSync + 'static,
     ) -> &mut Self {
         self.engine.register_get(name, get_fn);
         self
@@ -161,10 +162,10 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under `no_object`.
     #[inline(always)]
-    pub fn with_set<V: Variant + Clone, S>(
+    pub fn with_set<const C: bool, V: Variant + Clone, const L: bool>(
         &mut self,
         name: impl AsRef<str>,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), S> + crate::func::SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C, (), L> + crate::func::SendSync + 'static,
     ) -> &mut Self {
         self.engine.register_set(name, set_fn);
         self
@@ -176,11 +177,19 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under `no_object`.
     #[inline(always)]
-    pub fn with_get_set<V: Variant + Clone, S1, S2>(
+    pub fn with_get_set<
+        const C1: bool,
+        const C2: bool,
+        V: Variant + Clone,
+        const L1: bool,
+        const L2: bool,
+    >(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, S1> + crate::func::SendSync + 'static,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), S2> + crate::func::SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C1, V, L1> + crate::func::SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C2, (), L2>
+            + crate::func::SendSync
+            + 'static,
     ) -> &mut Self {
         self.engine.register_get_set(name, get_fn, set_fn);
         self
@@ -195,9 +204,14 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under both `no_index` and `no_object`.
     #[inline(always)]
-    pub fn with_indexer_get<X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn with_indexer_get<
+        X: Variant + Clone,
+        const C: bool,
+        V: Variant + Clone,
+        const L: bool,
+    >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, S> + crate::func::SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C, V, L> + crate::func::SendSync + 'static,
     ) -> &mut Self {
         self.engine.register_indexer_get(get_fn);
         self
@@ -207,9 +221,16 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under both `no_index` and `no_object`.
     #[inline(always)]
-    pub fn with_indexer_set<X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn with_indexer_set<
+        X: Variant + Clone,
+        const C: bool,
+        V: Variant + Clone,
+        const L: bool,
+    >(
         &mut self,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), S> + crate::func::SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C, (), L>
+            + crate::func::SendSync
+            + 'static,
     ) -> &mut Self {
         self.engine.register_indexer_set(set_fn);
         self
@@ -219,10 +240,19 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     ///
     /// Not available under both `no_index` and `no_object`.
     #[inline(always)]
-    pub fn with_indexer_get_set<X: Variant + Clone, V: Variant + Clone, S1, S2>(
+    pub fn with_indexer_get_set<
+        X: Variant + Clone,
+        const C1: bool,
+        const C2: bool,
+        V: Variant + Clone,
+        const L1: bool,
+        const L2: bool,
+    >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, S1> + crate::func::SendSync + 'static,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), S2> + crate::func::SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C1, V, L1> + crate::func::SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C2, (), L2>
+            + crate::func::SendSync
+            + 'static,
     ) -> &mut Self {
         self.engine.register_indexer_get_set(get_fn, set_fn);
         self

src/api/call_fn.rs

@@ -3,10 +3,8 @@
 
 use crate::eval::{Caches, GlobalRuntimeState};
 use crate::types::dynamic::Variant;
-use crate::types::RestoreOnDrop;
 use crate::{
-    reify, Dynamic, Engine, FuncArgs, Position, RhaiResult, RhaiResultOf, Scope, StaticVec, AST,
-    ERR,
+    Dynamic, Engine, FuncArgs, Position, RhaiResult, RhaiResultOf, Scope, StaticVec, AST, ERR,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -81,7 +79,7 @@ impl Engine {
     ///
     /// The [`AST`] is evaluated before calling the function.
     /// This allows a script to load the necessary modules.
-    /// This is usually desired. If not, use [`call_fn_with_options`] instead.
+    /// This is usually desired. If not, use [`call_fn_with_options`][Engine::call_fn_with_options] instead.
     ///
     /// # Example
     ///
@@ -240,10 +238,10 @@ impl Engine {
         let rewind_scope = options.rewind_scope;
 
         let result = if options.eval_ast && !statements.is_empty() {
+            auto_restore! {
+                scope if rewind_scope => rewind;
                 let orig_scope_len = scope.len();
-            let scope = &mut *RestoreOnDrop::lock_if(rewind_scope, scope, move |s| {
-                s.rewind(orig_scope_len);
-            });
+            }
 
             self.eval_global_statements(global, caches, scope, statements)
         } else {
@@ -254,7 +252,7 @@ impl Engine {
 
             // Check for data race.
             #[cfg(not(feature = "no_closure"))]
-            crate::func::ensure_no_data_race(name, args, false).map(|_| Dynamic::UNIT)?;
+            crate::func::ensure_no_data_race(name, args, false)?;
 
             ast.shared_lib()
                 .get_script_fn(name, args.len())
@@ -276,7 +274,7 @@ impl Engine {
         });
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             global.debugger_mut().status = crate::eval::DebuggerStatus::Terminate;
             let node = &crate::ast::Stmt::Noop(Position::NONE);
             self.run_debugger(global, caches, scope, this_ptr, node)?;

src/api/compile.rs

@@ -218,15 +218,12 @@ impl Engine {
         scripts: impl AsRef<[S]>,
         optimization_level: OptimizationLevel,
     ) -> ParseResult<AST> {
-        let (stream, tokenizer_control) = self.lex_raw(
-            scripts.as_ref(),
-            self.token_mapper.as_ref().map(<_>::as_ref),
-        );
+        let (stream, tc) = self.lex_raw(scripts.as_ref(), self.token_mapper.as_deref());
         let interned_strings = &mut *locked_write(&self.interned_strings);
-        let mut state = ParseState::new(scope, interned_strings, tokenizer_control);
-        let mut _ast = self.parse(&mut stream.peekable(), &mut state, optimization_level)?;
+        let state = &mut ParseState::new(scope, interned_strings, tc);
+        let mut _ast = self.parse(stream.peekable(), state, optimization_level)?;
         #[cfg(feature = "metadata")]
-        _ast.set_doc(state.tokenizer_control.borrow().global_comments.join("\n"));
+        _ast.set_doc(&state.tokenizer_control.borrow().global_comments);
         Ok(_ast)
     }
     /// Compile a string containing an expression into an [`AST`],
@@ -292,12 +289,9 @@ impl Engine {
         script: impl AsRef<str>,
     ) -> ParseResult<AST> {
         let scripts = [script];
-        let (stream, tokenizer_control) =
-            self.lex_raw(&scripts, self.token_mapper.as_ref().map(<_>::as_ref));
-
-        let mut peekable = stream.peekable();
+        let (stream, t) = self.lex_raw(&scripts, self.token_mapper.as_deref());
         let interned_strings = &mut *locked_write(&self.interned_strings);
-        let mut state = ParseState::new(scope, interned_strings, tokenizer_control);
-        self.parse_global_expr(&mut peekable, &mut state, |_| {}, self.optimization_level)
+        let state = &mut ParseState::new(scope, interned_strings, t);
+        self.parse_global_expr(stream.peekable(), state, |_| {}, self.optimization_level)
     }
 }

src/api/custom_syntax.rs

@@ -4,11 +4,11 @@
 use crate::ast::Expr;
 use crate::func::SendSync;
 use crate::parser::ParseResult;
-use crate::tokenizer::{is_valid_identifier, Token};
+use crate::tokenizer::{is_valid_identifier, Token, NO_TOKEN};
 use crate::types::dynamic::Variant;
 use crate::{
-    reify, Dynamic, Engine, EvalContext, Identifier, ImmutableString, LexError, Position,
-    RhaiResult, StaticVec,
+    Dynamic, Engine, EvalContext, Identifier, ImmutableString, LexError, Position, RhaiResult,
+    StaticVec,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -166,6 +166,7 @@ impl Deref for Expression<'_> {
     type Target = Expr;
 
     #[inline(always)]
+    #[must_use]
     fn deref(&self) -> &Self::Target {
         self.0
     }
@@ -230,11 +231,11 @@ impl Engine {
                 continue;
             }
 
-            let token = Token::lookup_symbol_from_syntax(s).or_else(|| {
+            let token = Token::lookup_symbol_from_syntax(s).unwrap_or_else(|| {
                 if Token::is_reserved_keyword(s) {
-                    Some(Token::Reserved(Box::new(s.into())))
+                    Token::Reserved(Box::new(s.into()))
                 } else {
-                    None
+                    NO_TOKEN
                 }
             });
 
@@ -255,16 +256,16 @@ impl Engine {
                 #[cfg(not(feature = "no_float"))]
                 CUSTOM_SYNTAX_MARKER_FLOAT if !segments.is_empty() => s.into(),
                 // Standard or reserved keyword/symbol not in first position
-                _ if !segments.is_empty() && token.is_some() => {
+                _ if !segments.is_empty() && token != NO_TOKEN => {
                     // Make it a custom keyword/symbol if it is disabled or reserved
                     if (self
                         .disabled_symbols
-                        .as_ref()
+                        .as_deref()
                         .map_or(false, |m| m.contains(s))
-                        || token.map_or(false, |v| v.is_reserved()))
+                        || token.is_reserved())
                         && !self
                             .custom_keywords
-                            .as_ref()
+                            .as_deref()
                             .map_or(false, |m| m.contains_key(s))
                     {
                         self.custom_keywords
@@ -275,10 +276,10 @@ impl Engine {
                 }
                 // Standard keyword in first position but not disabled
                 _ if segments.is_empty()
-                    && token.as_ref().map_or(false, Token::is_standard_keyword)
+                    && token.is_standard_keyword()
                     && !self
                         .disabled_symbols
-                        .as_ref()
+                        .as_deref()
                         .map_or(false, |m| m.contains(s)) =>
                 {
                     return Err(LexError::ImproperSymbol(
@@ -295,12 +296,12 @@ impl Engine {
                     // Make it a custom keyword/symbol if it is disabled or reserved
                     if self
                         .disabled_symbols
-                        .as_ref()
+                        .as_deref()
                         .map_or(false, |m| m.contains(s))
-                        || (token.map_or(false, |v| v.is_reserved())
+                        || (token.is_reserved()
                             && !self
                                 .custom_keywords
-                                .as_ref()
+                                .as_deref()
                                 .map_or(false, |m| m.contains_key(s)))
                     {
                         self.custom_keywords

src/api/definitions/mod.rs

@@ -29,6 +29,7 @@ impl Engine {
     /// # }
     /// ```
     #[inline(always)]
+    #[must_use]
     pub fn definitions(&self) -> Definitions {
         Definitions {
             engine: self,
@@ -55,6 +56,7 @@ impl Engine {
     /// # }
     /// ```
     #[inline(always)]
+    #[must_use]
     pub fn definitions_with_scope<'e>(&'e self, scope: &'e Scope<'e>) -> Definitions<'e> {
         Definitions {
             engine: self,
@@ -67,7 +69,6 @@ impl Engine {
 /// Internal configuration for module generation.
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
 #[non_exhaustive]
-#[must_use]
 pub struct DefinitionsConfig {
     /// Write `module ...` headers in definition files (default `false`).
     pub write_headers: bool,
@@ -77,6 +78,7 @@ pub struct DefinitionsConfig {
 
 impl Default for DefinitionsConfig {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self {
             write_headers: false,
@@ -89,7 +91,6 @@ impl Default for DefinitionsConfig {
 /// contents of an [`Engine`].
 /// Exported under the `internals` and `metadata` feature only.
 #[derive(Debug, Clone)]
-#[must_use]
 pub struct Definitions<'e> {
     /// The [`Engine`].
     engine: &'e Engine,
@@ -104,12 +105,14 @@ impl Definitions<'_> {
     /// Headers are always present in content that is expected to be written to a file
     /// (i.e. `write_to*` and `*_file` methods).
     #[inline(always)]
+    #[must_use]
     pub const fn with_headers(mut self, headers: bool) -> Self {
         self.config.write_headers = headers;
         self
     }
     /// Include standard packages when writing definition files.
     #[inline(always)]
+    #[must_use]
     pub const fn include_standard_packages(mut self, include_standard_packages: bool) -> Self {
         self.config.include_standard_packages = include_standard_packages;
         self
@@ -128,6 +131,7 @@ impl Definitions<'_> {
     }
     /// Get the configuration.
     #[inline(always)]
+    #[must_use]
     pub(crate) const fn config(&self) -> &DefinitionsConfig {
         &self.config
     }
@@ -368,8 +372,9 @@ impl Definitions<'_> {
         let mut m = self
             .engine
             .global_sub_modules
-            .iter()
-            .flat_map(|m| m.iter())
+            .as_deref()
+            .into_iter()
+            .flatten()
             .map(move |(name, module)| {
                 (
                     name.to_string(),
@@ -391,6 +396,7 @@ impl Definitions<'_> {
 impl Module {
     /// Return definitions for all items inside the [`Module`].
     #[cfg(not(feature = "no_module"))]
+    #[must_use]
     fn definition(&self, def: &Definitions) -> String {
         let mut s = String::new();
         self.write_definition(&mut s, def).unwrap();
@@ -455,7 +461,7 @@ impl Module {
                     || def
                         .engine
                         .custom_keywords
-                        .as_ref()
+                        .as_deref()
                         .map_or(false, |m| m.contains_key(f.metadata.name.as_str()));
 
                 f.write_definition(writer, def, operator)?;
@@ -536,6 +542,7 @@ impl FuncInfo {
 /// It tries to flatten types, removing `&` and `&mut`, and paths, while keeping generics.
 ///
 /// Associated generic types are also rewritten into regular generic type parameters.
+#[must_use]
 fn def_type_name<'a>(ty: &'a str, engine: &'a Engine) -> Cow<'a, str> {
     let ty = engine.format_type_name(ty).replace("crate::", "");
     let ty = ty.strip_prefix("&mut").unwrap_or(&*ty).trim();

src/api/deprecated.rs

@@ -26,7 +26,7 @@ impl Engine {
     ///
     /// This method is deprecated. Use [`run_file`][Engine::run_file] instead.
     ///
-    /// This method will be removed in the next majocd cr version.
+    /// This method will be removed in the next major version.
     #[deprecated(since = "1.1.0", note = "use `run_file` instead")]
     #[cfg(not(feature = "no_std"))]
     #[cfg(not(target_family = "wasm"))]
@@ -137,12 +137,6 @@ impl Engine {
     }
     /// Call a script function defined in an [`AST`] with multiple [`Dynamic`] arguments.
     ///
-    /// The following options are available:
-    ///
-    /// * whether to evaluate the [`AST`] to load necessary modules before calling the function
-    /// * whether to rewind the [`Scope`] after the function call
-    /// * a value for binding to the `this` pointer (if any)
-    ///
     /// Not available under `no_function`.
     ///
     /// # Deprecated
@@ -191,10 +185,10 @@ impl Engine {
     /// This method will be removed in the next major version.
     #[deprecated(since = "1.9.1", note = "use `register_fn` instead")]
     #[inline(always)]
-    pub fn register_result_fn<A, R, S>(
+    pub fn register_result_fn<A: 'static, const N: usize, const C: bool, R: Variant + Clone>(
         &mut self,
         name: impl AsRef<str> + Into<Identifier>,
-        func: impl RegisterNativeFunction<A, R, RhaiResultOf<S>>,
+        func: impl RegisterNativeFunction<A, N, C, R, true>,
     ) -> &mut Self {
         self.register_fn(name, func)
     }
@@ -212,12 +206,10 @@ impl Engine {
     #[deprecated(since = "1.9.1", note = "use `register_get` instead")]
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn register_get_result<T: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_get_result<T: Variant + Clone, const C: bool, V: Variant + Clone>(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, RhaiResultOf<S>>
-            + crate::func::SendSync
-            + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C, V, true> + crate::func::SendSync + 'static,
     ) -> &mut Self {
         self.register_get(name, get_fn)
     }
@@ -233,10 +225,10 @@ impl Engine {
     #[deprecated(since = "1.9.1", note = "use `register_set` instead")]
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn register_set_result<T: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_set_result<T: Variant + Clone, V: Variant + Clone, const C: bool, S>(
         &mut self,
         name: impl AsRef<str>,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), RhaiResultOf<S>>
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C, (), true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {
@@ -253,12 +245,6 @@ impl Engine {
     /// This method is deprecated. Use [`register_indexer_get`][Engine::register_indexer_get] instead.
     ///
     /// This method will be removed in the next major version.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the type is [`Array`][crate::Array], [`Map`][crate::Map], [`String`],
-    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
-    /// Indexers for arrays, object maps, strings and integers cannot be registered.
     #[deprecated(since = "1.9.1", note = "use `register_indexer_get` instead")]
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline(always)]
@@ -266,10 +252,10 @@ impl Engine {
         T: Variant + Clone,
         X: Variant + Clone,
         V: Variant + Clone,
-        S,
+        const C: bool,
     >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, RhaiResultOf<S>>
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C, V, true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {
@@ -284,12 +270,6 @@ impl Engine {
     /// This method is deprecated. Use [`register_indexer_set`][Engine::register_indexer_set] instead.
     ///
     /// This method will be removed in the next major version.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the type is [`Array`][crate::Array], [`Map`][crate::Map], [`String`],
-    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
-    /// Indexers for arrays, object maps, strings and integers cannot be registered.
     #[deprecated(since = "1.9.1", note = "use `register_indexer_set` instead")]
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline(always)]
@@ -297,10 +277,10 @@ impl Engine {
         T: Variant + Clone,
         X: Variant + Clone,
         V: Variant + Clone,
-        S,
+        const C: bool,
     >(
         &mut self,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), RhaiResultOf<S>>
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C, (), true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {
@@ -316,34 +296,6 @@ impl Engine {
     /// Use [`register_custom_syntax_with_state_raw`][Engine::register_custom_syntax_with_state_raw] instead.
     ///
     /// This method will be removed in the next major version.
-    ///
-    /// # WARNING - Low Level API
-    ///
-    /// This function is very low level.
-    ///
-    /// * `scope_may_be_changed` specifies variables have been added/removed by this custom syntax.
-    /// * `parse` is the parsing function.
-    /// * `func` is the implementation function.
-    ///
-    /// All custom keywords used as symbols must be manually registered via [`Engine::register_custom_operator`].
-    /// Otherwise, they won't be recognized.
-    ///
-    /// # Parsing Function Signature
-    ///
-    /// The parsing function has the following signature:
-    ///
-    /// `Fn(symbols: &[ImmutableString], look_ahead: &str) -> Result<Option<ImmutableString>, ParseError>`
-    ///
-    /// where:
-    /// * `symbols`: a slice of symbols that have been parsed so far, possibly containing `$expr$` and/or `$block$`;
-    ///   `$ident$` and other literal markers are replaced by the actual text
-    /// * `look_ahead`: a string slice containing the next symbol that is about to be read
-    ///
-    /// ## Return value
-    ///
-    /// * `Ok(None)`: parsing complete and there are no more symbols to match.
-    /// * `Ok(Some(symbol))`: the next symbol to match, which can also be `$expr$`, `$ident$` or `$block$`.
-    /// * `Err(ParseError)`: error that is reflected back to the [`Engine`], normally `ParseError(ParseErrorType::BadInput(LexError::ImproperSymbol(message)), Position::NONE)` to indicate a syntax error, but it can be any [`ParseError`][crate::ParseError].
     #[deprecated(
         since = "1.11.0",
         note = "use `register_custom_syntax_with_state_raw` instead"
@@ -368,6 +320,24 @@ impl Engine {
             move |context, expressions, _| func(context, expressions),
         )
     }
+    /// _(internals)_ Evaluate a list of statements with no `this` pointer.
+    /// Exported under the `internals` feature only.
+    ///
+    /// # Deprecated
+    ///
+    /// This method is deprecated. It will be removed in the next major version.
+    #[cfg(feature = "internals")]
+    #[inline(always)]
+    #[deprecated(since = "1.12.0")]
+    pub fn eval_statements_raw(
+        &self,
+        global: &mut crate::eval::GlobalRuntimeState,
+        caches: &mut crate::eval::Caches,
+        scope: &mut Scope,
+        statements: &[crate::ast::Stmt],
+    ) -> RhaiResult {
+        self.eval_global_statements(global, caches, scope, statements)
+    }
 }
 
 impl Dynamic {
@@ -544,10 +514,15 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     /// This method will be removed in the next major version.
     #[deprecated(since = "1.9.1", note = "use `with_fn` instead")]
     #[inline(always)]
-    pub fn with_result_fn<N, A, F, R, S>(&mut self, name: N, method: F) -> &mut Self
+    pub fn with_result_fn<S, A: 'static, const N: usize, const C: bool, R, F>(
+        &mut self,
+        name: S,
+        method: F,
+    ) -> &mut Self
     where
-        N: AsRef<str> + Into<Identifier>,
-        F: RegisterNativeFunction<A, R, RhaiResultOf<S>>,
+        S: AsRef<str> + Into<Identifier>,
+        R: Variant + Clone,
+        F: RegisterNativeFunction<A, N, C, R, true>,
     {
         self.with_fn(name, method)
     }
@@ -566,12 +541,10 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     #[deprecated(since = "1.9.1", note = "use `with_get` instead")]
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn with_get_result<V: Variant + Clone, S>(
+    pub fn with_get_result<V: Variant + Clone, const C: bool>(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, RhaiResultOf<S>>
-            + crate::func::SendSync
-            + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C, V, true> + crate::func::SendSync + 'static,
     ) -> &mut Self {
         self.with_get(name, get_fn)
     }
@@ -588,10 +561,10 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     #[deprecated(since = "1.9.1", note = "use `with_set` instead")]
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn with_set_result<V: Variant + Clone, S>(
+    pub fn with_set_result<V: Variant + Clone, const C: bool>(
         &mut self,
         name: impl AsRef<str>,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), RhaiResultOf<S>>
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C, (), true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {
@@ -612,9 +585,9 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     #[deprecated(since = "1.9.1", note = "use `with_indexer_get` instead")]
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline(always)]
-    pub fn with_indexer_get_result<X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn with_indexer_get_result<X: Variant + Clone, V: Variant + Clone, const C: bool>(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, RhaiResultOf<S>>
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C, V, true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {
@@ -633,9 +606,9 @@ impl<'a, T: Variant + Clone> TypeBuilder<'a, T> {
     #[deprecated(since = "1.9.1", note = "use `with_indexer_set` instead")]
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline(always)]
-    pub fn with_indexer_set_result<X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn with_indexer_set_result<X: Variant + Clone, V: Variant + Clone, const C: bool>(
         &mut self,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), RhaiResultOf<S>>
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C, (), true>
             + crate::func::SendSync
             + 'static,
     ) -> &mut Self {

src/api/eval.rs

@@ -5,7 +5,7 @@ use crate::func::native::locked_write;
 use crate::parser::ParseState;
 use crate::types::dynamic::Variant;
 use crate::{
-    reify, Dynamic, Engine, OptimizationLevel, Position, RhaiResult, RhaiResultOf, Scope, AST, ERR,
+    Dynamic, Engine, OptimizationLevel, Position, RhaiResult, RhaiResultOf, Scope, AST, ERR,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -121,15 +121,14 @@ impl Engine {
         let ast = {
             let interned_strings = &mut *locked_write(&self.interned_strings);
 
-            let (stream, tokenizer_control) =
-                self.lex_raw(&scripts, self.token_mapper.as_ref().map(<_>::as_ref));
+            let (stream, tc) = self.lex_raw(&scripts, self.token_mapper.as_deref());
 
-            let mut state = ParseState::new(scope, interned_strings, tokenizer_control);
+            let state = &mut ParseState::new(scope, interned_strings, tc);
 
             // No need to optimize a lone expression
             self.parse_global_expr(
-                &mut stream.peekable(),
-                &mut state,
+                stream.peekable(),
+                state,
                 |_| {},
                 #[cfg(not(feature = "no_optimize"))]
                 OptimizationLevel::None,
@@ -243,7 +242,7 @@ impl Engine {
         let result = self.eval_global_statements(global, caches, scope, statements);
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             global.debugger_mut().status = crate::eval::DebuggerStatus::Terminate;
             let mut this = Dynamic::NULL;
             let node = &crate::ast::Stmt::Noop(Position::NONE);
@@ -263,25 +262,6 @@ impl Engine {
 
         result
     }
-    /// _(internals)_ Evaluate a list of statements with no `this` pointer.
-    /// Exported under the `internals` feature only.
-    ///
-    /// This is commonly used to evaluate a list of statements in an [`AST`] or a script function body.
-    ///
-    /// # WARNING - Low Level API
-    ///
-    /// This function is very low level.
-    #[cfg(feature = "internals")]
-    #[inline(always)]
-    pub fn eval_statements_raw(
-        &self,
-        global: &mut GlobalRuntimeState,
-        caches: &mut Caches,
-        scope: &mut Scope,
-        statements: &[crate::ast::Stmt],
-    ) -> RhaiResult {
-        self.eval_global_statements(global, caches, scope, statements)
-    }
 }
 
 /// Evaluate a string as a script, returning the result value or an error.

src/api/events.rs

@@ -349,7 +349,9 @@ impl Engine {
     #[inline(always)]
     pub fn register_debugger(
         &mut self,
-        init: impl Fn(&Self) -> Dynamic + SendSync + 'static,
+        init: impl Fn(&Self, crate::debugger::Debugger) -> crate::debugger::Debugger
+            + SendSync
+            + 'static,
         callback: impl Fn(
                 EvalContext,
                 crate::eval::DebuggerEvent,
@@ -360,7 +362,7 @@ impl Engine {
             + SendSync
             + 'static,
     ) -> &mut Self {
-        self.debugger = Some(Box::new((Box::new(init), Box::new(callback))));
+        self.debugger_interface = Some(Box::new((Box::new(init), Box::new(callback))));
         self
     }
 }

src/api/json.rs

@@ -64,8 +64,8 @@ impl Engine {
 
         let (stream, tokenizer_control) = self.lex_raw(
             &scripts,
-            if has_null {
-                Some(&|token, _, _| {
+            Some(if has_null {
+                &|token, _, _| {
                     match token {
                         // `null` => `()`
                         Token::Reserved(s) if &*s == "null" => Token::Unit,
@@ -86,9 +86,9 @@ impl Engine {
                         // All others
                         _ => token,
                     }
-                })
+                }
             } else {
-                Some(&|token, _, _| {
+                &|token, _, _| {
                     match token {
                         Token::Reserved(s) if &*s == "null" => Token::LexError(
                             LexError::ImproperSymbol("null".to_string(), String::new()).into(),
@@ -97,34 +97,31 @@ impl Engine {
                         Token::LeftBrace => Token::MapStart,
                         // Disallowed syntax
                         t @ (Token::Unit | Token::MapStart) => Token::LexError(
-                            LexError::ImproperSymbol(
-                                t.literal_syntax().to_string(),
-                                "Invalid JSON syntax".to_string(),
-                            )
+                            LexError::ImproperSymbol(t.literal_syntax().to_string(), String::new())
                                 .into(),
                         ),
                         Token::InterpolatedString(..) => Token::LexError(
                             LexError::ImproperSymbol(
                                 "interpolated string".to_string(),
-                                "Invalid JSON syntax".to_string(),
+                                String::new(),
                             )
                             .into(),
                         ),
                         // All others
                         _ => token,
                     }
-                })
-            },
+                }
+            }),
         );
 
         let ast = {
             let scope = Scope::new();
             let interned_strings = &mut *locked_write(&self.interned_strings);
-            let mut state = ParseState::new(&scope, interned_strings, tokenizer_control);
+            let state = &mut ParseState::new(&scope, interned_strings, tokenizer_control);
 
             self.parse_global_expr(
-                &mut stream.peekable(),
-                &mut state,
+                stream.peekable(),
+                state,
                 |s| s.flags |= ParseSettingFlags::DISALLOW_UNQUOTED_MAP_PROPERTIES,
                 #[cfg(not(feature = "no_optimize"))]
                 OptimizationLevel::None,

src/api/limits.rs

@@ -6,23 +6,20 @@ use std::num::{NonZeroU64, NonZeroUsize};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
-pub mod default_limits {
 #[cfg(debug_assertions)]
+pub mod default_limits {
     #[cfg(not(feature = "no_function"))]
     pub const MAX_CALL_STACK_DEPTH: usize = 8;
-    #[cfg(debug_assertions)]
     pub const MAX_EXPR_DEPTH: usize = 32;
     #[cfg(not(feature = "no_function"))]
-    #[cfg(debug_assertions)]
     pub const MAX_FUNCTION_EXPR_DEPTH: usize = 16;
-
+}
 #[cfg(not(debug_assertions))]
+pub mod default_limits {
     #[cfg(not(feature = "no_function"))]
     pub const MAX_CALL_STACK_DEPTH: usize = 64;
-    #[cfg(not(debug_assertions))]
     pub const MAX_EXPR_DEPTH: usize = 64;
     #[cfg(not(feature = "no_function"))]
-    #[cfg(not(debug_assertions))]
     pub const MAX_FUNCTION_EXPR_DEPTH: usize = 32;
 }
 
@@ -55,7 +52,7 @@ pub struct Limits {
     #[cfg(not(feature = "no_module"))]
     pub max_modules: usize,
     /// Maximum length of a [string][crate::ImmutableString].
-    pub max_string_size: Option<NonZeroUsize>,
+    pub max_string_len: Option<NonZeroUsize>,
     /// Maximum length of an [array][crate::Array].
     ///
     /// Not available under `no_index`.
@@ -83,7 +80,7 @@ impl Limits {
             max_operations: None,
             #[cfg(not(feature = "no_module"))]
             max_modules: usize::MAX,
-            max_string_size: None,
+            max_string_len: None,
             #[cfg(not(feature = "no_index"))]
             max_array_size: None,
             #[cfg(not(feature = "no_object"))]
@@ -104,7 +101,7 @@ impl Engine {
     /// Is there a data size limit set?
     #[inline(always)]
     pub(crate) const fn has_data_size_limit(&self) -> bool {
-        self.limits.max_string_size.is_some()
+        self.limits.max_string_len.is_some()
             || {
                 #[cfg(not(feature = "no_index"))]
                 {
@@ -222,19 +219,19 @@ impl Engine {
         #[cfg(feature = "no_function")]
         return 0;
     }
-    /// Set the maximum length of [strings][crate::ImmutableString] (0 for unlimited).
+    /// Set the maximum length, in bytes, of [strings][crate::ImmutableString] (0 for unlimited).
     ///
     /// Not available under `unchecked`.
     #[inline(always)]
-    pub fn set_max_string_size(&mut self, max_size: usize) -> &mut Self {
-        self.limits.max_string_size = NonZeroUsize::new(max_size);
+    pub fn set_max_string_size(&mut self, max_len: usize) -> &mut Self {
+        self.limits.max_string_len = NonZeroUsize::new(max_len);
         self
     }
-    /// The maximum length of [strings][crate::ImmutableString] (0 for unlimited).
+    /// The maximum length, in bytes, of [strings][crate::ImmutableString] (0 for unlimited).
     #[inline]
     #[must_use]
     pub const fn max_string_size(&self) -> usize {
-        match self.limits.max_string_size {
+        match self.limits.max_string_len {
             Some(n) => n.get(),
             None => 0,
         }

src/api/limits_unchecked.rs

@@ -0,0 +1,71 @@
+//! Placeholder settings for [`Engine`]'s limitations.
+#![cfg(feature = "unchecked")]
+
+use crate::Engine;
+
+impl Engine {
+    /// The maximum levels of function calls allowed for a script.
+    ///
+    /// Always returns [`usize::MAX`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_call_levels(&self) -> usize {
+        usize::MAX
+    }
+    /// The maximum number of operations allowed for a script to run (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_operations(&self) -> u64 {
+        0
+    }
+    /// The maximum number of imported [modules][crate::Module] allowed for a script.
+    ///
+    /// Always returns [`usize::MAX`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_modules(&self) -> usize {
+        usize::MAX
+    }
+    /// The depth limit for expressions (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_expr_depth(&self) -> usize {
+        0
+    }
+    /// The depth limit for expressions in functions (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_function_expr_depth(&self) -> usize {
+        0
+    }
+    /// The maximum length of [strings][crate::ImmutableString] (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_string_size(&self) -> usize {
+        0
+    }
+    /// The maximum length of [arrays][crate::Array] (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_array_size(&self) -> usize {
+        0
+    }
+    /// The maximum size of [object maps][crate::Map] (0 for unlimited).
+    ///
+    /// Always returns zero.
+    #[inline(always)]
+    #[must_use]
+    pub const fn max_map_size(&self) -> usize {
+        0
+    }
+}

src/api/mod.rs

@@ -1,7 +1,5 @@
 //! Module defining the public API of the Rhai engine.
 
-pub mod type_names;
-
 pub mod eval;
 
 pub mod run;
@@ -21,18 +19,21 @@ pub mod options;
 pub mod optimize;
 
 pub mod limits;
+pub mod limits_unchecked;
 
 pub mod events;
 
-pub mod custom_syntax;
+pub mod type_names;
 
-pub mod deprecated;
+pub mod custom_syntax;
 
 pub mod build_type;
 
 #[cfg(feature = "metadata")]
 pub mod definitions;
 
+pub mod deprecated;
+
 use crate::{Dynamic, Engine, Identifier};
 
 #[cfg(feature = "no_std")]
@@ -167,7 +168,7 @@ impl Engine {
             Some(token) if token.is_standard_keyword() => {
                 if !self
                     .disabled_symbols
-                    .as_ref()
+                    .as_deref()
                     .map_or(false, |m| m.contains(token.literal_syntax()))
                 {
                     return Err(format!("'{keyword}' is a reserved keyword"));
@@ -177,7 +178,7 @@ impl Engine {
             Some(token) if token.is_standard_symbol() => {
                 if !self
                     .disabled_symbols
-                    .as_ref()
+                    .as_deref()
                     .map_or(false, |m| m.contains(token.literal_syntax()))
                 {
                     return Err(format!("'{keyword}' is a reserved operator"));
@@ -187,7 +188,7 @@ impl Engine {
             Some(token)
                 if !self
                     .disabled_symbols
-                    .as_ref()
+                    .as_deref()
                     .map_or(false, |m| m.contains(token.literal_syntax())) =>
             {
                 return Err(format!("'{keyword}' is a reserved symbol"))
@@ -223,71 +224,3 @@ impl Engine {
         self
     }
 }
-
-#[cfg(feature = "unchecked")]
-impl Engine {
-    /// The maximum levels of function calls allowed for a script.
-    ///
-    /// Always returns [`usize::MAX`] under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_call_levels(&self) -> usize {
-        usize::MAX
-    }
-    /// The maximum number of operations allowed for a script to run (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_operations(&self) -> u64 {
-        0
-    }
-    /// The maximum number of imported [modules][crate::Module] allowed for a script.
-    ///
-    /// Always returns [`usize::MAX`] under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_modules(&self) -> usize {
-        usize::MAX
-    }
-    /// The depth limit for expressions (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_expr_depth(&self) -> usize {
-        0
-    }
-    /// The depth limit for expressions in functions (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_function_expr_depth(&self) -> usize {
-        0
-    }
-    /// The maximum length of [strings][crate::ImmutableString] (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_string_size(&self) -> usize {
-        0
-    }
-    /// The maximum length of [arrays][crate::Array] (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_array_size(&self) -> usize {
-        0
-    }
-    /// The maximum size of [object maps][crate::Map] (0 for unlimited).
-    ///
-    /// Always returns zero under `unchecked`.
-    #[inline(always)]
-    #[must_use]
-    pub const fn max_map_size(&self) -> usize {
-        0
-    }
-}

src/api/optimize.rs

@@ -51,20 +51,14 @@ impl Engine {
     ) -> AST {
         let mut ast = ast;
 
-        #[cfg(not(feature = "no_function"))]
-        let functions = ast
-            .shared_lib()
-            .iter_fn()
-            .filter(|f| f.func.is_script())
-            .map(|f| f.func.get_script_fn_def().unwrap().clone())
-            .collect();
-
-        let mut _new_ast = crate::optimizer::optimize_into_ast(
-            self,
+        let mut _new_ast = self.optimize_into_ast(
             scope,
             ast.take_statements(),
             #[cfg(not(feature = "no_function"))]
-            functions,
+            ast.shared_lib()
+                .iter_fn()
+                .map(|f| f.func.get_script_fn_def().cloned().expect("`ScriptFnDef"))
+                .collect(),
             optimization_level,
         );
 

src/api/register.rs

@@ -56,7 +56,14 @@ impl Engine {
     /// # }
     /// ```
     #[inline]
-    pub fn register_fn<A, R, S, F: RegisterNativeFunction<A, R, S>>(
+    pub fn register_fn<
+        A: 'static,
+        const N: usize,
+        const C: bool,
+        R: Variant + Clone,
+        const L: bool,
+        F: RegisterNativeFunction<A, N, C, R, L>,
+    >(
         &mut self,
         name: impl AsRef<str> + Into<Identifier>,
         func: F,
@@ -83,13 +90,24 @@ impl Engine {
         #[cfg(not(feature = "metadata"))]
         let param_type_names: Option<&[&str]> = None;
 
+        let fn_name = name.as_ref();
+        let no_const = false;
+
+        #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
+        let no_const = no_const || (F::num_params() == 3 && fn_name == crate::engine::FN_IDX_SET);
+        #[cfg(not(feature = "no_object"))]
+        let no_const =
+            no_const || (F::num_params() == 2 && fn_name.starts_with(crate::engine::FN_SET));
+
+        let func = func.into_callable_function(fn_name.into(), no_const);
+
         self.global_namespace_mut().set_fn(
             name,
             FnNamespace::Global,
             FnAccess::Public,
             param_type_names,
             param_types,
-            func.into_callable_function(),
+            func,
         );
         self
     }
@@ -299,10 +317,10 @@ impl Engine {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn register_get<T: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_get<T: Variant + Clone, const C: bool, V: Variant + Clone, const L: bool>(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, S> + SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C, V, L> + SendSync + 'static,
     ) -> &mut Self {
         self.register_fn(crate::engine::make_getter(name.as_ref()).as_str(), get_fn)
     }
@@ -349,10 +367,10 @@ impl Engine {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn register_set<T: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_set<T: Variant + Clone, const C: bool, V: Variant + Clone, const L: bool>(
         &mut self,
         name: impl AsRef<str>,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), S> + SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C, (), L> + SendSync + 'static,
     ) -> &mut Self {
         self.register_fn(crate::engine::make_setter(name.as_ref()).as_str(), set_fn)
     }
@@ -403,11 +421,18 @@ impl Engine {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn register_get_set<T: Variant + Clone, V: Variant + Clone, S1, S2>(
+    pub fn register_get_set<
+        T: Variant + Clone,
+        const C1: bool,
+        const C2: bool,
+        V: Variant + Clone,
+        const L1: bool,
+        const L2: bool,
+    >(
         &mut self,
         name: impl AsRef<str>,
-        get_fn: impl RegisterNativeFunction<(Mut<T>,), V, S1> + SendSync + 'static,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, V), (), S2> + SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>,), 1, C1, V, L1> + SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, V), 2, C2, (), L2> + SendSync + 'static,
     ) -> &mut Self {
         self.register_get(&name, get_fn).register_set(&name, set_fn)
     }
@@ -462,9 +487,15 @@ impl Engine {
     /// ```
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline]
-    pub fn register_indexer_get<T: Variant + Clone, X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_indexer_get<
+        T: Variant + Clone,
+        X: Variant + Clone,
+        const C: bool,
+        V: Variant + Clone,
+        const L: bool,
+    >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, S> + SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C, V, L> + SendSync + 'static,
     ) -> &mut Self {
         #[cfg(not(feature = "no_index"))]
         if TypeId::of::<T>() == TypeId::of::<crate::Array>() {
@@ -537,9 +568,15 @@ impl Engine {
     /// ```
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline]
-    pub fn register_indexer_set<T: Variant + Clone, X: Variant + Clone, V: Variant + Clone, S>(
+    pub fn register_indexer_set<
+        T: Variant + Clone,
+        X: Variant + Clone,
+        const C: bool,
+        V: Variant + Clone,
+        const L: bool,
+    >(
         &mut self,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), S> + SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C, (), L> + SendSync + 'static,
     ) -> &mut Self {
         #[cfg(not(feature = "no_index"))]
         if TypeId::of::<T>() == TypeId::of::<crate::Array>() {
@@ -616,13 +653,15 @@ impl Engine {
     pub fn register_indexer_get_set<
         T: Variant + Clone,
         X: Variant + Clone,
+        const C1: bool,
+        const C2: bool,
         V: Variant + Clone,
-        S1,
-        S2,
+        const L1: bool,
+        const L2: bool,
     >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<T>, X), V, S1> + SendSync + 'static,
-        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), (), S2> + SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<T>, X), 2, C1, V, L1> + SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<T>, X, V), 3, C2, (), L2> + SendSync + 'static,
     ) -> &mut Self {
         self.register_indexer_get(get_fn)
             .register_indexer_set(set_fn)
@@ -743,7 +782,7 @@ impl Engine {
         signatures.extend(self.global_namespace().gen_fn_signatures());
 
         #[cfg(not(feature = "no_module"))]
-        for (name, m) in self.global_sub_modules.iter().flat_map(|m| m.iter()) {
+        for (name, m) in self.global_sub_modules.as_deref().into_iter().flatten() {
             signatures.extend(m.gen_fn_signatures().map(|f| format!("{name}::{f}")));
         }
 

src/api/run.rs

@@ -58,14 +58,10 @@ impl Engine {
     pub fn run_with_scope(&self, scope: &mut Scope, script: &str) -> RhaiResultOf<()> {
         let scripts = [script];
         let ast = {
+            let (stream, tc) = self.lex_raw(&scripts, self.token_mapper.as_deref());
             let interned_strings = &mut *locked_write(&self.interned_strings);
-
-            let (stream, tokenizer_control) =
-                self.lex_raw(&scripts, self.token_mapper.as_ref().map(<_>::as_ref));
-
-            let mut state = ParseState::new(scope, interned_strings, tokenizer_control);
-
-            self.parse(&mut stream.peekable(), &mut state, self.optimization_level)?
+            let state = &mut ParseState::new(scope, interned_strings, tc);
+            self.parse(stream.peekable(), state, self.optimization_level)?
         };
         self.run_ast_with_scope(scope, &ast)
     }
@@ -131,19 +127,23 @@ impl Engine {
         }
 
         let statements = ast.statements();
-        if !statements.is_empty() {
-            self.eval_global_statements(global, caches, scope, statements)?;
-        }
+
+        let result = if !statements.is_empty() {
+            self.eval_global_statements(global, caches, scope, statements)
+                .map(|_| ())
+        } else {
+            Ok(())
+        };
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             global.debugger_mut().status = crate::eval::DebuggerStatus::Terminate;
             let mut this = crate::Dynamic::NULL;
             let node = &crate::ast::Stmt::Noop(crate::Position::NONE);
             self.run_debugger(global, caches, scope, &mut this, node)?;
         }
 
-        Ok(())
+        result
     }
 }
 

src/api/type_names.rs

@@ -204,8 +204,9 @@ impl Engine {
                 #[cfg(not(feature = "no_module"))]
                 return self
                     .global_sub_modules
-                    .iter()
-                    .flat_map(|m| m.iter())
+                    .as_deref()
+                    .into_iter()
+                    .flatten()
                     .find_map(|(_, m)| m.get_custom_type(name));
                 #[cfg(feature = "no_module")]
                 return None;
@@ -238,8 +239,9 @@ impl Engine {
                 #[cfg(not(feature = "no_module"))]
                 return self
                     .global_sub_modules
-                    .iter()
-                    .flat_map(|m| m.iter())
+                    .as_deref()
+                    .into_iter()
+                    .flatten()
                     .find_map(|(_, m)| m.get_custom_type(name));
                 #[cfg(feature = "no_module")]
                 return None;

src/ast/expr.rs

@@ -1,9 +1,9 @@
 //! Module defining script expressions.
 
-use super::{ASTFlags, ASTNode, Ident, Stmt, StmtBlock};
+use super::{ASTFlags, ASTNode, Ident, Namespace, Stmt, StmtBlock};
 use crate::engine::{KEYWORD_FN_PTR, OP_EXCLUSIVE_RANGE, OP_INCLUSIVE_RANGE};
 use crate::func::hashing::ALT_ZERO_HASH;
-use crate::tokenizer::Token;
+use crate::tokenizer::{Token, NO_TOKEN};
 use crate::types::dynamic::Union;
 use crate::{
     calc_fn_hash, Dynamic, FnPtr, Identifier, ImmutableString, Position, SmartString, StaticVec,
@@ -197,8 +197,7 @@ impl FnCallHashes {
 #[derive(Clone, Hash)]
 pub struct FnCallExpr {
     /// Namespace of the function, if any.
-    #[cfg(not(feature = "no_module"))]
-    pub namespace: super::Namespace,
+    pub namespace: Namespace,
     /// Function name.
     pub name: ImmutableString,
     /// Pre-calculated hashes.
@@ -208,7 +207,8 @@ pub struct FnCallExpr {
     /// Does this function call capture the parent scope?
     pub capture_parent_scope: bool,
     /// Is this function call a native operator?
-    pub op_token: Option<Token>,
+    /// Otherwise set to [`Token::NONE`].
+    pub op_token: Token,
 }
 
 impl fmt::Debug for FnCallExpr {
@@ -216,15 +216,14 @@ impl fmt::Debug for FnCallExpr {
     #[inline(never)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut ff = f.debug_struct("FnCallExpr");
-        #[cfg(not(feature = "no_module"))]
         if !self.namespace.is_empty() {
             ff.field("namespace", &self.namespace);
         }
         ff.field("hash", &self.hashes)
             .field("name", &self.name)
             .field("args", &self.args);
-        if let Some(ref token) = self.op_token {
-            ff.field("op_token", token);
+        if self.op_token != NO_TOKEN {
+            ff.field("op_token", &self.op_token);
         }
         if self.capture_parent_scope {
             ff.field("capture_parent_scope", &self.capture_parent_scope);
@@ -240,10 +239,7 @@ impl FnCallExpr {
     #[inline(always)]
     #[must_use]
     pub fn is_qualified(&self) -> bool {
-        #[cfg(not(feature = "no_module"))]
-        return !self.namespace.is_empty();
-        #[cfg(feature = "no_module")]
-        return false;
+        !self.namespace.is_empty()
     }
     /// Convert this into an [`Expr::FnCall`].
     #[inline(always)]
@@ -303,9 +299,7 @@ pub enum Expr {
     /// majority of cases (unless there are more than 255 variables defined!).
     /// This is to avoid reading a pointer redirection during each variable access.
     Variable(
-        #[cfg(not(feature = "no_module"))]
-        Box<(Option<NonZeroUsize>, super::Namespace, u64, ImmutableString)>,
-        #[cfg(feature = "no_module")] Box<(Option<NonZeroUsize>, (), u64, ImmutableString)>,
+        Box<(Option<NonZeroUsize>, Namespace, u64, ImmutableString)>,
         Option<NonZeroU8>,
         Position,
     ),
@@ -583,13 +577,12 @@ impl Expr {
 
             Union::FnPtr(f, ..) if !f.is_curried() => Self::FnCall(
                 FnCallExpr {
-                    #[cfg(not(feature = "no_module"))]
-                    namespace: super::Namespace::NONE,
+                    namespace: Namespace::NONE,
                     name: KEYWORD_FN_PTR.into(),
                     hashes: calc_fn_hash(None, f.fn_name(), 1).into(),
                     args: once(Self::StringConstant(f.fn_name().into(), pos)).collect(),
                     capture_parent_scope: false,
-                    op_token: None,
+                    op_token: NO_TOKEN,
                 }
                 .into(),
                 pos,

src/ast/mod.rs

@@ -5,6 +5,7 @@ pub mod expr;
 pub mod flags;
 pub mod ident;
 pub mod namespace;
+pub mod namespace_none;
 pub mod script_fn;
 pub mod stmt;
 
@@ -16,6 +17,8 @@ pub use flags::{ASTFlags, FnAccess};
 pub use ident::Ident;
 #[cfg(not(feature = "no_module"))]
 pub use namespace::Namespace;
+#[cfg(feature = "no_module")]
+pub use namespace_none::Namespace;
 #[cfg(not(feature = "no_module"))]
 #[cfg(not(feature = "no_function"))]
 pub use script_fn::EncapsulatedEnviron;

src/ast/namespace_none.rs

@@ -0,0 +1,22 @@
+//! Namespace reference type.
+#![cfg(feature = "no_module")]
+
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+
+/// _(internals)_ A chain of [module][crate::Module] names to namespace-qualify a variable or function call.
+/// Exported under the `internals` feature only.
+///
+/// Not available under `no_module`.
+#[derive(Debug, Clone, Eq, PartialEq, Default, Hash)]
+pub struct Namespace;
+
+impl Namespace {
+    /// Constant for no namespace.
+    pub const NONE: Self = Self;
+
+    #[inline(always)]
+    pub const fn is_empty(&self) -> bool {
+        true
+    }
+}

src/ast/script_fn.rs

@@ -16,7 +16,6 @@ use std::{fmt, hash::Hash};
 ///
 /// Not available under `no_module` or `no_function`.
 #[cfg(not(feature = "no_module"))]
-#[cfg(not(feature = "no_function"))]
 #[derive(Debug, Clone)]
 pub struct EncapsulatedEnviron {
     /// Functions defined within the same [`AST`][crate::AST].
@@ -24,7 +23,7 @@ pub struct EncapsulatedEnviron {
     /// Imported [modules][crate::Module].
     pub imports: Box<[(ImmutableString, crate::SharedModule)]>,
     /// Globally-defined constants.
-    pub constants: Option<crate::eval::GlobalConstants>,
+    pub constants: Option<crate::eval::SharedGlobalConstants>,
 }
 
 /// _(internals)_ A type containing information on a script-defined function.
@@ -35,7 +34,6 @@ pub struct ScriptFnDef {
     pub body: StmtBlock,
     /// Encapsulated AST environment, if any.
     #[cfg(not(feature = "no_module"))]
-    #[cfg(not(feature = "no_function"))]
     pub environ: Option<crate::Shared<EncapsulatedEnviron>>,
     /// Function name.
     pub name: ImmutableString,
@@ -51,12 +49,14 @@ pub struct ScriptFnDef {
     ///
     /// Block doc-comments are kept in a single string slice with line-breaks within.
     ///
-    /// Line doc-comments are kept in one string slice per line without the termination line-break.
+    /// Line doc-comments are merged, with line-breaks, into a single string slice without a termination line-break.
     ///
     /// Leading white-spaces are stripped, and each string slice always starts with the
     /// corresponding doc-comment leader: `///` or `/**`.
+    ///
+    /// Each line in non-block doc-comments starts with `///`.
     #[cfg(feature = "metadata")]
-    pub comments: Box<[Box<str>]>,
+    pub comments: Box<[crate::Identifier]>,
 }
 
 impl fmt::Display for ScriptFnDef {
@@ -100,10 +100,12 @@ pub struct ScriptFnMetadata<'a> {
     ///
     /// Block doc-comments are kept in a single string slice with line-breaks within.
     ///
-    /// Line doc-comments are kept in one string slice per line without the termination line-break.
+    /// Line doc-comments are merged, with line-breaks, into a single string slice without a termination line-break.
     ///
     /// Leading white-spaces are stripped, and each string slice always starts with the
     /// corresponding doc-comment leader: `///` or `/**`.
+    ///
+    /// Each line in non-block doc-comments starts with `///`.
     #[cfg(feature = "metadata")]
     pub comments: Vec<&'a str>,
 }

src/ast/stmt.rs

@@ -2,7 +2,8 @@
 
 use super::{ASTFlags, ASTNode, BinaryExpr, Expr, FnCallExpr, Ident};
 use crate::engine::KEYWORD_EVAL;
-use crate::tokenizer::{Span, Token};
+use crate::tokenizer::Token;
+use crate::types::Span;
 use crate::{calc_fn_hash, Position, StaticVec, INT};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -61,10 +62,8 @@ impl OpAssignment {
     #[must_use]
     #[inline(always)]
     pub fn new_op_assignment(name: &str, pos: Position) -> Self {
-        Self::new_op_assignment_from_token(
-            &Token::lookup_symbol_from_syntax(name).expect("operator"),
-            pos,
-        )
+        let op = Token::lookup_symbol_from_syntax(name).expect("operator");
+        Self::new_op_assignment_from_token(op, pos)
     }
     /// Create a new [`OpAssignment`] from a [`Token`].
     ///
@@ -72,10 +71,11 @@ impl OpAssignment {
     ///
     /// Panics if the token is not an op-assignment operator.
     #[must_use]
-    pub fn new_op_assignment_from_token(op: &Token, pos: Position) -> Self {
+    pub fn new_op_assignment_from_token(op: Token, pos: Position) -> Self {
         let op_raw = op
             .get_base_op_from_assignment()
             .expect("op-assignment operator");
+
         Self {
             hash_op_assign: calc_fn_hash(None, op.literal_syntax(), 2),
             hash_op: calc_fn_hash(None, op_raw.literal_syntax(), 2),
@@ -92,10 +92,8 @@ impl OpAssignment {
     #[must_use]
     #[inline(always)]
     pub fn new_op_assignment_from_base(name: &str, pos: Position) -> Self {
-        Self::new_op_assignment_from_base_token(
-            &Token::lookup_symbol_from_syntax(name).expect("operator"),
-            pos,
-        )
+        let op = Token::lookup_symbol_from_syntax(name).expect("operator");
+        Self::new_op_assignment_from_base_token(op, pos)
     }
     /// Convert a [`Token`] into a new [`OpAssignment`].
     ///
@@ -104,8 +102,8 @@ impl OpAssignment {
     /// Panics if the token is cannot be converted into an op-assignment operator.
     #[inline(always)]
     #[must_use]
-    pub fn new_op_assignment_from_base_token(op: &Token, pos: Position) -> Self {
-        Self::new_op_assignment_from_token(&op.convert_to_op_assignment().expect("operator"), pos)
+    pub fn new_op_assignment_from_base_token(op: Token, pos: Position) -> Self {
+        Self::new_op_assignment_from_token(op.convert_to_op_assignment().expect("operator"), pos)
     }
 }
 

src/bin/rhai-dbg.rs

@@ -100,19 +100,21 @@ fn print_error(input: &str, mut err: EvalAltResult) {
     // Print error position
     if pos.is_none() {
         // No position
-        println!("{err}");
+        println!("\x1b[31m{err}\x1b[39m");
     } else {
         // Specific position - print line text
         println!("{line_no}{}", lines[pos.line().unwrap() - 1]);
 
+        for (i, err_line) in err.to_string().split('\n').enumerate() {
             // Display position marker
             println!(
-            "{0:>1$} {err}",
-            "^",
-            line_no.len() + pos.position().unwrap(),
+                "\x1b[31m{0:>1$}{err_line}\x1b[39m",
+                if i > 0 { "| " } else { "^ " },
+                line_no.len() + pos.position().unwrap() + 1,
             );
         }
     }
+}
 
 /// Print debug help.
 fn print_debug_help() {
@@ -237,7 +239,13 @@ fn debug_callback(
 ) -> Result<DebuggerCommand, Box<EvalAltResult>> {
     // Check event
     match event {
+        DebuggerEvent::Start if source.is_some() => {
+            println!("\x1b[32m! Script '{}' start\x1b[39m", source.unwrap())
+        }
         DebuggerEvent::Start => println!("\x1b[32m! Script start\x1b[39m"),
+        DebuggerEvent::End if source.is_some() => {
+            println!("\x1b[31m! Script '{}' end\x1b[39m", source.unwrap())
+        }
         DebuggerEvent::End => println!("\x1b[31m! Script end\x1b[39m"),
         DebuggerEvent::Step => (),
         DebuggerEvent::BreakPoint(n) => {
@@ -572,7 +580,7 @@ fn debug_callback(
                     break Err(EvalAltResult::ErrorRuntime(msg.trim().into(), pos).into());
                 }
                 ["run" | "r"] => {
-                    println!("Restarting script...");
+                    println!("Terminating current run...");
                     break Err(EvalAltResult::ErrorTerminated(Dynamic::UNIT, pos).into());
                 }
                 _ => eprintln!(
@@ -604,7 +612,10 @@ fn main() {
     #[allow(deprecated)]
     engine.register_debugger(
         // Store the current source in the debugger state
-        |_| "".into(),
+        |engine, mut debugger| {
+            debugger.set_state(engine.const_empty_string());
+            debugger
+        },
         // Main debugging interface
         move |context, event, node, source, pos| {
             debug_callback(context, event, node, source, pos, &lines)
@@ -627,10 +638,13 @@ fn main() {
     while let Err(err) = engine.run_ast_with_scope(&mut Scope::new(), &ast) {
         match *err {
             // Loop back to restart
-            EvalAltResult::ErrorTerminated(..) => (),
+            EvalAltResult::ErrorTerminated(..) => {
+                println!("Restarting script...");
+            }
             // Break evaluation
             _ => {
                 print_error(&script, *err);
+                println!();
                 break;
             }
         }

src/bin/rhai-repl.rs

@@ -31,14 +31,16 @@ fn print_error(input: &str, mut err: EvalAltResult) {
         // Specific position - print line text
         println!("{line_no}{}", lines[pos.line().unwrap() - 1]);
 
+        for (i, err_line) in err.to_string().split('\n').enumerate() {
             // Display position marker
             println!(
-            "{0:>1$} {err}",
-            "^",
-            line_no.len() + pos.position().unwrap(),
+                "{0:>1$}{err_line}",
+                if i > 0 { "| " } else { "^ " },
+                line_no.len() + pos.position().unwrap() + 1,
             );
         }
     }
+}
 
 /// Print help text.
 fn print_help() {
@@ -245,6 +247,7 @@ fn setup_editor() -> Editor<()> {
     rl
 }
 
+/// Module containing sample functions.
 #[export_module]
 mod sample_functions {
     /// This is a sample function.

src/bin/rhai-run.rs

@@ -8,11 +8,15 @@ fn eprint_error(input: &str, mut err: EvalAltResult) {
         let line_no = format!("{line}: ");
 
         eprintln!("{line_no}{}", lines[line - 1]);
-        eprintln!(
-            "{:>1$} {err_msg}",
-            "^",
-            line_no.len() + pos.position().unwrap(),
+
+        for (i, err_line) in err_msg.to_string().split('\n').enumerate() {
+            // Display position marker
+            println!(
+                "{0:>1$}{err_line}",
+                if i > 0 { "| " } else { "^ " },
+                line_no.len() + pos.position().unwrap() + 1,
             );
+        }
         eprintln!();
     }
 

src/engine.rs

@@ -147,7 +147,7 @@ pub struct Engine {
 
     /// Callback closure for debugging.
     #[cfg(feature = "debugging")]
-    pub(crate) debugger: Option<
+    pub(crate) debugger_interface: Option<
         Box<(
             Box<crate::eval::OnDebuggingInit>,
             Box<crate::eval::OnDebuggerCallback>,
@@ -191,6 +191,9 @@ impl fmt::Debug for Engine {
         #[cfg(not(feature = "unchecked"))]
         f.field("limits", &self.limits);
 
+        #[cfg(feature = "debugging")]
+        f.field("debugger_interface", &self.debugger_interface.is_some());
+
         f.finish()
     }
 }
@@ -305,7 +308,7 @@ impl Engine {
             limits: crate::api::limits::Limits::new(),
 
             #[cfg(feature = "debugging")]
-            debugger: None,
+            debugger_interface: None,
         };
 
         // Add the global namespace module
@@ -348,4 +351,12 @@ impl Engine {
     pub fn const_empty_string(&self) -> ImmutableString {
         self.get_interned_string("")
     }
+
+    /// Is there a debugger interface registered with this [`Engine`]?
+    #[cfg(feature = "debugging")]
+    #[inline(always)]
+    #[must_use]
+    pub(crate) const fn is_debugger_registered(&self) -> bool {
+        self.debugger_interface.is_some()
+    }
 }

src/eval/chaining.rs

@@ -5,8 +5,8 @@ use super::{Caches, GlobalRuntimeState, Target};
 use crate::ast::{ASTFlags, Expr, OpAssignment};
 use crate::config::hashing::SusLock;
 use crate::engine::{FN_IDX_GET, FN_IDX_SET};
+use crate::tokenizer::NO_TOKEN;
 use crate::types::dynamic::Union;
-use crate::types::RestoreOnDrop;
 use crate::{
     calc_fn_hash, Dynamic, Engine, FnArgsVec, Position, RhaiResult, RhaiResultOf, Scope, ERR,
 };
@@ -68,20 +68,12 @@ impl Engine {
         idx: &mut Dynamic,
         pos: Position,
     ) -> RhaiResultOf<Dynamic> {
-        let orig_level = global.level;
-        global.level += 1;
-        let global = &mut *RestoreOnDrop::lock(global, move |g| g.level = orig_level);
+        auto_restore! { let orig_level = global.level; global.level += 1 }
 
-        self.exec_native_fn_call(
-            global,
-            caches,
-            FN_IDX_GET,
-            None,
-            hash_idx().0,
-            &mut [target, idx],
-            true,
-            pos,
-        )
+        let hash = hash_idx().0;
+        let args = &mut [target, idx];
+
+        self.exec_native_fn_call(global, caches, FN_IDX_GET, NO_TOKEN, hash, args, true, pos)
             .map(|(r, ..)| r)
     }
 
@@ -97,19 +89,13 @@ impl Engine {
         is_ref_mut: bool,
         pos: Position,
     ) -> RhaiResultOf<(Dynamic, bool)> {
-        let orig_level = global.level;
-        global.level += 1;
-        let global = &mut *RestoreOnDrop::lock(global, move |g| g.level = orig_level);
+        auto_restore! { let orig_level = global.level; global.level += 1 }
+
+        let hash = hash_idx().1;
+        let args = &mut [target, idx, new_val];
 
         self.exec_native_fn_call(
-            global,
-            caches,
-            FN_IDX_SET,
-            None,
-            hash_idx().1,
-            &mut [target, idx, new_val],
-            is_ref_mut,
-            pos,
+            global, caches, FN_IDX_SET, NO_TOKEN, hash, args, is_ref_mut, pos,
         )
     }
 
@@ -599,7 +585,9 @@ impl Engine {
                             // Try to call index setter if value is changed
                             let idx = &mut idx_val_for_setter;
                             let new_val = &mut new_val;
-                            self.call_indexer_set(
+                            // The return value of a indexer setter (usually `()`) is thrown away and not used.
+                            let _ = self
+                                .call_indexer_set(
                                     global, caches, target, idx, new_val, is_ref_mut, op_pos,
                                 )
                                 .or_else(|e| match *e {
@@ -659,8 +647,8 @@ impl Engine {
 
                             // Try to call index setter
                             let new_val = &mut new_val;
-
-                            self.call_indexer_set(
+                            // The return value of a indexer setter (usually `()`) is thrown away and not used.
+                            let _ = self.call_indexer_set(
                                 global, caches, target, idx_val, new_val, is_ref_mut, op_pos,
                             )?;
                         }
@@ -696,19 +684,17 @@ impl Engine {
                         let reset =
                             self.run_debugger_with_reset(global, caches, scope, this_ptr, rhs)?;
                         #[cfg(feature = "debugging")]
-                        let global =
-                            &mut *RestoreOnDrop::lock_if(reset.is_some(), global, move |g| {
-                                g.debugger_mut().reset_status(reset)
-                            });
+                        auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
                         let crate::ast::FnCallExpr {
                             name, hashes, args, ..
                         } = &**x;
 
                         // Truncate the index values upon exit
+                        auto_restore! {
+                            idx_values => truncate;
                             let offset = idx_values.len() - args.len();
-                        let idx_values =
-                            &mut *RestoreOnDrop::lock(idx_values, move |v| v.truncate(offset));
+                        }
 
                         let call_args = &mut idx_values[offset..];
                         let arg1_pos = args.get(0).map_or(Position::NONE, Expr::position);
@@ -764,9 +750,11 @@ impl Engine {
 
                         if op_info.is_op_assignment() {
                             let args = &mut [target.as_mut()];
+
                             let (mut orig_val, ..) = self
                                 .exec_native_fn_call(
-                                    global, caches, getter, None, *hash_get, args, is_ref_mut, *pos,
+                                    global, caches, getter, NO_TOKEN, *hash_get, args, is_ref_mut,
+                                    *pos,
                                 )
                                 .or_else(|err| match *err {
                                     // Try an indexer if property does not exist
@@ -798,8 +786,9 @@ impl Engine {
                         }
 
                         let args = &mut [target.as_mut(), &mut new_val];
+
                         self.exec_native_fn_call(
-                            global, caches, setter, None, *hash_set, args, is_ref_mut, *pos,
+                            global, caches, setter, NO_TOKEN, *hash_set, args, is_ref_mut, *pos,
                         )
                         .or_else(|err| match *err {
                             // Try an indexer if property does not exist
@@ -824,8 +813,9 @@ impl Engine {
 
                         let ((getter, hash_get), _, name) = &**x;
                         let args = &mut [target.as_mut()];
+
                         self.exec_native_fn_call(
-                            global, caches, getter, None, *hash_get, args, is_ref_mut, *pos,
+                            global, caches, getter, NO_TOKEN, *hash_get, args, is_ref_mut, *pos,
                         )
                         .map_or_else(
                             |err| match *err {
@@ -866,21 +856,17 @@ impl Engine {
                                     global, caches, scope, this_ptr, _node,
                                 )?;
                                 #[cfg(feature = "debugging")]
-                                let global = &mut *RestoreOnDrop::lock_if(
-                                    reset.is_some(),
-                                    global,
-                                    move |g| g.debugger_mut().reset_status(reset),
-                                );
+                                auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
                                 let crate::ast::FnCallExpr {
                                     name, hashes, args, ..
                                 } = &**x;
 
                                 // Truncate the index values upon exit
+                                auto_restore! {
+                                    idx_values => truncate;
                                     let offset = idx_values.len() - args.len();
-                                let idx_values = &mut *RestoreOnDrop::lock(idx_values, move |v| {
-                                    v.truncate(offset)
-                                });
+                                }
 
                                 let call_args = &mut idx_values[offset..];
                                 let arg1_pos = args.get(0).map_or(Position::NONE, Expr::position);
@@ -915,14 +901,13 @@ impl Engine {
                                 self.run_debugger(global, caches, scope, this_ptr, _node)?;
 
                                 let ((getter, hash_get), (setter, hash_set), name) = &**p;
-                                let mut arg_values = [target.as_mut(), &mut Dynamic::UNIT.clone()];
-                                let args = &mut arg_values[..1];
+                                let args = &mut [target.as_mut()];
 
                                 // Assume getters are always pure
                                 let (mut val, ..) = self
                                     .exec_native_fn_call(
-                                        global, caches, getter, None, *hash_get, args, is_ref_mut,
-                                        pos,
+                                        global, caches, getter, NO_TOKEN, *hash_get, args,
+                                        is_ref_mut, pos,
                                     )
                                     .or_else(|err| match *err {
                                         // Try an indexer if property does not exist
@@ -952,14 +937,15 @@ impl Engine {
                                 // Feed the value back via a setter just in case it has been updated
                                 if may_be_changed {
                                     // Re-use args because the first &mut parameter will not be consumed
-                                    let mut arg_values = [target.as_mut(), val.as_mut()];
-                                    let args = &mut arg_values;
-                                    self.exec_native_fn_call(
-                                        global, caches, setter, None, *hash_set, args, is_ref_mut,
-                                        pos,
+                                    let args = &mut [target.as_mut(), val.as_mut()];
+
+                                    // The return value is thrown away and not used.
+                                    let _ = self
+                                        .exec_native_fn_call(
+                                            global, caches, setter, NO_TOKEN, *hash_set, args,
+                                            is_ref_mut, pos,
                                         )
-                                    .or_else(
-                                        |err| match *err {
+                                        .or_else(|err| match *err {
                                             // Try an indexer if property does not exist
                                             ERR::ErrorDotExpr(..) => {
                                                 let idx = &mut name.into();
@@ -978,8 +964,7 @@ impl Engine {
                                                 })
                                             }
                                             _ => Err(err),
-                                        },
-                                    )?;
+                                        })?;
                                 }
 
                                 Ok((result, may_be_changed))
@@ -992,22 +977,17 @@ impl Engine {
                                         global, caches, scope, this_ptr, _node,
                                     )?;
                                     #[cfg(feature = "debugging")]
-                                    let global = &mut *RestoreOnDrop::lock_if(
-                                        reset.is_some(),
-                                        global,
-                                        move |g| g.debugger_mut().reset_status(reset),
-                                    );
+                                    auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
                                     let crate::ast::FnCallExpr {
                                         name, hashes, args, ..
                                     } = &**f;
 
                                     // Truncate the index values upon exit
+                                    auto_restore! {
+                                        idx_values => truncate;
                                         let offset = idx_values.len() - args.len();
-                                    let idx_values =
-                                        &mut *RestoreOnDrop::lock(idx_values, move |v| {
-                                            v.truncate(offset)
-                                        });
+                                    }
 
                                     let call_args = &mut idx_values[offset..];
                                     let pos1 = args.get(0).map_or(Position::NONE, Expr::position);

src/eval/data_check.rs

@@ -74,13 +74,10 @@ impl Engine {
     ///
     /// [`Position`] in [`EvalAltResult`][crate::EvalAltResult] is always [`NONE`][Position::NONE]
     /// and should be set afterwards.
-    pub(crate) fn raise_err_if_over_data_size_limit(
-        &self,
-        (_arr, _map, s): (usize, usize, usize),
-    ) -> RhaiResultOf<()> {
+    pub(crate) fn throw_on_size(&self, (_arr, _map, s): (usize, usize, usize)) -> RhaiResultOf<()> {
         if self
             .limits
-            .max_string_size
+            .max_string_len
             .map_or(false, |max| s > max.get())
         {
             return Err(
@@ -127,9 +124,10 @@ impl Engine {
 
         let sizes = value.borrow().calc_data_sizes(true);
 
-        self.raise_err_if_over_data_size_limit(sizes)
-            .map(|_| value)
-            .map_err(|err| err.fill_position(pos))
+        self.throw_on_size(sizes)
+            .map_err(|err| err.fill_position(pos))?;
+
+        Ok(value)
     }
 
     /// Raise an error if the size of a [`Dynamic`] is out of limits (if any).

src/eval/debugger.rs

@@ -10,10 +10,10 @@ use std::{fmt, iter::repeat, mem};
 
 /// Callback function to initialize the debugger.
 #[cfg(not(feature = "sync"))]
-pub type OnDebuggingInit = dyn Fn(&Engine) -> Dynamic;
+pub type OnDebuggingInit = dyn Fn(&Engine, Debugger) -> Debugger;
 /// Callback function to initialize the debugger.
 #[cfg(feature = "sync")]
-pub type OnDebuggingInit = dyn Fn(&Engine) -> Dynamic + Send + Sync;
+pub type OnDebuggingInit = dyn Fn(&Engine, Debugger) -> Debugger + Send + Sync;
 
 /// Callback function for debugging.
 #[cfg(not(feature = "sync"))]
@@ -268,12 +268,12 @@ impl Debugger {
     /// Create a new [`Debugger`].
     #[inline(always)]
     #[must_use]
-    pub const fn new(status: DebuggerStatus, state: Dynamic) -> Self {
+    pub const fn new(status: DebuggerStatus) -> Self {
         Self {
             status,
             break_points: Vec::new(),
             call_stack: Vec::new(),
-            state,
+            state: Dynamic::UNIT,
         }
     }
     /// Get the current call stack.
@@ -415,7 +415,7 @@ impl Engine {
         this_ptr: &mut Dynamic,
         node: impl Into<ASTNode<'a>>,
     ) -> RhaiResultOf<()> {
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             if let Some(cmd) =
                 self.run_debugger_with_reset_raw(global, caches, scope, this_ptr, node)?
             {
@@ -440,7 +440,7 @@ impl Engine {
         this_ptr: &mut Dynamic,
         node: impl Into<ASTNode<'a>>,
     ) -> RhaiResultOf<Option<DebuggerStatus>> {
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             self.run_debugger_with_reset_raw(global, caches, scope, this_ptr, node)
         } else {
             Ok(None)
@@ -508,11 +508,10 @@ impl Engine {
         node: ASTNode<'a>,
         event: DebuggerEvent,
     ) -> Result<Option<DebuggerStatus>, Box<crate::EvalAltResult>> {
+        if let Some(ref x) = self.debugger_interface {
             let src = global.source_raw().cloned();
             let src = src.as_ref().map(|s| s.as_str());
-        let context = crate::EvalContext::new(self, global, caches, scope, this_ptr);
-
-        if let Some(ref x) = self.debugger {
+            let context = EvalContext::new(self, global, caches, scope, this_ptr);
             let (.., ref on_debugger) = **x;
 
             let command = on_debugger(context, event, node, src, node.position())?;

src/eval/eval_context.rs

@@ -6,7 +6,6 @@ use crate::{Dynamic, Engine, Scope};
 use std::prelude::v1::*;
 
 /// Context of a script evaluation process.
-#[derive(Debug)]
 #[allow(dead_code)]
 pub struct EvalContext<'a, 's, 'ps, 'g, 'c, 't> {
     /// The current [`Engine`].

src/eval/expr.rs

@@ -62,25 +62,22 @@ impl Engine {
             }
             Expr::Variable(v, None, ..) => match &**v {
                 // Normal variable access
-                #[cfg(not(feature = "no_module"))]
                 (_, ns, ..) if ns.is_empty() => {
                     self.search_scope_only(global, caches, scope, this_ptr, expr)
                 }
-                #[cfg(feature = "no_module")]
-                (_, (), ..) => self.search_scope_only(global, caches, scope, this_ptr, expr),
 
                 // Qualified variable access
                 #[cfg(not(feature = "no_module"))]
-                (_, namespace, hash_var, var_name) => {
+                (_, ns, hash_var, var_name) => {
                     // foo:bar::baz::VARIABLE
-                    if let Some(module) = self.search_imports(global, namespace) {
+                    if let Some(module) = self.search_imports(global, ns) {
                         return module.get_qualified_var(*hash_var).map_or_else(
                             || {
                                 let sep = crate::tokenizer::Token::DoubleColon.literal_syntax();
 
                                 Err(ERR::ErrorVariableNotFound(
-                                    format!("{namespace}{sep}{var_name}"),
-                                    namespace.position(),
+                                    format!("{ns}{sep}{var_name}"),
+                                    ns.position(),
                                 )
                                 .into())
                             },
@@ -94,7 +91,7 @@ impl Engine {
 
                     // global::VARIABLE
                     #[cfg(not(feature = "no_function"))]
-                    if namespace.len() == 1 && namespace.root() == crate::engine::KEYWORD_GLOBAL {
+                    if ns.len() == 1 && ns.root() == crate::engine::KEYWORD_GLOBAL {
                         if let Some(ref constants) = global.constants {
                             if let Some(value) =
                                 crate::func::locked_write(constants).get_mut(var_name.as_str())
@@ -109,17 +106,17 @@ impl Engine {
                         let sep = crate::tokenizer::Token::DoubleColon.literal_syntax();
 
                         return Err(ERR::ErrorVariableNotFound(
-                            format!("{namespace}{sep}{var_name}"),
-                            namespace.position(),
+                            format!("{ns}{sep}{var_name}"),
+                            ns.position(),
                         )
                         .into());
                     }
 
-                    Err(
-                        ERR::ErrorModuleNotFound(namespace.to_string(), namespace.position())
-                            .into(),
-                    )
+                    Err(ERR::ErrorModuleNotFound(ns.to_string(), ns.position()).into())
                 }
+
+                #[cfg(feature = "no_module")]
+                _ => unreachable!("Invalid expression {:?}", expr),
             },
             _ => unreachable!("Expr::Variable expected but gets {:?}", expr),
         }
@@ -142,14 +139,18 @@ impl Engine {
 
         let index = match expr {
             // Check if the variable is `this`
-            Expr::Variable(v, None, ..) if v.0.is_none() && v.3 == KEYWORD_THIS => {
+            Expr::Variable(v, None, ..)
+                if v.0.is_none() && v.1.is_empty() && v.3 == KEYWORD_THIS =>
+            {
                 return if this_ptr.is_null() {
                     Err(ERR::ErrorUnboundThis(expr.position()).into())
                 } else {
                     Ok(this_ptr.into())
                 };
             }
+
             _ if global.always_search_scope => 0,
+
             Expr::Variable(_, Some(i), ..) => i.get() as usize,
             // Scripted function with the same name
             #[cfg(not(feature = "no_function"))]
@@ -165,6 +166,7 @@ impl Engine {
                 return Ok(val.into());
             }
             Expr::Variable(v, None, ..) => v.0.map_or(0, NonZeroUsize::get),
+
             _ => unreachable!("Expr::Variable expected but gets {:?}", expr),
         };
 
@@ -232,10 +234,7 @@ impl Engine {
             #[cfg(feature = "debugging")]
             let reset = self.run_debugger_with_reset(global, caches, scope, this_ptr, expr)?;
             #[cfg(feature = "debugging")]
-            let global =
-                &mut *crate::types::RestoreOnDrop::lock_if(reset.is_some(), global, move |g| {
-                    g.debugger_mut().reset_status(reset)
-                });
+            auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
             self.track_operation(global, expr.position())?;
 
@@ -266,10 +265,7 @@ impl Engine {
         #[cfg(feature = "debugging")]
         let reset = self.run_debugger_with_reset(global, caches, scope, this_ptr, expr)?;
         #[cfg(feature = "debugging")]
-        let global =
-            &mut *crate::types::RestoreOnDrop::lock_if(reset.is_some(), global, move |g| {
-                g.debugger_mut().reset_status(reset)
-            });
+        auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
         self.track_operation(global, expr.position())?;
 
@@ -327,7 +323,7 @@ impl Engine {
                                     total_data_sizes.1 + val_sizes.1,
                                     total_data_sizes.2 + val_sizes.2,
                                 );
-                                self.raise_err_if_over_data_size_limit(total_data_sizes)
+                                self.throw_on_size(total_data_sizes)
                                     .map_err(|err| err.fill_position(item_expr.position()))?;
                             }
 
@@ -358,7 +354,7 @@ impl Engine {
                                 total_data_sizes.1 + delta.1,
                                 total_data_sizes.2 + delta.2,
                             );
-                            self.raise_err_if_over_data_size_limit(total_data_sizes)
+                            self.throw_on_size(total_data_sizes)
                                 .map_err(|err| err.fill_position(value_expr.position()))?;
                         }
 

src/eval/global_state.rs

@@ -8,7 +8,7 @@ use std::prelude::v1::*;
 /// Collection of globally-defined constants.
 #[cfg(not(feature = "no_module"))]
 #[cfg(not(feature = "no_function"))]
-pub type GlobalConstants =
+pub type SharedGlobalConstants =
     crate::Shared<crate::Locked<std::collections::BTreeMap<ImmutableString, Dynamic>>>;
 
 /// _(internals)_ Global runtime states.
@@ -67,12 +67,12 @@ pub struct GlobalRuntimeState {
     /// Interior mutability is needed because it is shared in order to aid in cloning.
     #[cfg(not(feature = "no_module"))]
     #[cfg(not(feature = "no_function"))]
-    pub constants: Option<GlobalConstants>,
+    pub constants: Option<SharedGlobalConstants>,
     /// Custom state that can be used by the external host.
     pub tag: Dynamic,
     /// Debugging interface.
     #[cfg(feature = "debugging")]
-    pub(crate) debugger: Option<super::Debugger>,
+    pub(crate) debugger: Option<Box<super::Debugger>>,
 }
 
 impl GlobalRuntimeState {
@@ -103,8 +103,9 @@ impl GlobalRuntimeState {
             tag: engine.default_tag().clone(),
 
             #[cfg(feature = "debugging")]
-            debugger: engine.debugger.as_ref().map(|x| {
-                crate::eval::Debugger::new(crate::eval::DebuggerStatus::Init, (x.0)(engine))
+            debugger: engine.debugger_interface.as_ref().map(|x| {
+                let dbg = crate::eval::Debugger::new(crate::eval::DebuggerStatus::Init);
+                (x.0)(engine, dbg).into()
             }),
         }
     }
@@ -115,7 +116,7 @@ impl GlobalRuntimeState {
     #[inline]
     #[must_use]
     pub fn num_imports(&self) -> usize {
-        self.modules.as_ref().map_or(0, |m| m.len())
+        self.modules.as_deref().map_or(0, crate::StaticVec::len)
     }
     /// Get the globally-imported [module][crate::Module] at a particular index.
     ///
@@ -138,7 +139,7 @@ impl GlobalRuntimeState {
         &mut self,
         index: usize,
     ) -> Option<&mut crate::SharedModule> {
-        self.modules.as_mut().and_then(|m| m.get_mut(index))
+        self.modules.as_deref_mut().and_then(|m| m.get_mut(index))
     }
     /// Get the index of a globally-imported [module][crate::Module] by name.
     ///
@@ -183,8 +184,8 @@ impl GlobalRuntimeState {
             self.imports = None;
             self.modules = None;
         } else if self.imports.is_some() {
-            self.imports.as_mut().unwrap().truncate(size);
-            self.modules.as_mut().unwrap().truncate(size);
+            self.imports.as_deref_mut().unwrap().truncate(size);
+            self.modules.as_deref_mut().unwrap().truncate(size);
         }
     }
     /// Get an iterator to the stack of globally-imported [modules][crate::Module] in reverse order.
@@ -194,10 +195,11 @@ impl GlobalRuntimeState {
     #[inline]
     pub fn iter_imports(&self) -> impl Iterator<Item = (&str, &crate::Module)> {
         self.imports
-            .iter()
-            .flat_map(|x| x.iter())
+            .as_deref()
+            .into_iter()
+            .flatten()
             .rev()
-            .zip(self.modules.iter().flat_map(|x| x.iter()).rev())
+            .zip(self.modules.as_deref().into_iter().flatten().rev())
             .map(|(name, module)| (name.as_str(), &**module))
     }
     /// Get an iterator to the stack of globally-imported [modules][crate::Module] in reverse order.
@@ -209,10 +211,11 @@ impl GlobalRuntimeState {
         &self,
     ) -> impl Iterator<Item = (&ImmutableString, &crate::SharedModule)> {
         self.imports
-            .iter()
-            .flat_map(|x| x.iter())
+            .as_deref()
+            .into_iter()
+            .flatten()
             .rev()
-            .zip(self.modules.iter().flat_map(|x| x.iter()).rev())
+            .zip(self.modules.as_deref().into_iter().flatten())
     }
     /// Get an iterator to the stack of globally-imported [modules][crate::Module] in forward order.
     ///
@@ -223,9 +226,10 @@ impl GlobalRuntimeState {
         &self,
     ) -> impl Iterator<Item = (&ImmutableString, &crate::SharedModule)> {
         self.imports
-            .iter()
-            .flat_map(|x| x.iter())
-            .zip(self.modules.iter().flat_map(|x| x.iter()))
+            .as_deref()
+            .into_iter()
+            .flatten()
+            .zip(self.modules.as_deref().into_iter().flatten())
     }
     /// Can the particular function with [`Dynamic`] parameter(s) exist in the stack of
     /// globally-imported [modules][crate::Module]?
@@ -234,7 +238,7 @@ impl GlobalRuntimeState {
     #[cfg(not(feature = "no_module"))]
     #[inline]
     pub(crate) fn may_contain_dynamic_fn(&self, hash_script: u64) -> bool {
-        self.modules.as_ref().map_or(false, |m| {
+        self.modules.as_deref().map_or(false, |m| {
             m.iter().any(|m| m.may_contain_dynamic_fn(hash_script))
         })
     }
@@ -323,7 +327,7 @@ impl GlobalRuntimeState {
     /// Panics if the debugging interface is not set.
     #[cfg(feature = "debugging")]
     pub fn debugger_mut(&mut self) -> &mut super::Debugger {
-        self.debugger.as_mut().unwrap()
+        self.debugger.as_deref_mut().unwrap()
     }
 }
 

src/eval/mod.rs

@@ -17,10 +17,10 @@ pub use debugger::{
     OnDebuggerCallback, OnDebuggingInit,
 };
 pub use eval_context::EvalContext;
+pub use global_state::GlobalRuntimeState;
 #[cfg(not(feature = "no_module"))]
 #[cfg(not(feature = "no_function"))]
-pub use global_state::GlobalConstants;
-pub use global_state::GlobalRuntimeState;
+pub use global_state::SharedGlobalConstants;
 #[cfg(not(feature = "no_index"))]
 pub use target::calc_offset_len;
 pub use target::{calc_index, Target};

src/eval/stmt.rs

@@ -3,16 +3,28 @@
 use super::{Caches, EvalContext, GlobalRuntimeState, Target};
 use crate::api::events::VarDefInfo;
 use crate::ast::{
-    ASTFlags, BinaryExpr, Expr, Ident, OpAssignment, Stmt, SwitchCasesCollection, TryCatchBlock,
+    ASTFlags, BinaryExpr, Expr, OpAssignment, Stmt, SwitchCasesCollection, TryCatchBlock,
 };
 use crate::func::{get_builtin_op_assignment_fn, get_hasher};
-use crate::types::dynamic::AccessMode;
-use crate::types::RestoreOnDrop;
+use crate::types::dynamic::{AccessMode, Union};
 use crate::{Dynamic, Engine, RhaiResult, RhaiResultOf, Scope, ERR, INT};
 use std::hash::{Hash, Hasher};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
+impl Dynamic {
+    /// If the value is a string, intern it.
+    #[inline(always)]
+    fn intern_string(self, engine: &Engine) -> Self {
+        match self.0 {
+            Union::Str(..) => engine
+                .get_interned_string(self.into_immutable_string().expect("`ImmutableString`"))
+                .into(),
+            _ => self,
+        }
+    }
+}
+
 impl Engine {
     /// Evaluate a statements block.
     pub(crate) fn eval_stmt_block(
@@ -29,10 +41,10 @@ impl Engine {
         }
 
         // Restore scope at end of block if necessary
+        auto_restore! {
+            scope if restore_orig_state => rewind;
             let orig_scope_len = scope.len();
-        let scope = &mut *RestoreOnDrop::lock_if(restore_orig_state, scope, move |s| {
-            s.rewind(orig_scope_len);
-        });
+        }
 
         // Restore global state at end of block if necessary
         let orig_always_search_scope = global.always_search_scope;
@@ -43,7 +55,7 @@ impl Engine {
             global.scope_level += 1;
         }
 
-        let global = &mut *RestoreOnDrop::lock_if(restore_orig_state, global, move |g| {
+        auto_restore!(global if restore_orig_state => move |g| {
             g.scope_level -= 1;
 
             #[cfg(not(feature = "no_module"))]
@@ -55,10 +67,10 @@ impl Engine {
         });
 
         // Pop new function resolution caches at end of block
+        auto_restore! {
+            caches => rewind_fn_resolution_caches;
             let orig_fn_resolution_caches_len = caches.fn_resolution_caches_len();
-        let caches = &mut *RestoreOnDrop::lock(caches, move |c| {
-            c.rewind_fn_resolution_caches(orig_fn_resolution_caches_len)
-        });
+        }
 
         // Run the statements
         statements.iter().try_fold(Dynamic::UNIT, |_, stmt| {
@@ -129,23 +141,25 @@ impl Engine {
             let args = &mut [&mut *lock_guard, &mut new_val];
 
             if self.fast_operators() {
-                if let Some(func) = get_builtin_op_assignment_fn(op_assign_token, args[0], args[1])
+                if let Some((func, ctx)) =
+                    get_builtin_op_assignment_fn(op_assign_token.clone(), args[0], args[1])
                 {
                     // Built-in found
                     let op = op_assign_token.literal_syntax();
+                    auto_restore! { let orig_level = global.level; global.level += 1 }
 
-                    let orig_level = global.level;
-                    global.level += 1;
-                    let global = &*RestoreOnDrop::lock(global, move |g| g.level = orig_level);
-
-                    let context = (self, op, None, global, *op_pos).into();
+                    let context = if ctx {
+                        Some((self, op, None, &*global, *op_pos).into())
+                    } else {
+                        None
+                    };
                     return func(context, args).map(|_| ());
                 }
             }
 
             let op_assign = op_assign_token.literal_syntax();
             let op = op_token.literal_syntax();
-            let token = Some(op_assign_token);
+            let token = op_assign_token.clone();
 
             match self
                 .exec_native_fn_call(global, caches, op_assign, token, hash, args, true, *op_pos)
@@ -154,7 +168,7 @@ impl Engine {
                 Err(err) if matches!(*err, ERR::ErrorFunctionNotFound(ref f, ..) if f.starts_with(op_assign)) =>
                 {
                     // Expand to `var = var op rhs`
-                    let token = Some(op_token);
+                    let token = op_token.clone();
 
                     *args[0] = self
                         .exec_native_fn_call(
@@ -168,14 +182,14 @@ impl Engine {
             self.check_data_size(&*args[0], root.position())?;
         } else {
             // Normal assignment
-
-            // If value is a string, intern it
-            if new_val.is_string() {
-                let value = new_val.into_immutable_string().expect("`ImmutableString`");
-                new_val = self.get_interned_string(value).into();
+            match target {
+                // Lock it again just in case it is shared
+                Target::RefMut(_) | Target::TempValue(_) => {
+                    *target.write_lock::<Dynamic>().unwrap() = new_val
+                }
+                #[allow(unreachable_patterns)]
+                _ => **target = new_val,
             }
-
-            *target.write_lock::<Dynamic>().unwrap() = new_val;
         }
 
         target.propagate_changed_value(op_info.pos)
@@ -194,9 +208,7 @@ impl Engine {
         #[cfg(feature = "debugging")]
         let reset = self.run_debugger_with_reset(global, caches, scope, this_ptr, stmt)?;
         #[cfg(feature = "debugging")]
-        let global = &mut *RestoreOnDrop::lock_if(reset.is_some(), global, move |g| {
-            g.debugger_mut().reset_status(reset)
-        });
+        auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
         // Coded this way for better branch prediction.
         // Popular branches are lifted out of the `match` statement into their own branches.
@@ -223,14 +235,13 @@ impl Engine {
 
                 let mut target = self.search_namespace(global, caches, scope, this_ptr, lhs)?;
 
+                let is_temp_result = !target.is_ref();
                 let var_name = x.3.as_str();
 
                 #[cfg(not(feature = "no_closure"))]
                 // Also handle case where target is a `Dynamic` shared value
                 // (returned by a variable resolver, for example)
-                let is_temp_result = !target.is_ref() && !target.is_shared();
-                #[cfg(feature = "no_closure")]
-                let is_temp_result = !target.is_ref();
+                let is_temp_result = is_temp_result && !target.is_shared();
 
                 // Cannot assign to temp result from expression
                 if is_temp_result {
@@ -250,19 +261,16 @@ impl Engine {
 
             #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
             {
-                let mut rhs_val = self
+                let rhs_val = self
                     .eval_expr(global, caches, scope, this_ptr, rhs)?
-                    .flatten();
-
-                // If value is a string, intern it
-                if rhs_val.is_string() {
-                    let value = rhs_val.into_immutable_string().expect("`ImmutableString`");
-                    rhs_val = self.get_interned_string(value).into();
-                }
+                    .flatten()
+                    .intern_string(self);
 
                 let _new_val = Some((rhs_val, op_info));
 
-                // Must be either `var[index] op= val` or `var.prop op= val`
+                // Must be either `var[index] op= val` or `var.prop op= val`.
+                // The return value of any op-assignment (should be `()`) is thrown away and not used.
+                let _ =
                     match lhs {
                         // name op= rhs (handled above)
                         Expr::Variable(..) => {
@@ -270,14 +278,12 @@ impl Engine {
                         }
                         // idx_lhs[idx_expr] op= rhs
                         #[cfg(not(feature = "no_index"))]
-                    Expr::Index(..) => {
-                        self.eval_dot_index_chain(global, caches, scope, this_ptr, lhs, _new_val)
-                    }
+                        Expr::Index(..) => self
+                            .eval_dot_index_chain(global, caches, scope, this_ptr, lhs, _new_val),
                         // dot_lhs.dot_rhs op= rhs
                         #[cfg(not(feature = "no_object"))]
-                    Expr::Dot(..) => {
-                        self.eval_dot_index_chain(global, caches, scope, this_ptr, lhs, _new_val)
-                    }
+                        Expr::Dot(..) => self
+                            .eval_dot_index_chain(global, caches, scope, this_ptr, lhs, _new_val),
                         _ => unreachable!("cannot assign to expression: {:?}", lhs),
                     }?;
 
@@ -494,27 +500,29 @@ impl Engine {
                 // 2) Global modules - packages
                 // 3) Imported modules - functions marked with global namespace
                 // 4) Global sub-modules - functions marked with global namespace
-                let func = self
+                let iter_func = self
                     .global_modules
                     .iter()
                     .find_map(|m| m.get_iter(iter_type));
 
                 #[cfg(not(feature = "no_module"))]
-                let func = func.or_else(|| global.get_iter(iter_type)).or_else(|| {
+                let iter_func = iter_func
+                    .or_else(|| global.get_iter(iter_type))
+                    .or_else(|| {
                         self.global_sub_modules
-                        .iter()
-                        .flat_map(|m| m.values())
-                        .find_map(|m| m.get_qualified_iter(iter_type))
+                            .as_deref()
+                            .into_iter()
+                            .flatten()
+                            .find_map(|(_, m)| m.get_qualified_iter(iter_type))
                     });
 
-                let func = func.ok_or_else(|| ERR::ErrorFor(expr.start_position()))?;
+                let iter_func = iter_func.ok_or_else(|| ERR::ErrorFor(expr.start_position()))?;
 
                 // Restore scope at end of statement
+                auto_restore! {
+                    scope => rewind;
                     let orig_scope_len = scope.len();
-                let scope = &mut *RestoreOnDrop::lock(scope, move |s| {
-                    s.rewind(orig_scope_len);
-                });
-
+                }
                 // Add the loop variables
                 let counter_index = if counter.is_empty() {
                     usize::MAX
@@ -528,7 +536,7 @@ impl Engine {
 
                 let mut result = Dynamic::UNIT;
 
-                for (x, iter_value) in func(iter_obj).enumerate() {
+                for (x, iter_value) in iter_func(iter_obj).enumerate() {
                     // Increment counter
                     if counter_index < usize::MAX {
                         // As the variable increments from 0, this should always work
@@ -596,10 +604,7 @@ impl Engine {
             Stmt::TryCatch(x, ..) => {
                 let TryCatchBlock {
                     try_block,
-                    catch_var:
-                        Ident {
-                            name: catch_var, ..
-                        },
+                    catch_var,
                     catch_block,
                 } = &**x;
 
@@ -644,14 +649,13 @@ impl Engine {
                         };
 
                         // Restore scope at end of block
+                        auto_restore! {
+                            scope if !catch_var.is_empty() => rewind;
                             let orig_scope_len = scope.len();
-                        let scope =
-                            &mut *RestoreOnDrop::lock_if(!catch_var.is_empty(), scope, move |s| {
-                                s.rewind(orig_scope_len);
-                            });
+                        }
 
                         if !catch_var.is_empty() {
-                            scope.push(catch_var.clone(), err_value);
+                            scope.push(catch_var.name.clone(), err_value);
                         }
 
                         self.eval_stmt_block(global, caches, scope, this_ptr, catch_block, true)
@@ -721,7 +725,8 @@ impl Engine {
                 // Evaluate initial value
                 let mut value = self
                     .eval_expr(global, caches, scope, this_ptr, expr)?
-                    .flatten();
+                    .flatten()
+                    .intern_string(self);
 
                 let _alias = if !rewind_scope {
                     // Put global constants into global module
@@ -759,7 +764,7 @@ impl Engine {
 
                 #[cfg(not(feature = "no_module"))]
                 if let Some(alias) = _alias {
-                    scope.add_alias_by_index(scope.len() - 1, alias.name.as_str().into());
+                    scope.add_alias_by_index(scope.len() - 1, alias.as_str().into());
                 }
 
                 Ok(Dynamic::UNIT)
@@ -826,6 +831,7 @@ impl Engine {
             // Export statement
             #[cfg(not(feature = "no_module"))]
             Stmt::Export(x, ..) => {
+                use crate::ast::Ident;
                 let (Ident { name, pos, .. }, Ident { name: alias, .. }) = &**x;
                 // Mark scope variables as public
                 scope.search(name).map_or_else(

src/eval/target.rs

@@ -81,6 +81,7 @@ pub fn calc_index<E>(
 
 /// A type that encapsulates a mutation target for an expression with side effects.
 #[derive(Debug)]
+#[must_use]
 pub enum Target<'a> {
     /// The target is a mutable reference to a [`Dynamic`].
     RefMut(&'a mut Dynamic),
@@ -88,9 +89,9 @@ pub enum Target<'a> {
     #[cfg(not(feature = "no_closure"))]
     SharedValue {
         /// Lock guard to the shared [`Dynamic`].
-        source: crate::types::dynamic::DynamicWriteLock<'a, Dynamic>,
-        /// Copy of the value.
-        value: Dynamic,
+        guard: crate::types::dynamic::DynamicWriteLock<'a, Dynamic>,
+        /// Copy of the shared value.
+        shared_value: Dynamic,
     },
     /// The target is a temporary [`Dynamic`] value (i.e. its mutation can cause no side effects).
     TempValue(Dynamic),
@@ -177,13 +178,12 @@ impl<'a> Target<'a> {
         }
     }
     /// Is the [`Target`] a shared value?
-    #[cfg(not(feature = "no_closure"))]
     #[inline]
     #[must_use]
     pub fn is_shared(&self) -> bool {
-        match self {
-            Self::RefMut(r) => r.is_shared(),
         #[cfg(not(feature = "no_closure"))]
+        return match self {
+            Self::RefMut(r) => r.is_shared(),
             Self::SharedValue { .. } => true,
             Self::TempValue(value) => value.is_shared(),
             #[cfg(not(feature = "no_index"))]
@@ -191,16 +191,17 @@ impl<'a> Target<'a> {
             | Self::BitField { .. }
             | Self::BlobByte { .. }
             | Self::StringChar { .. } => false,
-        }
+        };
+        #[cfg(feature = "no_closure")]
+        return false;
     }
     /// Get the value of the [`Target`] as a [`Dynamic`], cloning a referenced value if necessary.
     #[inline]
-    #[must_use]
     pub fn take_or_clone(self) -> Dynamic {
         match self {
             Self::RefMut(r) => r.clone(), // Referenced value is cloned
             #[cfg(not(feature = "no_closure"))]
-            Self::SharedValue { value, .. } => value, // Original shared value is simply taken
+            Self::SharedValue { shared_value, .. } => shared_value, // Original shared value is simply taken
             Self::TempValue(value) => value, // Owned value is simply taken
             #[cfg(not(feature = "no_index"))]
             Self::Bit { value, .. } => value, // boolean is taken
@@ -223,12 +224,11 @@ impl<'a> Target<'a> {
     }
     /// Convert a shared or reference [`Target`] into a target with an owned value.
     #[inline(always)]
-    #[must_use]
     pub fn into_owned(self) -> Self {
         match self {
             Self::RefMut(r) => Self::TempValue(r.clone()),
             #[cfg(not(feature = "no_closure"))]
-            Self::SharedValue { value, .. } => Self::TempValue(value),
+            Self::SharedValue { shared_value, .. } => Self::TempValue(shared_value),
             _ => self,
         }
     }
@@ -240,7 +240,7 @@ impl<'a> Target<'a> {
         match self {
             Self::RefMut(r) => r,
             #[cfg(not(feature = "no_closure"))]
-            Self::SharedValue { source, .. } => source,
+            Self::SharedValue { guard, .. } => guard,
             Self::TempValue(value) => value,
             #[cfg(not(feature = "no_index"))]
             Self::Bit { source, .. } => source,
@@ -366,9 +366,12 @@ impl<'a> From<&'a mut Dynamic> for Target<'a> {
         #[cfg(not(feature = "no_closure"))]
         if value.is_shared() {
             // Cloning is cheap for a shared value
-            let val = value.clone();
-            let source = value.write_lock::<Dynamic>().expect("`Dynamic`");
-            return Self::SharedValue { source, value: val };
+            let shared_value = value.clone();
+            let guard = value.write_lock::<Dynamic>().expect("`Dynamic`");
+            return Self::SharedValue {
+                guard,
+                shared_value,
+            };
         }
 
         Self::RefMut(value)
@@ -383,7 +386,7 @@ impl Deref for Target<'_> {
         match self {
             Self::RefMut(r) => r,
             #[cfg(not(feature = "no_closure"))]
-            Self::SharedValue { source, .. } => source,
+            Self::SharedValue { guard, .. } => guard,
             Self::TempValue(ref value) => value,
             #[cfg(not(feature = "no_index"))]
             Self::Bit { ref value, .. }
@@ -416,7 +419,7 @@ impl DerefMut for Target<'_> {
         match self {
             Self::RefMut(r) => r,
             #[cfg(not(feature = "no_closure"))]
-            Self::SharedValue { source, .. } => &mut *source,
+            Self::SharedValue { guard, .. } => &mut *guard,
             Self::TempValue(ref mut value) => value,
             #[cfg(not(feature = "no_index"))]
             Self::Bit { ref mut value, .. }
@@ -437,7 +440,6 @@ impl AsMut<Dynamic> for Target<'_> {
 
 impl<T: Into<Dynamic>> From<T> for Target<'_> {
     #[inline(always)]
-    #[must_use]
     fn from(value: T) -> Self {
         Self::TempValue(value.into())
     }

src/func/builtin.rs

@@ -24,8 +24,8 @@ use num_traits::Float;
 #[cfg(feature = "decimal")]
 use rust_decimal::Decimal;
 
-/// The message: data type was checked
-const BUILTIN: &str = "data type was checked";
+/// The `unchecked` feature is not active.
+const CHECKED_BUILD: bool = cfg!(not(feature = "unchecked"));
 
 /// Is the type a numeric type?
 #[inline]
@@ -71,12 +71,12 @@ fn is_numeric(type_id: TypeId) -> bool {
 
 /// A function that returns `true`.
 #[inline(always)]
-fn const_true_fn(_: NativeCallContext, _: &mut [&mut Dynamic]) -> RhaiResult {
+fn const_true_fn(_: Option<NativeCallContext>, _: &mut [&mut Dynamic]) -> RhaiResult {
     Ok(Dynamic::TRUE)
 }
 /// A function that returns `false`.
 #[inline(always)]
-fn const_false_fn(_: NativeCallContext, _: &mut [&mut Dynamic]) -> RhaiResult {
+fn const_false_fn(_: Option<NativeCallContext>, _: &mut [&mut Dynamic]) -> RhaiResult {
     Ok(Dynamic::FALSE)
 }
 
@@ -84,60 +84,60 @@ fn const_false_fn(_: NativeCallContext, _: &mut [&mut Dynamic]) -> RhaiResult {
 ///
 /// The return function will be registered as a _method_, so the first parameter cannot be consumed.
 #[must_use]
-pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<FnBuiltin> {
+pub fn get_builtin_binary_op_fn(op: Token, x: &Dynamic, y: &Dynamic) -> Option<FnBuiltin> {
     let type1 = x.type_id();
     let type2 = y.type_id();
 
     macro_rules! impl_op {
-        ($xx:ident $op:tt $yy:ident) => { |_, args| {
-            let x = &*args[0].read_lock::<$xx>().expect(BUILTIN);
-            let y = &*args[1].read_lock::<$yy>().expect(BUILTIN);
+        ($xx:ident $op:tt $yy:ident) => { (|_, args| {
+            let x = &*args[0].read_lock::<$xx>().unwrap();
+            let y = &*args[1].read_lock::<$yy>().unwrap();
             Ok((x $op y).into())
-        } };
-        ($xx:ident . $func:ident ( $yy:ty )) => { |_, args| {
-            let x = &*args[0].read_lock::<$xx>().expect(BUILTIN);
-            let y = &*args[1].read_lock::<$yy>().expect(BUILTIN);
+        }, false) };
+        ($xx:ident . $func:ident ( $yy:ty )) => { (|_, args| {
+            let x = &*args[0].read_lock::<$xx>().unwrap();
+            let y = &*args[1].read_lock::<$yy>().unwrap();
             Ok(x.$func(y).into())
-        } };
-        ($xx:ident . $func:ident ( $yy:ident . $yyy:ident () )) => { |_, args| {
-            let x = &*args[0].read_lock::<$xx>().expect(BUILTIN);
-            let y = &*args[1].read_lock::<$yy>().expect(BUILTIN);
+        }, false) };
+        ($xx:ident . $func:ident ( $yy:ident . $yyy:ident () )) => { (|_, args| {
+            let x = &*args[0].read_lock::<$xx>().unwrap();
+            let y = &*args[1].read_lock::<$yy>().unwrap();
             Ok(x.$func(y.$yyy()).into())
-        } };
-        ($func:ident ( $op:tt )) => { |_, args| {
+        }, false) };
+        ($func:ident ( $op:tt )) => { (|_, args| {
             let (x, y) = $func(args);
             Ok((x $op y).into())
-        } };
-        ($base:ty => $xx:ident $op:tt $yy:ident) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN) as $base;
-            let y = args[1].$yy().expect(BUILTIN) as $base;
+        }, false) };
+        ($base:ty => $xx:ident $op:tt $yy:ident) => { (|_, args| {
+            let x = args[0].$xx().unwrap() as $base;
+            let y = args[1].$yy().unwrap() as $base;
             Ok((x $op y).into())
-        } };
-        ($base:ty => $xx:ident . $func:ident ( $yy:ident as $yyy:ty)) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN) as $base;
-            let y = args[1].$yy().expect(BUILTIN) as $base;
+        }, false) };
+        ($base:ty => $xx:ident . $func:ident ( $yy:ident as $yyy:ty)) => { (|_, args| {
+            let x = args[0].$xx().unwrap() as $base;
+            let y = args[1].$yy().unwrap() as $base;
             Ok(x.$func(y as $yyy).into())
-        } };
-        ($base:ty => $func:ident ( $xx:ident, $yy:ident )) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN) as $base;
-            let y = args[1].$yy().expect(BUILTIN) as $base;
+        }, false) };
+        ($base:ty => $func:ident ( $xx:ident, $yy:ident )) => { (|_, args| {
+            let x = args[0].$xx().unwrap() as $base;
+            let y = args[1].$yy().unwrap() as $base;
             $func(x, y).map(Into::into)
-        } };
-        (from $base:ty => $xx:ident $op:tt $yy:ident) => { |_, args| {
-            let x = <$base>::from(args[0].$xx().expect(BUILTIN));
-            let y = <$base>::from(args[1].$yy().expect(BUILTIN));
+        }, false) };
+        (from $base:ty => $xx:ident $op:tt $yy:ident) => { (|_, args| {
+            let x = <$base>::from(args[0].$xx().unwrap());
+            let y = <$base>::from(args[1].$yy().unwrap());
             Ok((x $op y).into())
-        } };
-        (from $base:ty => $xx:ident . $func:ident ( $yy:ident )) => { |_, args| {
-            let x = <$base>::from(args[0].$xx().expect(BUILTIN));
-            let y = <$base>::from(args[1].$yy().expect(BUILTIN));
+        }, false) };
+        (from $base:ty => $xx:ident . $func:ident ( $yy:ident )) => { (|_, args| {
+            let x = <$base>::from(args[0].$xx().unwrap());
+            let y = <$base>::from(args[1].$yy().unwrap());
             Ok(x.$func(y).into())
-        } };
-        (from $base:ty => $func:ident ( $xx:ident, $yy:ident )) => { |_, args| {
-            let x = <$base>::from(args[0].$xx().expect(BUILTIN));
-            let y = <$base>::from(args[1].$yy().expect(BUILTIN));
+        }, false) };
+        (from $base:ty => $func:ident ( $xx:ident, $yy:ident )) => { (|_, args| {
+            let x = <$base>::from(args[0].$xx().unwrap());
+            let y = <$base>::from(args[1].$yy().unwrap());
             $func(x, y).map(Into::into)
-        } };
+        }, false) };
     }
 
     // Check for common patterns
@@ -183,16 +183,8 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
                 Ampersand => Some(impl_op!(INT => as_int & as_int)),
                 Pipe => Some(impl_op!(INT => as_int | as_int)),
                 XOr => Some(impl_op!(INT => as_int ^ as_int)),
-                ExclusiveRange => Some(|_, args| {
-                    let x = args[0].as_int().expect(BUILTIN);
-                    let y = args[1].as_int().expect(BUILTIN);
-                    Ok((x..y).into())
-                }),
-                InclusiveRange => Some(|_, args| {
-                    let x = args[0].as_int().expect(BUILTIN);
-                    let y = args[1].as_int().expect(BUILTIN);
-                    Ok((x..=y).into())
-                }),
+                ExclusiveRange => Some(impl_op!(INT => as_int .. as_int)),
+                InclusiveRange => Some(impl_op!(INT => as_int ..= as_int)),
                 _ => None,
             };
         }
@@ -214,19 +206,20 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
 
         if type1 == TypeId::of::<ImmutableString>() {
             return match op {
-                Plus => Some(|_ctx, args| {
-                    let s1 = &*args[0].read_lock::<ImmutableString>().expect(BUILTIN);
-                    let s2 = &*args[1].read_lock::<ImmutableString>().expect(BUILTIN);
+                Plus => Some((
+                    |_ctx, args| {
+                        let s1 = &*args[0].read_lock::<ImmutableString>().unwrap();
+                        let s2 = &*args[1].read_lock::<ImmutableString>().unwrap();
 
                         #[cfg(not(feature = "unchecked"))]
-                    if !s1.is_empty() && !s2.is_empty() {
-                        let total_len = s1.len() + s2.len();
-                        _ctx.engine()
-                            .raise_err_if_over_data_size_limit((0, 0, total_len))?;
-                    }
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((0, 0, s1.len() + s2.len()))?;
 
                         Ok((s1 + s2).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 Minus => Some(impl_op!(ImmutableString - ImmutableString)),
                 EqualsTo => Some(impl_op!(ImmutableString == ImmutableString)),
                 NotEqualsTo => Some(impl_op!(ImmutableString != ImmutableString)),
@@ -240,20 +233,22 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
 
         if type1 == TypeId::of::<char>() {
             return match op {
-                Plus => Some(|_ctx, args| {
-                    let x = args[0].as_char().expect(BUILTIN);
-                    let y = args[1].as_char().expect(BUILTIN);
+                Plus => Some((
+                    |_ctx, args| {
+                        let x = args[0].as_char().unwrap();
+                        let y = args[1].as_char().unwrap();
 
                         let mut result = SmartString::new_const();
                         result.push(x);
                         result.push(y);
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine()
-                        .raise_err_if_over_data_size_limit((0, 0, result.len()))?;
+                        _ctx.unwrap().engine().throw_on_size((0, 0, result.len()))?;
 
                         Ok(result.into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 EqualsTo => Some(impl_op!(char => as_char == as_char)),
                 NotEqualsTo => Some(impl_op!(char => as_char != as_char)),
                 GreaterThan => Some(impl_op!(char => as_char > as_char)),
@@ -269,27 +264,28 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
             use crate::Blob;
 
             return match op {
-                Plus => Some(|_ctx, args| {
-                    let blob1 = &*args[0].read_lock::<Blob>().expect(BUILTIN);
-                    let blob2 = &*args[1].read_lock::<Blob>().expect(BUILTIN);
+                Plus => Some((
+                    |_ctx, args| {
+                        let b2 = &*args[1].read_lock::<Blob>().unwrap();
+                        if b2.is_empty() {
+                            return Ok(args[0].flatten_clone());
+                        }
+                        let b1 = &*args[0].read_lock::<Blob>().unwrap();
+                        if b1.is_empty() {
+                            return Ok(args[1].flatten_clone());
+                        }
 
-                    Ok(Dynamic::from_blob(if blob2.is_empty() {
-                        blob1.clone()
-                    } else if blob1.is_empty() {
-                        blob2.clone()
-                    } else {
                         #[cfg(not(feature = "unchecked"))]
-                        _ctx.engine().raise_err_if_over_data_size_limit((
-                            blob1.len() + blob2.len(),
-                            0,
-                            0,
-                        ))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((b1.len() + b2.len(), 0, 0))?;
 
-                        let mut blob = blob1.clone();
-                        blob.extend(blob2);
-                        blob
-                    }))
-                }),
+                        let mut blob = b1.clone();
+                        blob.extend(b2);
+                        Ok(Dynamic::from_blob(blob))
+                    },
+                    CHECKED_BUILD,
+                )),
                 EqualsTo => Some(impl_op!(Blob == Blob)),
                 NotEqualsTo => Some(impl_op!(Blob != Blob)),
                 _ => None,
@@ -298,9 +294,9 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
 
         if type1 == TypeId::of::<()>() {
             return match op {
-                EqualsTo => Some(const_true_fn),
+                EqualsTo => Some((const_true_fn, false)),
                 NotEqualsTo | GreaterThan | GreaterThanEqualsTo | LessThan | LessThanEqualsTo => {
-                    Some(const_false_fn)
+                    Some((const_false_fn, false))
                 }
                 _ => None,
             };
@@ -393,8 +389,8 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
     // char op string
     if (type1, type2) == (TypeId::of::<char>(), TypeId::of::<ImmutableString>()) {
         fn get_s1s2(args: &FnCallArgs) -> ([char; 2], [char; 2]) {
-            let x = args[0].as_char().expect(BUILTIN);
-            let y = &*args[1].read_lock::<ImmutableString>().expect(BUILTIN);
+            let x = args[0].as_char().unwrap();
+            let y = &*args[1].read_lock::<ImmutableString>().unwrap();
             let s1 = [x, '\0'];
             let mut y = y.chars();
             let s2 = [y.next().unwrap_or('\0'), y.next().unwrap_or('\0')];
@@ -402,20 +398,22 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
         }
 
         return match op {
-            Plus => Some(|_ctx, args| {
-                let x = args[0].as_char().expect(BUILTIN);
-                let y = &*args[1].read_lock::<ImmutableString>().expect(BUILTIN);
+            Plus => Some((
+                |_ctx, args| {
+                    let x = args[0].as_char().unwrap();
+                    let y = &*args[1].read_lock::<ImmutableString>().unwrap();
 
                     let mut result = SmartString::new_const();
                     result.push(x);
                     result.push_str(y);
 
                     #[cfg(not(feature = "unchecked"))]
-                _ctx.engine()
-                    .raise_err_if_over_data_size_limit((0, 0, result.len()))?;
+                    _ctx.unwrap().engine().throw_on_size((0, 0, result.len()))?;
 
                     Ok(result.into())
-            }),
+                },
+                CHECKED_BUILD,
+            )),
             EqualsTo => Some(impl_op!(get_s1s2(==))),
             NotEqualsTo => Some(impl_op!(get_s1s2(!=))),
             GreaterThan => Some(impl_op!(get_s1s2(>))),
@@ -428,8 +426,8 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
     // string op char
     if (type1, type2) == (TypeId::of::<ImmutableString>(), TypeId::of::<char>()) {
         fn get_s1s2(args: &FnCallArgs) -> ([char; 2], [char; 2]) {
-            let x = &*args[0].read_lock::<ImmutableString>().expect(BUILTIN);
-            let y = args[1].as_char().expect(BUILTIN);
+            let x = &*args[0].read_lock::<ImmutableString>().unwrap();
+            let y = args[1].as_char().unwrap();
             let mut x = x.chars();
             let s1 = [x.next().unwrap_or('\0'), x.next().unwrap_or('\0')];
             let s2 = [y, '\0'];
@@ -437,22 +435,27 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
         }
 
         return match op {
-            Plus => Some(|_ctx, args| {
-                let x = &*args[0].read_lock::<ImmutableString>().expect(BUILTIN);
-                let y = args[1].as_char().expect(BUILTIN);
+            Plus => Some((
+                |_ctx, args| {
+                    let x = &*args[0].read_lock::<ImmutableString>().unwrap();
+                    let y = args[1].as_char().unwrap();
                     let result = x + y;
 
                     #[cfg(not(feature = "unchecked"))]
-                _ctx.engine()
-                    .raise_err_if_over_data_size_limit((0, 0, result.len()))?;
+                    _ctx.unwrap().engine().throw_on_size((0, 0, result.len()))?;
 
                     Ok(result.into())
-            }),
-            Minus => Some(|_, args| {
-                let x = &*args[0].read_lock::<ImmutableString>().expect(BUILTIN);
-                let y = args[1].as_char().expect(BUILTIN);
+                },
+                CHECKED_BUILD,
+            )),
+            Minus => Some((
+                |_, args| {
+                    let x = &*args[0].read_lock::<ImmutableString>().unwrap();
+                    let y = args[1].as_char().unwrap();
                     Ok((x - y).into())
-            }),
+                },
+                false,
+            )),
             EqualsTo => Some(impl_op!(get_s1s2(==))),
             NotEqualsTo => Some(impl_op!(get_s1s2(!=))),
             GreaterThan => Some(impl_op!(get_s1s2(>))),
@@ -465,22 +468,22 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
     // () op string
     if (type1, type2) == (TypeId::of::<()>(), TypeId::of::<ImmutableString>()) {
         return match op {
-            Plus => Some(|_, args| Ok(args[1].clone())),
+            Plus => Some((|_, args| Ok(args[1].clone()), false)),
             EqualsTo | GreaterThan | GreaterThanEqualsTo | LessThan | LessThanEqualsTo => {
-                Some(const_false_fn)
+                Some((const_false_fn, false))
             }
-            NotEqualsTo => Some(const_true_fn),
+            NotEqualsTo => Some((const_true_fn, false)),
             _ => None,
         };
     }
     // string op ()
     if (type1, type2) == (TypeId::of::<ImmutableString>(), TypeId::of::<()>()) {
         return match op {
-            Plus => Some(|_, args| Ok(args[0].clone())),
+            Plus => Some((|_, args| Ok(args[0].clone()), false)),
             EqualsTo | GreaterThan | GreaterThanEqualsTo | LessThan | LessThanEqualsTo => {
-                Some(const_false_fn)
+                Some((const_false_fn, false))
             }
-            NotEqualsTo => Some(const_true_fn),
+            NotEqualsTo => Some((const_true_fn, false)),
             _ => None,
         };
     }
@@ -492,21 +495,22 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
 
         if type2 == TypeId::of::<char>() {
             return match op {
-                Plus => Some(|_ctx, args| {
-                    let mut blob = args[0].read_lock::<Blob>().expect(BUILTIN).clone();
+                Plus => Some((
+                    |_ctx, args| {
+                        let mut blob = args[0].read_lock::<Blob>().unwrap().clone();
                         let mut buf = [0_u8; 4];
-                    let x = args[1].as_char().expect(BUILTIN).encode_utf8(&mut buf);
+                        let x = args[1].as_char().unwrap().encode_utf8(&mut buf);
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine().raise_err_if_over_data_size_limit((
-                        blob.len() + x.len(),
-                        0,
-                        0,
-                    ))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((blob.len() + x.len(), 0, 0))?;
 
                         blob.extend(x.as_bytes());
                         Ok(Dynamic::from_blob(blob))
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }
@@ -525,8 +529,8 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
             )
     {
         return match op {
-            NotEqualsTo => Some(const_true_fn),
-            Equals => Some(const_false_fn),
+            NotEqualsTo => Some((const_true_fn, false)),
+            Equals => Some((const_false_fn, false)),
             _ => None,
         };
     }
@@ -556,9 +560,9 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
         } else if type1 != type2 {
             // If the types are not the same, default to not compare
             match op {
-                NotEqualsTo => Some(const_true_fn),
+                NotEqualsTo => Some((const_true_fn, false)),
                 EqualsTo | GreaterThan | GreaterThanEqualsTo | LessThan | LessThanEqualsTo => {
-                    Some(const_false_fn)
+                    Some((const_false_fn, false))
                 }
                 _ => None,
             }
@@ -571,9 +575,9 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
     // Default comparison operators for different types
     if type2 != type1 {
         return match op {
-            NotEqualsTo => Some(const_true_fn),
+            NotEqualsTo => Some((const_true_fn, false)),
             EqualsTo | GreaterThan | GreaterThanEqualsTo | LessThan | LessThanEqualsTo => {
-                Some(const_false_fn)
+                Some((const_false_fn, false))
             }
             _ => None,
         };
@@ -587,48 +591,48 @@ pub fn get_builtin_binary_op_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<
 ///
 /// The return function is registered as a _method_, so the first parameter cannot be consumed.
 #[must_use]
-pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Option<FnBuiltin> {
+pub fn get_builtin_op_assignment_fn(op: Token, x: &Dynamic, y: &Dynamic) -> Option<FnBuiltin> {
     let type1 = x.type_id();
     let type2 = y.type_id();
 
     macro_rules! impl_op {
-        ($x:ty = x $op:tt $yy:ident) => { |_, args| {
-            let x = args[0].$yy().expect(BUILTIN);
-            let y = args[1].$yy().expect(BUILTIN) as $x;
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) = x $op y).into())
-        } };
-        ($x:ident $op:tt $yy:ident) => { |_, args| {
-            let y = args[1].$yy().expect(BUILTIN) as $x;
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) $op y).into())
-        } };
-        ($x:ident $op:tt $yy:ident as $yyy:ty) => { |_, args| {
-            let y = args[1].$yy().expect(BUILTIN) as $yyy;
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) $op y).into())
-        } };
-        ($x:ty => $xx:ident . $func:ident ( $yy:ident as $yyy:ty )) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN);
-            let y = args[1].$yy().expect(BUILTIN) as $x;
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) = x.$func(y as $yyy)).into())
-        } };
-        ($x:ty => $func:ident ( $xx:ident, $yy:ident )) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN);
-            let y = args[1].$yy().expect(BUILTIN) as $x;
-            Ok((*args[0].write_lock().expect(BUILTIN) = $func(x, y)?).into())
-        } };
-        (from $x:ident $op:tt $yy:ident) => { |_, args| {
-            let y = <$x>::from(args[1].$yy().expect(BUILTIN));
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) $op y).into())
-        } };
-        (from $x:ty => $xx:ident . $func:ident ( $yy:ident )) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN);
-            let y = <$x>::from(args[1].$yy().expect(BUILTIN));
-            Ok((*args[0].write_lock::<$x>().expect(BUILTIN) = x.$func(y)).into())
-        } };
-        (from $x:ty => $func:ident ( $xx:ident, $yy:ident )) => { |_, args| {
-            let x = args[0].$xx().expect(BUILTIN);
-            let y = <$x>::from(args[1].$yy().expect(BUILTIN));
-            Ok((*args[0].write_lock().expect(BUILTIN) = $func(x, y)?).into())
-        } };
+        ($x:ty = x $op:tt $yy:ident) => { (|_, args| {
+            let x = args[0].$yy().unwrap();
+            let y = args[1].$yy().unwrap() as $x;
+            Ok((*args[0].write_lock::<$x>().unwrap() = x $op y).into())
+        }, false) };
+        ($x:ident $op:tt $yy:ident) => { (|_, args| {
+            let y = args[1].$yy().unwrap() as $x;
+            Ok((*args[0].write_lock::<$x>().unwrap() $op y).into())
+        }, false) };
+        ($x:ident $op:tt $yy:ident as $yyy:ty) => { (|_, args| {
+            let y = args[1].$yy().unwrap() as $yyy;
+            Ok((*args[0].write_lock::<$x>().unwrap() $op y).into())
+        }, false) };
+        ($x:ty => $xx:ident . $func:ident ( $yy:ident as $yyy:ty )) => { (|_, args| {
+            let x = args[0].$xx().unwrap();
+            let y = args[1].$yy().unwrap() as $x;
+            Ok((*args[0].write_lock::<$x>().unwrap() = x.$func(y as $yyy)).into())
+        }, false) };
+        ($x:ty => $func:ident ( $xx:ident, $yy:ident )) => { (|_, args| {
+            let x = args[0].$xx().unwrap();
+            let y = args[1].$yy().unwrap() as $x;
+            Ok((*args[0].write_lock().unwrap() = $func(x, y)?).into())
+        }, false) };
+        (from $x:ident $op:tt $yy:ident) => { (|_, args| {
+            let y = <$x>::from(args[1].$yy().unwrap());
+            Ok((*args[0].write_lock::<$x>().unwrap() $op y).into())
+        }, false) };
+        (from $x:ty => $xx:ident . $func:ident ( $yy:ident )) => { (|_, args| {
+            let x = args[0].$xx().unwrap();
+            let y = <$x>::from(args[1].$yy().unwrap());
+            Ok((*args[0].write_lock::<$x>().unwrap() = x.$func(y)).into())
+        }, false) };
+        (from $x:ty => $func:ident ( $xx:ident, $yy:ident )) => { (|_, args| {
+            let x = args[0].$xx().unwrap();
+            let y = <$x>::from(args[1].$yy().unwrap());
+            Ok((*args[0].write_lock().unwrap() = $func(x, y)?).into())
+        }, false) };
     }
 
     // Check for common patterns
@@ -682,42 +686,50 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
 
         if type1 == TypeId::of::<char>() {
             return match op {
-                PlusAssign => Some(|_, args| {
-                    let y = args[1].as_char().expect(BUILTIN);
-                    let x = &mut *args[0].write_lock::<Dynamic>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_, args| {
+                        let y = args[1].as_char().unwrap();
+                        let x = &mut *args[0].write_lock::<Dynamic>().unwrap();
 
                         let mut buf = SmartString::new_const();
                         write!(&mut buf, "{y}").unwrap();
                         buf.push(y);
 
                         Ok((*x = buf.into()).into())
-                }),
+                    },
+                    false,
+                )),
                 _ => None,
             };
         }
 
         if type1 == TypeId::of::<ImmutableString>() {
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let (first, second) = args.split_first_mut().expect(BUILTIN);
-                    let x = &mut *first.write_lock::<ImmutableString>().expect(BUILTIN);
-                    let y = &*second[0].read_lock::<ImmutableString>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let (first, second) = args.split_first_mut().unwrap();
+                        let x = &mut *first.write_lock::<ImmutableString>().unwrap();
+                        let y = &*second[0].read_lock::<ImmutableString>().unwrap();
 
                         #[cfg(not(feature = "unchecked"))]
                         if !x.is_empty() && !y.is_empty() {
                             let total_len = x.len() + y.len();
-                        _ctx.engine()
-                            .raise_err_if_over_data_size_limit((0, 0, total_len))?;
+                            _ctx.unwrap().engine().throw_on_size((0, 0, total_len))?;
                         }
 
                         Ok((*x += y).into())
-                }),
-                MinusAssign => Some(|_, args| {
-                    let (first, second) = args.split_first_mut().expect(BUILTIN);
-                    let x = &mut *first.write_lock::<ImmutableString>().expect(BUILTIN);
-                    let y = &*second[0].read_lock::<ImmutableString>().expect(BUILTIN);
+                    },
+                    CHECKED_BUILD,
+                )),
+                MinusAssign => Some((
+                    |_, args| {
+                        let (first, second) = args.split_first_mut().unwrap();
+                        let x = &mut *first.write_lock::<ImmutableString>().unwrap();
+                        let y = &*second[0].read_lock::<ImmutableString>().unwrap();
                         Ok((*x -= y).into())
-                }),
+                    },
+                    false,
+                )),
                 _ => None,
             };
         }
@@ -729,27 +741,30 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
             use crate::Array;
 
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let x = std::mem::take(args[1]).into_array().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let x = std::mem::take(args[1]).into_array().unwrap();
 
                         if x.is_empty() {
                             return Ok(Dynamic::UNIT);
                         }
 
-                    let _array_is_empty = args[0].read_lock::<Array>().expect(BUILTIN).is_empty();
+                        let _array_is_empty = args[0].read_lock::<Array>().unwrap().is_empty();
 
                         #[cfg(not(feature = "unchecked"))]
                         if !_array_is_empty {
-                        _ctx.engine().check_data_size(
-                            &*args[0].read_lock().expect(BUILTIN),
+                            _ctx.unwrap().engine().check_data_size(
+                                &*args[0].read_lock().unwrap(),
                                 crate::Position::NONE,
                             )?;
                         }
 
-                    let array = &mut *args[0].write_lock::<Array>().expect(BUILTIN);
+                        let array = &mut *args[0].write_lock::<Array>().unwrap();
 
                         Ok(append(array, x).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }
@@ -761,19 +776,20 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
             use crate::Blob;
 
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let blob2 = std::mem::take(args[1]).into_blob().expect(BUILTIN);
-                    let blob1 = &mut *args[0].write_lock::<Blob>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let blob2 = std::mem::take(args[1]).into_blob().unwrap();
+                        let blob1 = &mut *args[0].write_lock::<Blob>().unwrap();
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine().raise_err_if_over_data_size_limit((
-                        blob1.len() + blob2.len(),
-                        0,
-                        0,
-                    ))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((blob1.len() + blob2.len(), 0, 0))?;
 
                         Ok(append(blob1, blob2).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }
@@ -847,17 +863,21 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
     // string op= char
     if (type1, type2) == (TypeId::of::<ImmutableString>(), TypeId::of::<char>()) {
         return match op {
-            PlusAssign => Some(|_ctx, args| {
+            PlusAssign => Some((
+                |_ctx, args| {
                     let mut buf = [0_u8; 4];
-                let ch = &*args[1].as_char().expect(BUILTIN).encode_utf8(&mut buf);
-                let mut x = args[0].write_lock::<ImmutableString>().expect(BUILTIN);
+                    let ch = &*args[1].as_char().unwrap().encode_utf8(&mut buf);
+                    let mut x = args[0].write_lock::<ImmutableString>().unwrap();
 
                     #[cfg(not(feature = "unchecked"))]
-                _ctx.engine()
-                    .raise_err_if_over_data_size_limit((0, 0, x.len() + ch.len()))?;
+                    _ctx.unwrap()
+                        .engine()
+                        .throw_on_size((0, 0, x.len() + ch.len()))?;
 
                     Ok((*x += ch).into())
-            }),
+                },
+                CHECKED_BUILD,
+            )),
             MinusAssign => Some(impl_op!(ImmutableString -= as_char as char)),
             _ => None,
         };
@@ -865,28 +885,32 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
     // char op= string
     if (type1, type2) == (TypeId::of::<char>(), TypeId::of::<ImmutableString>()) {
         return match op {
-            PlusAssign => Some(|_ctx, args| {
+            PlusAssign => Some((
+                |_ctx, args| {
                     let ch = {
-                    let s = &*args[1].read_lock::<ImmutableString>().expect(BUILTIN);
+                        let s = &*args[1].read_lock::<ImmutableString>().unwrap();
 
                         if s.is_empty() {
                             return Ok(Dynamic::UNIT);
                         }
 
-                    let mut ch = args[0].as_char().expect(BUILTIN).to_string();
+                        let mut ch = args[0].as_char().unwrap().to_string();
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine()
-                        .raise_err_if_over_data_size_limit((0, 0, ch.len() + s.len()))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((0, 0, ch.len() + s.len()))?;
 
                         ch.push_str(s);
                         ch
                     };
 
-                *args[0].write_lock::<Dynamic>().expect(BUILTIN) = ch.into();
+                    *args[0].write_lock::<Dynamic>().unwrap() = ch.into();
 
                     Ok(Dynamic::UNIT)
-            }),
+                },
+                CHECKED_BUILD,
+            )),
             _ => None,
         };
     }
@@ -899,21 +923,23 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
         use crate::Array;
 
         return match op {
-            PlusAssign => Some(|_ctx, args| {
+            PlusAssign => Some((
+                |_ctx, args| {
                     {
                         let x = std::mem::take(args[1]);
-                    let array = &mut *args[0].write_lock::<Array>().expect(BUILTIN);
+                        let array = &mut *args[0].write_lock::<Array>().unwrap();
                         push(array, x);
                     }
 
                     #[cfg(not(feature = "unchecked"))]
-                _ctx.engine().check_data_size(
-                    &*args[0].read_lock().expect(BUILTIN),
-                    crate::Position::NONE,
-                )?;
+                    _ctx.unwrap()
+                        .engine()
+                        .check_data_size(&*args[0].read_lock().unwrap(), crate::Position::NONE)?;
 
                     Ok(Dynamic::UNIT)
-            }),
+                },
+                CHECKED_BUILD,
+            )),
             _ => None,
         };
     }
@@ -928,16 +954,20 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
             use crate::packages::blob_basic::blob_functions::*;
 
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let x = args[1].as_int().expect(BUILTIN);
-                    let blob = &mut *args[0].write_lock::<Blob>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let x = args[1].as_int().unwrap();
+                        let blob = &mut *args[0].write_lock::<Blob>().unwrap();
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine()
-                        .raise_err_if_over_data_size_limit((blob.len() + 1, 0, 0))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((blob.len() + 1, 0, 0))?;
 
                         Ok(push(blob, x).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }
@@ -948,16 +978,20 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
             use crate::packages::blob_basic::blob_functions::*;
 
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let x = args[1].as_char().expect(BUILTIN);
-                    let blob = &mut *args[0].write_lock::<Blob>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let x = args[1].as_char().unwrap();
+                        let blob = &mut *args[0].write_lock::<Blob>().unwrap();
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine()
-                        .raise_err_if_over_data_size_limit((blob.len() + 1, 0, 0))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((blob.len() + 1, 0, 0))?;
 
                         Ok(append_char(blob, x).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }
@@ -968,24 +1002,25 @@ pub fn get_builtin_op_assignment_fn(op: &Token, x: &Dynamic, y: &Dynamic) -> Opt
             use crate::packages::blob_basic::blob_functions::*;
 
             return match op {
-                PlusAssign => Some(|_ctx, args| {
-                    let (first, second) = args.split_first_mut().expect(BUILTIN);
-                    let blob = &mut *first.write_lock::<Blob>().expect(BUILTIN);
-                    let s = &*second[0].read_lock::<ImmutableString>().expect(BUILTIN);
+                PlusAssign => Some((
+                    |_ctx, args| {
+                        let (first, second) = args.split_first_mut().unwrap();
+                        let blob = &mut *first.write_lock::<Blob>().unwrap();
+                        let s = &*second[0].read_lock::<ImmutableString>().unwrap();
 
                         if s.is_empty() {
                             return Ok(Dynamic::UNIT);
                         }
 
                         #[cfg(not(feature = "unchecked"))]
-                    _ctx.engine().raise_err_if_over_data_size_limit((
-                        blob.len() + s.len(),
-                        0,
-                        0,
-                    ))?;
+                        _ctx.unwrap()
+                            .engine()
+                            .throw_on_size((blob.len() + s.len(), 0, 0))?;
 
                         Ok(append_str(blob, s).into())
-                }),
+                    },
+                    CHECKED_BUILD,
+                )),
                 _ => None,
             };
         }

src/func/call.rs

@@ -8,8 +8,7 @@ use crate::engine::{
     KEYWORD_IS_DEF_VAR, KEYWORD_PRINT, KEYWORD_TYPE_OF,
 };
 use crate::eval::{Caches, FnResolutionCacheEntry, GlobalRuntimeState};
-use crate::tokenizer::{is_valid_function_name, Token};
-use crate::types::RestoreOnDrop;
+use crate::tokenizer::{is_valid_function_name, Token, NO_TOKEN};
 use crate::{
     calc_fn_hash, calc_fn_hash_full, Dynamic, Engine, FnArgsVec, FnPtr, ImmutableString,
     OptimizationLevel, Position, RhaiError, RhaiResult, RhaiResultOf, Scope, Shared, ERR,
@@ -165,7 +164,7 @@ impl Engine {
         _global: &GlobalRuntimeState,
         caches: &'s mut Caches,
         local_entry: &'s mut Option<FnResolutionCacheEntry>,
-        op_token: Option<&Token>,
+        op_token: Token,
         hash_base: u64,
         args: Option<&mut FnCallArgs>,
         allow_dynamic: bool,
@@ -174,7 +173,7 @@ impl Engine {
             return None;
         }
 
-        let mut hash = args.as_ref().map_or(hash_base, |args| {
+        let mut hash = args.as_deref().map_or(hash_base, |args| {
             calc_fn_hash_full(hash_base, args.iter().map(|a| a.type_id()))
         });
 
@@ -183,7 +182,7 @@ impl Engine {
         match cache.map.entry(hash) {
             Entry::Occupied(entry) => entry.into_mut().as_ref(),
             Entry::Vacant(entry) => {
-                let num_args = args.as_ref().map_or(0, |a| a.len());
+                let num_args = args.as_deref().map_or(0, |a| a.len());
                 let mut max_bitmask = 0; // One above maximum bitmask based on number of parameters.
                                          // Set later when a specific matching function is not found.
                 let mut bitmask = 1usize; // Bitmask of which parameter to replace with `Dynamic`
@@ -212,9 +211,12 @@ impl Engine {
                     } else {
                         func.or_else(|| _global.get_qualified_fn(hash)).or_else(|| {
                             self.global_sub_modules
-                                .iter()
-                                .flat_map(|m| m.values())
-                                .find_map(|m| m.get_qualified_fn(hash).map(|f| (f, m.id_raw())))
+                                .as_deref()
+                                .into_iter()
+                                .flatten()
+                                .find_map(|(_, m)| {
+                                    m.get_qualified_fn(hash).map(|f| (f, m.id_raw()))
+                                })
                         })
                     };
 
@@ -251,11 +253,9 @@ impl Engine {
                         #[cfg(not(feature = "no_module"))]
                         let is_dynamic = is_dynamic
                             || _global.may_contain_dynamic_fn(hash_base)
-                            || self
-                                .global_sub_modules
-                                .iter()
-                                .flat_map(|m| m.values())
-                                .any(|m| m.may_contain_dynamic_fn(hash_base));
+                            || self.global_sub_modules.as_deref().map_or(false, |m| {
+                                m.values().any(|m| m.may_contain_dynamic_fn(hash_base))
+                            });
 
                         // Set maximum bitmask when there are dynamic versions of the function
                         if is_dynamic {
@@ -272,22 +272,22 @@ impl Engine {
                         // Try to find a built-in version
                         let builtin =
                             args.and_then(|args| match op_token {
-                                Some(token) if token.is_op_assignment() => {
+                                Token::NONE => None,
+                                token if token.is_op_assignment() => {
                                     let (first_arg, rest_args) = args.split_first().unwrap();
 
                                     get_builtin_op_assignment_fn(token, first_arg, rest_args[0])
-                                        .map(|f| FnResolutionCacheEntry {
-                                            func: CallableFunction::Method(Shared::new(f)),
+                                        .map(|(f, ctx)| FnResolutionCacheEntry {
+                                            func: CallableFunction::Method(Shared::new(f), ctx),
                                             source: None,
                                         })
                                 }
-                                Some(token) => get_builtin_binary_op_fn(token, args[0], args[1])
-                                    .map(|f| FnResolutionCacheEntry {
-                                        func: CallableFunction::Method(Shared::new(f)),
+                                token => get_builtin_binary_op_fn(token, args[0], args[1]).map(
+                                    |(f, ctx)| FnResolutionCacheEntry {
+                                        func: CallableFunction::Method(Shared::new(f), ctx),
                                         source: None,
-                                    }),
-
-                                None => None,
+                                    },
+                                ),
                             });
 
                         return if cache.filter.is_absent_and_set(hash) {
@@ -324,9 +324,9 @@ impl Engine {
         }
     }
 
-    /// # Main Entry-Point
+    /// # Main Entry-Point (Native by Name)
     ///
-    /// Call a native Rust function registered with the [`Engine`].
+    /// Call a native Rust function registered with the [`Engine`] by name.
     ///
     /// # WARNING
     ///
@@ -340,7 +340,7 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         name: &str,
-        op_token: Option<&Token>,
+        op_token: Token,
         hash: u64,
         args: &mut FnCallArgs,
         is_ref_mut: bool,
@@ -380,12 +380,10 @@ impl Engine {
                 // Clone the first argument
                 backup.change_first_arg_to_copy(args);
             }
-
-            let args =
-                &mut *RestoreOnDrop::lock_if(swap, args, move |a| backup.restore_first_arg(a));
+            auto_restore!(args if swap => move |a| backup.restore_first_arg(a));
 
             #[cfg(feature = "debugging")]
-            if self.debugger.is_some() {
+            if self.is_debugger_registered() {
                 let source = source.clone().or_else(|| global.source.clone());
 
                 global.debugger_mut().push_call_stack_frame(
@@ -399,25 +397,29 @@ impl Engine {
             // Run external function
             let is_method = func.is_method();
             let src = source.as_ref().map(|s| s.as_str());
-            let context = (self, name, src, &*global, pos).into();
 
-            let mut _result = if func.is_plugin_fn() {
-                let f = func.get_plugin_fn().unwrap();
+            let context = if func.has_context() {
+                Some((self, name, src, &*global, pos).into())
+            } else {
+                None
+            };
+
+            let mut _result = if let Some(f) = func.get_plugin_fn() {
                 if !f.is_pure() && !args.is_empty() && args[0].is_read_only() {
                     Err(ERR::ErrorNonPureMethodCallOnConstant(name.to_string(), pos).into())
                 } else {
                     f.call(context, args)
-                        .and_then(|r| self.check_data_size(r, pos))
-                        .map_err(|err| err.fill_position(pos))
                 }
+            } else if let Some(f) = func.get_native_fn() {
+                f(context, args)
             } else {
-                func.get_native_fn().unwrap()(context, args)
+                unreachable!();
+            }
             .and_then(|r| self.check_data_size(r, pos))
-                    .map_err(|err| err.fill_position(pos))
-            };
+            .map_err(|err| err.fill_position(pos));
 
             #[cfg(feature = "debugging")]
-            if self.debugger.is_some() {
+            if self.is_debugger_registered() {
                 use crate::eval::{DebuggerEvent, DebuggerStatus};
 
                 let trigger = match global.debugger().status {
@@ -542,9 +544,9 @@ impl Engine {
         }
     }
 
-    /// # Main Entry-Point
+    /// # Main Entry-Point (By Name)
     ///
-    /// Perform an actual function call, native Rust or scripted, taking care of special functions.
+    /// Perform an actual function call, native Rust or scripted, by name, taking care of special functions.
     ///
     /// # WARNING
     ///
@@ -559,7 +561,7 @@ impl Engine {
         caches: &mut Caches,
         _scope: Option<&mut Scope>,
         fn_name: &str,
-        op_token: Option<&Token>,
+        op_token: Token,
         hashes: FnCallHashes,
         mut _args: &mut FnCallArgs,
         is_ref_mut: bool,
@@ -578,9 +580,7 @@ impl Engine {
         #[cfg(not(feature = "no_closure"))]
         ensure_no_data_race(fn_name, _args, is_ref_mut)?;
 
-        let orig_level = global.level;
-        global.level += 1;
-        let global = &mut *RestoreOnDrop::lock(global, move |g| g.level = orig_level);
+        auto_restore! { let orig_level = global.level; global.level += 1 }
 
         // These may be redirected from method style calls.
         if hashes.is_native_only() {
@@ -638,7 +638,7 @@ impl Engine {
             let local_entry = &mut None;
 
             if let Some(FnResolutionCacheEntry { func, ref source }) = self
-                .resolve_fn(global, caches, local_entry, None, hash, None, false)
+                .resolve_fn(global, caches, local_entry, NO_TOKEN, hash, None, false)
                 .cloned()
             {
                 // Script function call
@@ -659,7 +659,7 @@ impl Engine {
                 };
 
                 let orig_source = mem::replace(&mut global.source, source.clone());
-                let global = &mut *RestoreOnDrop::lock(global, move |g| g.source = orig_source);
+                auto_restore!(global => move |g| g.source = orig_source);
 
                 return if _is_method_call {
                     // Method call of script function - map first argument to `this`
@@ -679,9 +679,7 @@ impl Engine {
                         backup.change_first_arg_to_copy(_args);
                     }
 
-                    let args = &mut *RestoreOnDrop::lock_if(swap, _args, move |a| {
-                        backup.restore_first_arg(a)
-                    });
+                    auto_restore!(args = (_args) if swap => move |a| backup.restore_first_arg(a));
 
                     let mut this = Dynamic::NULL;
 
@@ -721,15 +719,13 @@ impl Engine {
 
         // Do not match function exit for arguments
         #[cfg(feature = "debugging")]
-        let reset = global.debugger.as_mut().and_then(|dbg| {
+        let reset = global.debugger.as_deref_mut().and_then(|dbg| {
             dbg.clear_status_if(|status| {
                 matches!(status, crate::eval::DebuggerStatus::FunctionExit(..))
             })
         });
         #[cfg(feature = "debugging")]
-        let global = &mut *RestoreOnDrop::lock_if(reset.is_some(), global, move |g| {
-            g.debugger_mut().reset_status(reset)
-        });
+        auto_restore!(global if reset.is_some() => move |g| g.debugger_mut().reset_status(reset));
 
         self.eval_expr(global, caches, scope, this_ptr, arg_expr)
             .map(|r| (r, arg_expr.start_position()))
@@ -782,7 +778,7 @@ impl Engine {
                     caches,
                     None,
                     fn_name,
-                    None,
+                    NO_TOKEN,
                     new_hash,
                     &mut args,
                     false,
@@ -836,7 +832,7 @@ impl Engine {
                     caches,
                     None,
                     &fn_name,
-                    None,
+                    NO_TOKEN,
                     new_hash,
                     &mut args,
                     is_ref_mut,
@@ -935,7 +931,7 @@ impl Engine {
                     caches,
                     None,
                     fn_name,
-                    None,
+                    NO_TOKEN,
                     hash,
                     &mut args,
                     is_ref_mut,
@@ -961,7 +957,7 @@ impl Engine {
         scope: &mut Scope,
         this_ptr: &mut Dynamic,
         fn_name: &str,
-        op_token: Option<&Token>,
+        op_token: Token,
         first_arg: Option<&Expr>,
         args_expr: &[Expr],
         hashes: FnCallHashes,
@@ -977,7 +973,7 @@ impl Engine {
         let redirected; // Handle call() - Redirect function call
 
         match name {
-            _ if op_token.is_some() => (),
+            _ if op_token != NO_TOKEN => (),
 
             // Handle call()
             KEYWORD_FN_PTR_CALL if total_args >= 1 => {
@@ -1208,12 +1204,7 @@ impl Engine {
 
                 self.track_operation(global, first_expr.position())?;
 
-                #[cfg(not(feature = "no_closure"))]
-                let target_is_shared = target.is_shared();
-                #[cfg(feature = "no_closure")]
-                let target_is_shared = false;
-
-                if target_is_shared || target.is_temp_value() {
+                if target.is_shared() || target.is_temp_value() {
                     arg_values.insert(0, target.take_or_clone().flatten());
                 } else {
                     // Turn it into a method call only if the object is not shared and not a simple value
@@ -1370,9 +1361,7 @@ impl Engine {
             }
         }
 
-        let orig_level = global.level;
-        global.level += 1;
-        let global = &mut *RestoreOnDrop::lock(global, move |g| g.level = orig_level);
+        auto_restore! { let orig_level = global.level; global.level += 1 }
 
         match func {
             #[cfg(not(feature = "no_function"))]
@@ -1382,7 +1371,7 @@ impl Engine {
                 let mut this = Dynamic::NULL;
 
                 let orig_source = mem::replace(&mut global.source, module.id_raw().cloned());
-                let global = &mut *RestoreOnDrop::lock(global, move |g| g.source = orig_source);
+                auto_restore!(global => move |g| g.source = orig_source);
 
                 self.call_script_fn(
                     global, caches, new_scope, &mut this, fn_def, &mut args, true, pos,
@@ -1390,8 +1379,12 @@ impl Engine {
             }
 
             Some(f) if f.is_plugin_fn() => {
-                let context = (self, fn_name, module.id(), &*global, pos).into();
                 let f = f.get_plugin_fn().expect("plugin function");
+                let context = if f.has_context() {
+                    Some((self, fn_name, module.id(), &*global, pos).into())
+                } else {
+                    None
+                };
                 if !f.is_pure() && !args.is_empty() && args[0].is_read_only() {
                     Err(ERR::ErrorNonPureMethodCallOnConstant(fn_name.to_string(), pos).into())
                 } else {
@@ -1402,7 +1395,11 @@ impl Engine {
 
             Some(f) if f.is_native() => {
                 let func = f.get_native_fn().expect("native function");
-                let context = (self, fn_name, module.id(), &*global, pos).into();
+                let context = if f.has_context() {
+                    Some((self, fn_name, module.id(), &*global, pos).into())
+                } else {
+                    None
+                };
                 func(context, &mut args).and_then(|r| self.check_data_size(r, pos))
             }
 
@@ -1467,6 +1464,8 @@ impl Engine {
         self.eval_global_statements(global, caches, scope, statements)
     }
 
+    /// # Main Entry-Point (`FnCallExpr`)
+    ///
     /// Evaluate a function call expression.
     pub(crate) fn eval_fn_call_expr(
         &self,
@@ -1488,10 +1487,26 @@ impl Engine {
             ..
         } = expr;
 
-        let op_token = op_token.as_ref();
+        let op_token = op_token.clone();
+
+        // Short-circuit native unary operator call if under Fast Operators mode
+        if op_token == Token::Bang && self.fast_operators() && args.len() == 1 {
+            let mut value = self
+                .get_arg_value(global, caches, scope, this_ptr, &args[0])?
+                .0
+                .flatten();
+
+            return value.as_bool().and_then(|r| Ok((!r).into())).or_else(|_| {
+                let operand = &mut [&mut value];
+                self.exec_fn_call(
+                    global, caches, None, name, op_token, *hashes, operand, false, false, pos,
+                )
+                .map(|(v, ..)| v)
+            });
+        }
 
         // Short-circuit native binary operator call if under Fast Operators mode
-        if op_token.is_some() && self.fast_operators() && args.len() == 2 {
+        if op_token != NO_TOKEN && self.fast_operators() && args.len() == 2 {
             let mut lhs = self
                 .get_arg_value(global, caches, scope, this_ptr, &args[0])?
                 .0
@@ -1504,15 +1519,17 @@ impl Engine {
 
             let operands = &mut [&mut lhs, &mut rhs];
 
-            if let Some(func) =
-                get_builtin_binary_op_fn(op_token.as_ref().unwrap(), operands[0], operands[1])
+            if let Some((func, ctx)) =
+                get_builtin_binary_op_fn(op_token.clone(), operands[0], operands[1])
             {
                 // Built-in found
-                let orig_level = global.level;
-                global.level += 1;
-                let global = &*RestoreOnDrop::lock(global, move |g| g.level = orig_level);
+                auto_restore! { let orig_level = global.level; global.level += 1 }
 
-                let context = (self, name.as_str(), None, global, pos).into();
+                let context = if ctx {
+                    Some((self, name.as_str(), None, &*global, pos).into())
+                } else {
+                    None
+                };
                 return func(context, operands);
             }
 

src/func/callable_function.rs

@@ -14,10 +14,10 @@ use std::prelude::v1::*;
 #[non_exhaustive]
 pub enum CallableFunction {
     /// A pure native Rust function with all arguments passed by value.
-    Pure(Shared<FnAny>),
+    Pure(Shared<FnAny>, bool),
     /// A native Rust object method with the first argument passed by reference,
     /// and the rest passed by value.
-    Method(Shared<FnAny>),
+    Method(Shared<FnAny>, bool),
     /// An iterator function.
     Iterator(Shared<IteratorFn>),
     /// A plugin function,
@@ -136,6 +136,18 @@ impl CallableFunction {
             Self::Script(..) => false,
         }
     }
+    /// Is there a [`NativeCallContext`][crate::NativeCallContext] parameter?
+    #[inline]
+    #[must_use]
+    pub fn has_context(&self) -> bool {
+        match self {
+            Self::Pure(.., ctx) | Self::Method(.., ctx) => *ctx,
+            Self::Plugin(f) => f.has_context(),
+            Self::Iterator(..) => false,
+            #[cfg(not(feature = "no_function"))]
+            Self::Script(..) => false,
+        }
+    }
     /// Get the access mode.
     #[inline]
     #[must_use]
@@ -156,7 +168,7 @@ impl CallableFunction {
     #[must_use]
     pub fn get_native_fn(&self) -> Option<&Shared<FnAny>> {
         match self {
-            Self::Pure(f) | Self::Method(f) => Some(f),
+            Self::Pure(f, ..) | Self::Method(f, ..) => Some(f),
             Self::Iterator(..) | Self::Plugin(..) => None,
 
             #[cfg(not(feature = "no_function"))]
@@ -204,16 +216,16 @@ impl CallableFunction {
 #[cfg(not(feature = "no_function"))]
 impl From<crate::ast::ScriptFnDef> for CallableFunction {
     #[inline(always)]
-    fn from(_func: crate::ast::ScriptFnDef) -> Self {
-        Self::Script(_func.into())
+    fn from(func: crate::ast::ScriptFnDef) -> Self {
+        Self::Script(func.into())
     }
 }
 
 #[cfg(not(feature = "no_function"))]
 impl From<Shared<crate::ast::ScriptFnDef>> for CallableFunction {
     #[inline(always)]
-    fn from(_func: Shared<crate::ast::ScriptFnDef>) -> Self {
-        Self::Script(_func)
+    fn from(func: Shared<crate::ast::ScriptFnDef>) -> Self {
+        Self::Script(func)
     }
 }
 

src/func/func.rs

@@ -12,7 +12,7 @@ use std::prelude::v1::*;
 /// Trait to create a Rust closure from a script.
 ///
 /// Not available under `no_function`.
-pub trait Func<ARGS, RET> {
+pub trait Func<A, R> {
     /// The closure's output type.
     type Output;
 
@@ -91,14 +91,14 @@ macro_rules! def_anonymous_fn {
         impl<$($par: Variant + Clone,)* RET: Variant + Clone> Func<($($par,)*), RET> for Engine
         {
             #[cfg(feature = "sync")]
-            type Output = Box<dyn Fn($($par),*) -> RhaiResultOf<RET> + Send + Sync>;
+            type Output = Box<dyn Fn($($par,)*) -> RhaiResultOf<RET> + Send + Sync>;
             #[cfg(not(feature = "sync"))]
-            type Output = Box<dyn Fn($($par),*) -> RhaiResultOf<RET>>;
+            type Output = Box<dyn Fn($($par,)*) -> RhaiResultOf<RET>>;
 
             #[inline]
             fn create_from_ast(self, ast: AST, entry_point: &str) -> Self::Output {
                 let fn_name: SmartString = entry_point.into();
-                Box::new(move |$($par),*| self.call_fn(&mut Scope::new(), &ast, &fn_name, ($($par,)*)))
+                Box::new(move |$($par,)*| self.call_fn(&mut Scope::new(), &ast, &fn_name, ($($par,)*)))
             }
 
             #[inline]

src/func/native.rs

@@ -4,11 +4,11 @@ use super::call::FnCallArgs;
 use crate::ast::FnCallHashes;
 use crate::eval::{Caches, GlobalRuntimeState};
 use crate::plugin::PluginFunction;
-use crate::tokenizer::{is_valid_function_name, Token, TokenizeState};
+use crate::tokenizer::{is_valid_function_name, Token, TokenizeState, NO_TOKEN};
 use crate::types::dynamic::Variant;
 use crate::{
-    calc_fn_hash, reify, Dynamic, Engine, EvalContext, FuncArgs, Position, RhaiResult,
-    RhaiResultOf, StaticVec, VarDefInfo, ERR,
+    calc_fn_hash, Dynamic, Engine, EvalContext, FuncArgs, Position, RhaiResult, RhaiResultOf,
+    StaticVec, VarDefInfo, ERR,
 };
 use std::any::{type_name, TypeId};
 #[cfg(feature = "no_std")]
@@ -424,8 +424,7 @@ impl<'a> NativeCallContext<'a> {
         let caches = &mut Caches::new();
 
         let fn_name = fn_name.as_ref();
-        let op_token = Token::lookup_symbol_from_syntax(fn_name);
-        let op_token = op_token.as_ref();
+        let op_token = Token::lookup_symbol_from_syntax(fn_name).unwrap_or(NO_TOKEN);
         let args_len = args.len();
 
         global.level += 1;
@@ -547,13 +546,16 @@ pub fn locked_write<T>(value: &Locked<T>) -> LockGuardMut<T> {
 
 /// General Rust function trail object.
 #[cfg(not(feature = "sync"))]
-pub type FnAny = dyn Fn(NativeCallContext, &mut FnCallArgs) -> RhaiResult;
+pub type FnAny = dyn Fn(Option<NativeCallContext>, &mut FnCallArgs) -> RhaiResult;
 /// General Rust function trail object.
 #[cfg(feature = "sync")]
-pub type FnAny = dyn Fn(NativeCallContext, &mut FnCallArgs) -> RhaiResult + Send + Sync;
+pub type FnAny = dyn Fn(Option<NativeCallContext>, &mut FnCallArgs) -> RhaiResult + Send + Sync;
 
 /// Built-in function trait object.
-pub type FnBuiltin = fn(NativeCallContext, &mut FnCallArgs) -> RhaiResult;
+pub type FnBuiltin = (
+    fn(Option<NativeCallContext>, &mut FnCallArgs) -> RhaiResult,
+    bool,
+);
 
 /// Function that gets an iterator from a type.
 #[cfg(not(feature = "sync"))]

src/func/plugin.rs

@@ -24,12 +24,16 @@ pub use rhai_codegen::{export_fn, register_exported_fn};
 /// Use the `#[export_module]` and `#[export_fn]` procedural attributes instead.
 pub trait PluginFunction {
     /// Call the plugin function with the arguments provided.
-    fn call(&self, context: NativeCallContext, args: &mut FnCallArgs) -> RhaiResult;
+    fn call(&self, context: Option<NativeCallContext>, args: &mut FnCallArgs) -> RhaiResult;
 
     /// Is this plugin function a method?
     #[must_use]
     fn is_method_call(&self) -> bool;
 
+    /// Does this plugin function contain a [`NativeCallContext`] parameter?
+    #[must_use]
+    fn has_context(&self) -> bool;
+
     /// Is this plugin function pure?
     ///
     /// This defaults to `true` such that any old implementation that has constant-checking code

src/func/register.rs

@@ -1,15 +1,21 @@
 //! Module which defines the function registration mechanism.
 
 #![allow(non_snake_case)]
+#![allow(unused_imports)]
+#![allow(unused_mut)]
+#![allow(unused_variables)]
 
 use super::call::FnCallArgs;
 use super::callable_function::CallableFunction;
 use super::native::{SendSync, Shared};
 use crate::types::dynamic::{DynamicWriteLock, Variant};
-use crate::{reify, Dynamic, NativeCallContext, RhaiResultOf};
+use crate::{Dynamic, Identifier, NativeCallContext, RhaiResultOf};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
-use std::{any::TypeId, mem};
+use std::{
+    any::{type_name, TypeId},
+    mem,
+};
 
 /// These types are used to build a unique _marker_ tuple type for each combination
 /// of function parameter types in order to make each trait implementation unique.
@@ -19,13 +25,13 @@ use std::{any::TypeId, mem};
 ///
 /// # Examples
 ///
-/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), R, ()>` = `Fn(&mut A, B, &C) -> R`
+/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), 3, false, R, false>` = `Fn(&mut A, B, &C) -> R`
 ///
-/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), R, NativeCallContext>` = `Fn(NativeCallContext, &mut A, B, &C) -> R`
+/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), 3, true,  R, false>` = `Fn(NativeCallContext, &mut A, B, &C) -> R`
 ///
-/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), R, RhaiResultOf<()>>` = `Fn(&mut A, B, &C) -> Result<R, Box<EvalAltResult>>`
+/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), 3, false, R, true>`  = `Fn(&mut A, B, &C) -> Result<R, Box<EvalAltResult>>`
 ///
-/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), R, RhaiResultOf<NativeCallContext>>` = `Fn(NativeCallContext, &mut A, B, &C) -> Result<R, Box<EvalAltResult>>`
+/// `RegisterNativeFunction<(Mut<A>, B, Ref<C>), 3, true,  R, true>`  = `Fn(NativeCallContext, &mut A, B, &C) -> Result<R, Box<EvalAltResult>>`
 ///
 /// These types are not actually used anywhere.
 pub struct Mut<T>(T);
@@ -64,123 +70,137 @@ pub fn by_value<T: Variant + Clone>(data: &mut Dynamic) -> T {
 ///
 /// # Type Parameters
 ///
-/// * `ARGS` - a tuple containing parameter types, with `&mut T` represented by `Mut<T>`.
-/// * `RET` - return type of the function; if the function returns `Result`, it is the unwrapped inner value type.
-pub trait RegisterNativeFunction<ARGS, RET, RESULT> {
+/// * `A` - a tuple containing parameter types, with `&mut T` represented by `Mut<T>`.
+/// * `N` - a constant generic containing the number of parameters, must be consistent with `ARGS`.
+/// * `X` - a constant boolean generic indicating whether there is a `NativeCallContext` parameter.
+/// * `R` - return type of the function; if the function returns `Result`, it is the unwrapped inner value type.
+/// * `F` - a constant boolean generic indicating whether the function is fallible (i.e. returns `Result<T, Box<EvalAltResult>>`).
+pub trait RegisterNativeFunction<
+    A: 'static,
+    const N: usize,
+    const X: bool,
+    R: 'static,
+    const F: bool,
+>
+{
     /// Convert this function into a [`CallableFunction`].
     #[must_use]
-    fn into_callable_function(self) -> CallableFunction;
+    fn into_callable_function(self, name: Identifier, no_const: bool) -> CallableFunction;
     /// Get the type ID's of this function's parameters.
     #[must_use]
-    fn param_types() -> Box<[TypeId]>;
+    fn param_types() -> [TypeId; N];
+    /// Get the number of parameters for this function.
+    #[inline(always)]
+    #[must_use]
+    fn num_params() -> usize {
+        N
+    }
+    /// Is there a [`NativeCallContext`] parameter for this function?
+    #[inline(always)]
+    #[must_use]
+    fn has_context() -> bool {
+        X
+    }
     /// _(metadata)_ Get the type names of this function's parameters.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
     #[must_use]
-    fn param_names() -> Box<[&'static str]>;
+    fn param_names() -> [&'static str; N];
     /// _(metadata)_ Get the type ID of this function's return value.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
+    #[inline(always)]
     #[must_use]
-    fn return_type() -> TypeId;
+    fn return_type() -> TypeId {
+        if F {
+            TypeId::of::<RhaiResultOf<R>>()
+        } else {
+            TypeId::of::<R>()
+        }
+    }
     /// _(metadata)_ Get the type name of this function's return value.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
     #[inline(always)]
     #[must_use]
     fn return_type_name() -> &'static str {
-        std::any::type_name::<RET>()
+        type_name::<R>()
     }
 }
 
-const EXPECT_ARGS: &str = "arguments";
-
 macro_rules! check_constant {
-    ($abi:ident, $ctx:ident, $args:ident) => {
+    ($abi:ident, $n:expr, $fn_name:ident, $no_const:ident, $args:ident) => {
         #[cfg(any(not(feature = "no_object"), not(feature = "no_index")))]
-        if stringify!($abi) == "Method" && !$args.is_empty() {
-            let deny = match $args.len() {
-                #[cfg(not(feature = "no_index"))]
-                3 if $ctx.fn_name() == crate::engine::FN_IDX_SET && $args[0].is_read_only() => true,
-                #[cfg(not(feature = "no_object"))]
-                2 if $ctx.fn_name().starts_with(crate::engine::FN_SET)
-                    && $args[0].is_read_only() =>
-                {
-                    true
-                }
-                _ => false,
-            };
-
-            if deny {
+        if stringify!($abi) == "Method" && $no_const && $args[0].is_read_only() {
             return Err(crate::ERR::ErrorNonPureMethodCallOnConstant(
-                    $ctx.fn_name().to_string(),
+                $fn_name.to_string(),
                 crate::Position::NONE,
             )
             .into());
         }
-        }
     };
 }
 
 macro_rules! def_register {
     () => {
-        def_register!(imp Pure :);
+        def_register!(imp Pure : 0;);
     };
-    (imp $abi:ident : $($par:ident => $arg:expr => $mark:ty => $param:ty => $let:stmt => $clone:expr),*) => {
+    (imp $abi:ident : $n:expr ; $($par:ident => $arg:expr => $mark:ty => $param:ty => $clone:expr),*) => {
     //   ^ function ABI type
+    //                ^ number of parameters
     //                            ^ function parameter generic type name (A, B, C etc.)
     //                                          ^ call argument(like A, *B, &mut C etc)
     //                                                       ^ function parameter marker type (A, Ref<B> or Mut<C>)
     //                                                                   ^ function parameter actual type (A, &B or &mut C)
-    //                                                                      ^ argument let statement
+    //                                                                                ^ parameter access function (by_value or by_ref)
 
         impl<
             FN: Fn($($param),*) -> RET + SendSync + 'static,
             $($par: Variant + Clone,)*
-            RET: Variant + Clone
-        > RegisterNativeFunction<($($mark,)*), RET, ()> for FN {
-            #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RET>() }
-            #[inline(always)] fn into_callable_function(self) -> CallableFunction {
-                CallableFunction::$abi(Shared::new(move |_ctx: NativeCallContext, args: &mut FnCallArgs| {
+            RET: Variant + Clone,
+        > RegisterNativeFunction<($($mark,)*), $n, false, RET, false> for FN {
+            #[inline(always)] fn param_types() -> [TypeId;$n] { [$(TypeId::of::<$par>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> [&'static str;$n] { [$(type_name::<$param>()),*] }
+            #[inline(always)] fn into_callable_function(self, fn_name: Identifier, no_const: bool) -> CallableFunction {
+                CallableFunction::$abi(Shared::new(move |_, args: &mut FnCallArgs| {
                     // The arguments are assumed to be of the correct number and types!
-                    check_constant!($abi, _ctx, args);
+                    check_constant!($abi, $n, fn_name, no_const, args);
 
-                    let mut _drain = args.iter_mut();
-                    $($let $par = ($clone)(_drain.next().expect(EXPECT_ARGS)); )*
+                    let mut drain = args.iter_mut();
+                    $(let mut $par = $clone(drain.next().unwrap()); )*
 
                     // Call the function with each argument value
                     let r = self($($arg),*);
 
                     // Map the result
                     Ok(Dynamic::from(r))
-                }))
+                }), false)
             }
         }
 
         impl<
             FN: for<'a> Fn(NativeCallContext<'a>, $($param),*) -> RET + SendSync + 'static,
             $($par: Variant + Clone,)*
-            RET: Variant + Clone
-        > RegisterNativeFunction<($($mark,)*), RET, NativeCallContext<'static>> for FN {
-            #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RET>() }
-            #[inline(always)] fn into_callable_function(self) -> CallableFunction {
-                CallableFunction::$abi(Shared::new(move |ctx: NativeCallContext, args: &mut FnCallArgs| {
-                    // The arguments are assumed to be of the correct number and types!
-                    check_constant!($abi, ctx, args);
+            RET: Variant + Clone,
+        > RegisterNativeFunction<($($mark,)*), $n, true, RET, false> for FN {
+            #[inline(always)] fn param_types() -> [TypeId;$n] { [$(TypeId::of::<$par>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> [&'static str;$n] { [$(type_name::<$param>()),*] }
+            #[inline(always)] fn into_callable_function(self, fn_name: Identifier, no_const: bool) -> CallableFunction {
+                CallableFunction::$abi(Shared::new(move |ctx: Option<NativeCallContext>, args: &mut FnCallArgs| {
+                    let ctx = ctx.unwrap();
 
-                    let mut _drain = args.iter_mut();
-                    $($let $par = ($clone)(_drain.next().expect(EXPECT_ARGS)); )*
+                    // The arguments are assumed to be of the correct number and types!
+                    check_constant!($abi, $n, fn_name, no_const, args);
+
+                    let mut drain = args.iter_mut();
+                    $(let mut $par = $clone(drain.next().unwrap()); )*
 
                     // Call the function with each argument value
                     let r = self(ctx, $($arg),*);
 
                     // Map the result
                     Ok(Dynamic::from(r))
-                }))
+                }), true)
             }
         }
 
@@ -188,22 +208,21 @@ macro_rules! def_register {
             FN: Fn($($param),*) -> RhaiResultOf<RET> + SendSync + 'static,
             $($par: Variant + Clone,)*
             RET: Variant + Clone
-        > RegisterNativeFunction<($($mark,)*), RET, RhaiResultOf<()>> for FN {
-            #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RhaiResultOf<RET>>() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { std::any::type_name::<RhaiResultOf<RET>>() }
-            #[inline(always)] fn into_callable_function(self) -> CallableFunction {
-                CallableFunction::$abi(Shared::new(move |_ctx: NativeCallContext, args: &mut FnCallArgs| {
+        > RegisterNativeFunction<($($mark,)*), $n, false, RET, true> for FN {
+            #[inline(always)] fn param_types() -> [TypeId;$n] { [$(TypeId::of::<$par>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> [&'static str;$n] { [$(type_name::<$param>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { type_name::<RhaiResultOf<RET>>() }
+            #[inline(always)] fn into_callable_function(self, fn_name: Identifier, no_const: bool) -> CallableFunction {
+                CallableFunction::$abi(Shared::new(move |_, args: &mut FnCallArgs| {
                     // The arguments are assumed to be of the correct number and types!
-                    check_constant!($abi, _ctx, args);
+                    check_constant!($abi, $n, fn_name, no_const, args);
 
-                    let mut _drain = args.iter_mut();
-                    $($let $par = ($clone)(_drain.next().expect(EXPECT_ARGS)); )*
+                    let mut drain = args.iter_mut();
+                    $(let mut $par = $clone(drain.next().unwrap()); )*
 
                     // Call the function with each argument value
                     self($($arg),*).map(Dynamic::from)
-                }))
+                }), false)
             }
         }
 
@@ -211,40 +230,41 @@ macro_rules! def_register {
             FN: for<'a> Fn(NativeCallContext<'a>, $($param),*) -> RhaiResultOf<RET> + SendSync + 'static,
             $($par: Variant + Clone,)*
             RET: Variant + Clone
-        > RegisterNativeFunction<($($mark,)*), RET, RhaiResultOf<NativeCallContext<'static>>> for FN {
-            #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RhaiResultOf<RET>>() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { std::any::type_name::<RhaiResultOf<RET>>() }
-            #[inline(always)] fn into_callable_function(self) -> CallableFunction {
-                CallableFunction::$abi(Shared::new(move |ctx: NativeCallContext, args: &mut FnCallArgs| {
-                    // The arguments are assumed to be of the correct number and types!
-                    check_constant!($abi, ctx, args);
+        > RegisterNativeFunction<($($mark,)*), $n, true, RET, true> for FN {
+            #[inline(always)] fn param_types() -> [TypeId;$n] { [$(TypeId::of::<$par>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> [&'static str;$n] { [$(type_name::<$param>()),*] }
+            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { type_name::<RhaiResultOf<RET>>() }
+            #[inline(always)] fn into_callable_function(self, fn_name: Identifier, no_const: bool) -> CallableFunction {
+                CallableFunction::$abi(Shared::new(move |ctx: Option<NativeCallContext>, args: &mut FnCallArgs| {
+                    let ctx = ctx.unwrap();
 
-                    let mut _drain = args.iter_mut();
-                    $($let $par = ($clone)(_drain.next().expect(EXPECT_ARGS)); )*
+                    // The arguments are assumed to be of the correct number and types!
+                    check_constant!($abi, $n, fn_name, no_const, args);
+
+                    let mut drain = args.iter_mut();
+                    $(let mut $par = $clone(drain.next().unwrap()); )*
 
                     // Call the function with each argument value
                     self(ctx, $($arg),*).map(Dynamic::from)
-                }))
+                }), true)
             }
         }
 
         //def_register!(imp_pop $($par => $mark => $param),*);
     };
-    ($p0:ident $(, $p:ident)*) => {
-        def_register!(imp Pure   : $p0 => $p0      => $p0      => $p0      => let $p0     => by_value $(, $p => $p => $p => $p => let $p => by_value)*);
-        def_register!(imp Method : $p0 => &mut $p0 => Mut<$p0> => &mut $p0 => let mut $p0 => by_ref   $(, $p => $p => $p => $p => let $p => by_value)*);
+    ($p0:ident:$n0:expr $(, $p:ident: $n:expr)*) => {
+        def_register!(imp Pure   : $n0 ; $p0 => $p0      => $p0      => $p0      => by_value $(, $p => $p => $p => $p => by_value)*);
+        def_register!(imp Method : $n0 ; $p0 => &mut $p0 => Mut<$p0> => &mut $p0 => by_ref   $(, $p => $p => $p => $p => by_value)*);
         //                ^ CallableFunction constructor
-        //                                                             ^ first parameter passed through
+        //                         ^ number of arguments                            ^ first parameter passed through
         //                                                                                       ^ others passed by value (by_value)
 
         // Currently does not support first argument which is a reference, as there will be
         // conflicting implementations since &T: Any and T: Any cannot be distinguished
         //def_register!(imp $p0 => Ref<$p0> => &$p0     => by_ref   $(, $p => $p => $p => by_value)*);
 
-        def_register!($($p),*);
+        def_register!($($p: $n),*);
     };
 }
 
-def_register!(A, B, C, D, E, F, G, H, J, K, L, M, N, P, Q, R, S, T, U, V);
+def_register!(A:20, B:19, C:18, D:17, E:16, F:15, G:14, H:13, J:12, K:11, L:10, M:9, N:8, P:7, Q:6, R:5, S:4, T:3, U:2, V:1);

src/func/script.rs

@@ -4,7 +4,7 @@
 use super::call::FnCallArgs;
 use crate::ast::ScriptFnDef;
 use crate::eval::{Caches, GlobalRuntimeState};
-use crate::{Dynamic, Engine, Position, RhaiError, RhaiResult, Scope, ERR};
+use crate::{Dynamic, Engine, Position, RhaiResult, Scope, ERR};
 use std::mem;
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -33,32 +33,6 @@ impl Engine {
         rewind_scope: bool,
         pos: Position,
     ) -> RhaiResult {
-        #[cold]
-        #[inline(never)]
-        fn make_error(
-            name: String,
-            _fn_def: &ScriptFnDef,
-            global: &GlobalRuntimeState,
-            err: RhaiError,
-            pos: Position,
-        ) -> RhaiResult {
-            #[cfg(not(feature = "no_module"))]
-            let source = _fn_def
-                .environ
-                .as_ref()
-                .and_then(|environ| environ.lib.id().map(str::to_string));
-            #[cfg(feature = "no_module")]
-            let source = None;
-
-            Err(ERR::ErrorInFunctionCall(
-                name,
-                source.unwrap_or_else(|| global.source().unwrap_or("").to_string()),
-                err,
-                pos,
-            )
-            .into())
-        }
-
         assert!(fn_def.params.len() == args.len());
 
         self.track_operation(global, pos)?;
@@ -69,7 +43,7 @@ impl Engine {
         }
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_none() && fn_def.body.is_empty() {
+        if self.debugger_interface.is_none() && fn_def.body.is_empty() {
             return Ok(Dynamic::UNIT);
         }
         #[cfg(not(feature = "debugging"))]
@@ -96,15 +70,14 @@ impl Engine {
 
         // Push a new call stack frame
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
+            let fn_name = fn_def.name.clone();
+            let args = scope.iter().skip(orig_scope_len).map(|(.., v)| v).collect();
             let source = global.source.clone();
 
-            global.debugger_mut().push_call_stack_frame(
-                fn_def.name.clone(),
-                scope.iter().skip(orig_scope_len).map(|(.., v)| v).collect(),
-                source,
-                pos,
-            );
+            global
+                .debugger_mut()
+                .push_call_stack_frame(fn_name, args, source, pos);
         }
 
         // Merge in encapsulated environment, if any
@@ -131,37 +104,42 @@ impl Engine {
         };
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             let node = crate::ast::Stmt::Noop(fn_def.body.position());
             self.run_debugger(global, caches, scope, this_ptr, &node)?;
         }
 
         // Evaluate the function
-        let mut _result = self
+        let mut _result: RhaiResult = self
             .eval_stmt_block(global, caches, scope, this_ptr, &fn_def.body, rewind_scope)
             .or_else(|err| match *err {
                 // Convert return statement to return value
                 ERR::Return(x, ..) => Ok(x),
-                // Error in sub function call
-                ERR::ErrorInFunctionCall(name, src, err, ..) => {
-                    let fn_name = if src.is_empty() {
-                        format!("{name} < {}", fn_def.name)
-                    } else {
-                        format!("{name} @ '{src}' < {}", fn_def.name)
-                    };
-                    make_error(fn_name, fn_def, global, err, pos)
-                }
                 // System errors are passed straight-through
                 mut err if err.is_system_exception() => {
                     err.set_position(pos);
                     Err(err.into())
                 }
                 // Other errors are wrapped in `ErrorInFunctionCall`
-                _ => make_error(fn_def.name.to_string(), fn_def, global, err, pos),
+                _ => Err(ERR::ErrorInFunctionCall(
+                    fn_def.name.to_string(),
+                    #[cfg(not(feature = "no_module"))]
+                    fn_def
+                        .environ
+                        .as_deref()
+                        .and_then(|environ| environ.lib.id())
+                        .unwrap_or_else(|| global.source().unwrap_or(""))
+                        .to_string(),
+                    #[cfg(feature = "no_module")]
+                    global.source().unwrap_or("").to_string(),
+                    err,
+                    pos,
+                )
+                .into()),
             });
 
         #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
+        if self.is_debugger_registered() {
             let trigger = match global.debugger_mut().status {
                 crate::eval::DebuggerStatus::FunctionExit(n) => n >= global.level,
                 crate::eval::DebuggerStatus::Next(.., true) => true,
@@ -236,7 +214,9 @@ impl Engine {
             // Then check imported modules
             global.contains_qualified_fn(hash_script)
             // Then check sub-modules
-            || self.global_sub_modules.iter().flat_map(|m| m.values()).any(|m| m.contains_qualified_fn(hash_script));
+            || self.global_sub_modules.as_deref().map_or(false, |m| {
+                m.values().any(|m| m.contains_qualified_fn(hash_script))
+            });
 
         if !result && !cache.filter.is_absent_and_set(hash_script) {
             // Do not cache "one-hit wonders"

src/lib.rs

@@ -85,6 +85,11 @@ extern crate no_std_compat as std;
 use std::prelude::v1::*;
 
 // Internal modules
+#[macro_use]
+mod reify;
+#[macro_use]
+mod types;
+
 mod api;
 mod ast;
 pub mod config;
@@ -95,10 +100,8 @@ mod module;
 mod optimizer;
 pub mod packages;
 mod parser;
-mod reify;
 mod tests;
 mod tokenizer;
-mod types;
 
 /// Error encountered when parsing a script.
 type PERR = ParseErrorType;
@@ -207,9 +210,9 @@ pub use engine::{Engine, OP_CONTAINS, OP_EQUALS};
 pub use eval::EvalContext;
 pub use func::{NativeCallContext, RegisterNativeFunction};
 pub use module::{FnNamespace, Module};
-pub use tokenizer::Position;
 #[cfg(not(feature = "no_time"))]
 pub use types::Instant;
+pub use types::Position;
 pub use types::{
     Dynamic, EvalAltResult, FnPtr, ImmutableString, LexError, ParseError, ParseErrorType, Scope,
 };
@@ -311,12 +314,12 @@ pub use types::dynamic::{AccessMode, DynamicReadLock, DynamicWriteLock, Variant}
 pub use types::FloatWrapper;
 
 #[cfg(feature = "internals")]
-pub use types::StringsInterner;
+pub use types::{Span, StringsInterner};
 
 #[cfg(feature = "internals")]
 pub use tokenizer::{
     get_next_token, is_valid_function_name, is_valid_identifier, parse_string_literal, InputStream,
-    MultiInputsStream, Span, Token, TokenIterator, TokenizeState, TokenizerControl,
+    MultiInputsStream, Token, TokenIterator, TokenizeState, TokenizerControl,
     TokenizerControlBlock,
 };
 

src/module/mod.rs

@@ -9,8 +9,8 @@ use crate::func::{
 };
 use crate::types::{dynamic::Variant, BloomFilterU64, CustomTypesCollection};
 use crate::{
-    calc_fn_hash, calc_fn_hash_full, Dynamic, Identifier, ImmutableString, NativeCallContext,
-    RhaiResultOf, Shared, SharedModule, SmartString, StaticVec,
+    calc_fn_hash, calc_fn_hash_full, Dynamic, FnArgsVec, Identifier, ImmutableString,
+    NativeCallContext, RhaiResultOf, Shared, SharedModule, SmartString,
 };
 use bitflags::bitflags;
 #[cfg(feature = "no_std")]
@@ -72,20 +72,20 @@ pub struct FuncInfoMetadata {
     /// Function access mode.
     pub access: FnAccess,
     /// Function name.
-    pub name: ImmutableString,
+    pub name: Identifier,
     /// Number of parameters.
     pub num_params: usize,
     /// Parameter types (if applicable).
-    pub param_types: StaticVec<TypeId>,
+    pub param_types: FnArgsVec<TypeId>,
     /// Parameter names and types (if available).
     #[cfg(feature = "metadata")]
-    pub params_info: StaticVec<Identifier>,
+    pub params_info: FnArgsVec<Identifier>,
     /// Return type name.
     #[cfg(feature = "metadata")]
     pub return_type: Identifier,
     /// Comments.
     #[cfg(feature = "metadata")]
-    pub comments: Box<[Box<str>]>,
+    pub comments: Box<[Identifier]>,
 }
 
 /// A type containing a single registered function.
@@ -115,7 +115,7 @@ impl FuncInfo {
                 }
             }
         } else {
-            let params: StaticVec<_> = self
+            let params: FnArgsVec<_> = self
                 .metadata
                 .params_info
                 .iter()
@@ -231,7 +231,8 @@ impl fmt::Debug for Module {
                 "modules",
                 &self
                     .modules
-                    .iter()
+                    .as_deref()
+                    .into_iter()
                     .flat_map(|m| m.keys())
                     .map(SmartString::as_str)
                     .collect::<Vec<_>>(),
@@ -392,7 +393,7 @@ impl Module {
     #[inline]
     #[must_use]
     pub fn doc(&self) -> &str {
-        self.doc.as_ref().map_or("", |s| s.as_str())
+        self.doc.as_deref().map_or("", SmartString::as_str)
     }
 
     /// Set the documentation of the [`Module`].
@@ -542,16 +543,28 @@ impl Module {
     #[must_use]
     pub fn is_empty(&self) -> bool {
         !self.flags.contains(ModuleFlags::INDEXED_GLOBAL_FUNCTIONS)
-            && self.functions.as_ref().map_or(true, |m| m.is_empty())
-            && self.variables.as_ref().map_or(true, |m| m.is_empty())
-            && self.modules.as_ref().map_or(true, |m| m.is_empty())
-            && self.type_iterators.as_ref().map_or(true, |t| t.is_empty())
-            && self.all_functions.as_ref().map_or(true, |m| m.is_empty())
-            && self.all_variables.as_ref().map_or(true, |m| m.is_empty())
+            && self
+                .functions
+                .as_ref()
+                .map_or(true, StraightHashMap::is_empty)
+            && self.variables.as_deref().map_or(true, BTreeMap::is_empty)
+            && self.modules.as_deref().map_or(true, BTreeMap::is_empty)
+            && self
+                .type_iterators
+                .as_deref()
+                .map_or(true, BTreeMap::is_empty)
+            && self
+                .all_functions
+                .as_deref()
+                .map_or(true, StraightHashMap::is_empty)
+            && self
+                .all_variables
+                .as_deref()
+                .map_or(true, StraightHashMap::is_empty)
             && self
                 .all_type_iterators
-                .as_ref()
-                .map_or(true, |m| m.is_empty())
+                .as_deref()
+                .map_or(true, BTreeMap::is_empty)
     }
 
     /// Is the [`Module`] indexed?
@@ -710,7 +723,7 @@ impl Module {
                         namespace: FnNamespace::Internal,
                         access: fn_def.access,
                         num_params,
-                        param_types: StaticVec::new_const(),
+                        param_types: FnArgsVec::new_const(),
                         #[cfg(feature = "metadata")]
                         params_info,
                         #[cfg(feature = "metadata")]
@@ -866,16 +879,12 @@ impl Module {
     /// In other words, the number of entries should be one larger than the number of parameters.
     #[cfg(feature = "metadata")]
     #[inline]
-    pub fn update_fn_metadata<S: AsRef<str>>(
+    pub fn update_fn_metadata<S: Into<Identifier>>(
         &mut self,
         hash_fn: u64,
-        arg_names: impl AsRef<[S]>,
+        arg_names: impl IntoIterator<Item = S>,
     ) -> &mut Self {
-        let mut param_names: StaticVec<_> = arg_names
-            .as_ref()
-            .iter()
-            .map(|s| s.as_ref().into())
-            .collect();
+        let mut param_names: FnArgsVec<_> = arg_names.into_iter().map(Into::into).collect();
 
         if let Some(f) = self.functions.as_mut().and_then(|m| m.get_mut(&hash_fn)) {
             let (param_names, return_type_name) = if param_names.len() > f.metadata.num_params {
@@ -907,32 +916,30 @@ impl Module {
     ///
     /// ## Comments
     ///
-    /// Block doc-comments should be kept in a single line.
+    /// Block doc-comments should be kept in a separate string slice.
     ///
-    /// Line doc-comments should be kept in one string slice per line without the termination line-break.
+    /// Line doc-comments should be merged, with line-breaks, into a single string slice without a final termination line-break.
     ///
     /// Leading white-spaces should be stripped, and each string slice always starts with the corresponding
     /// doc-comment leader: `///` or `/**`.
+    ///
+    /// Each line in non-block doc-comments should start with `///`.
     #[cfg(feature = "metadata")]
     #[inline]
-    pub fn update_fn_metadata_with_comments<A: AsRef<str>, C: AsRef<str>>(
+    pub fn update_fn_metadata_with_comments<A: Into<Identifier>, C: Into<Identifier>>(
         &mut self,
         hash_fn: u64,
-        arg_names: impl AsRef<[A]>,
-        comments: impl AsRef<[C]>,
+        arg_names: impl IntoIterator<Item = A>,
+        comments: impl IntoIterator<Item = C>,
     ) -> &mut Self {
         self.update_fn_metadata(hash_fn, arg_names);
 
-        let comments = comments.as_ref();
-
-        if !comments.is_empty() {
-            let f = self
-                .functions
+        self.functions
             .as_mut()
             .and_then(|m| m.get_mut(&hash_fn))
-                .unwrap();
-            f.metadata.comments = comments.iter().map(|s| s.as_ref().into()).collect();
-        }
+            .unwrap()
+            .metadata
+            .comments = comments.into_iter().map(Into::into).collect();
 
         self
     }
@@ -997,12 +1004,11 @@ impl Module {
         let _arg_names = arg_names;
         let is_method = func.is_method();
 
-        let mut param_types: StaticVec<_> = arg_types
+        let mut param_types: FnArgsVec<_> = arg_types
             .as_ref()
             .iter()
-            .copied()
             .enumerate()
-            .map(|(i, type_id)| Self::map_type(!is_method || i > 0, type_id))
+            .map(|(i, &type_id)| Self::map_type(!is_method || i > 0, type_id))
             .collect();
         param_types.shrink_to_fit();
 
@@ -1013,11 +1019,11 @@ impl Module {
         #[cfg(feature = "metadata")]
         let (param_names, return_type_name) = {
             let mut names = _arg_names
-                .iter()
-                .flat_map(|&p| p.iter())
+                .into_iter()
+                .flatten()
                 .map(|&s| s.into())
-                .collect::<StaticVec<_>>();
-            let return_type = if names.len() > arg_types.as_ref().len() {
+                .collect::<FnArgsVec<_>>();
+            let return_type = if names.len() > param_types.len() {
                 names.pop().unwrap()
             } else {
                 crate::SmartString::new_const()
@@ -1086,12 +1092,14 @@ impl Module {
     ///
     /// ## Comments
     ///
-    /// Block doc-comments should be kept in a single line.
+    /// Block doc-comments should be kept in a separate string slice.
     ///
-    /// Line doc-comments should be kept in one string slice per line without the termination line-break.
+    /// Line doc-comments should be merged, with line-breaks, into a single string slice without a final termination line-break.
     ///
     /// Leading white-spaces should be stripped, and each string slice always starts with the corresponding
     /// doc-comment leader: `///` or `/**`.
+    ///
+    /// Each line in non-block doc-comments should start with `///`.
     #[cfg(feature = "metadata")]
     #[inline]
     pub fn set_fn_with_comments<S: AsRef<str>>(
@@ -1101,17 +1109,18 @@ impl Module {
         access: FnAccess,
         arg_names: Option<&[&str]>,
         arg_types: impl AsRef<[TypeId]>,
-        comments: impl AsRef<[S]>,
+        comments: impl IntoIterator<Item = S>,
         func: CallableFunction,
     ) -> u64 {
         let hash = self.set_fn(name, namespace, access, arg_names, arg_types, func);
 
-        let comments = comments.as_ref();
-
-        if !comments.is_empty() {
-            let f = self.functions.as_mut().unwrap().get_mut(&hash).unwrap();
-            f.metadata.comments = comments.iter().map(|s| s.as_ref().into()).collect();
-        }
+        self.functions
+            .as_mut()
+            .unwrap()
+            .get_mut(&hash)
+            .unwrap()
+            .metadata
+            .comments = comments.into_iter().map(|s| s.as_ref().into()).collect();
 
         hash
     }
@@ -1191,8 +1200,9 @@ impl Module {
         arg_types: impl AsRef<[TypeId]>,
         func: impl Fn(NativeCallContext, &mut FnCallArgs) -> RhaiResultOf<T> + SendSync + 'static,
     ) -> u64 {
-        let f =
-            move |ctx: NativeCallContext, args: &mut FnCallArgs| func(ctx, args).map(Dynamic::from);
+        let f = move |ctx: Option<NativeCallContext>, args: &mut FnCallArgs| {
+            func(ctx.unwrap(), args).map(Dynamic::from)
+        };
 
         self.set_fn(
             name,
@@ -1200,7 +1210,7 @@ impl Module {
             access,
             None,
             arg_types,
-            CallableFunction::Method(Shared::new(f)),
+            CallableFunction::Method(Shared::new(f), true),
         )
     }
 
@@ -1227,22 +1237,33 @@ impl Module {
     /// assert!(module.contains_fn(hash));
     /// ```
     #[inline(always)]
-    pub fn set_native_fn<A, T, F, S>(
+    pub fn set_native_fn<A: 'static, const N: usize, const C: bool, T, F>(
         &mut self,
         name: impl AsRef<str> + Into<Identifier>,
         func: F,
     ) -> u64
     where
         T: Variant + Clone,
-        F: RegisterNativeFunction<A, T, RhaiResultOf<S>>,
+        F: RegisterNativeFunction<A, N, C, T, true>,
     {
+        let fn_name = name.into();
+        let no_const = false;
+
+        #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
+        let no_const = no_const || (F::num_params() == 3 && fn_name == crate::engine::FN_IDX_SET);
+        #[cfg(not(feature = "no_object"))]
+        let no_const =
+            no_const || (F::num_params() == 2 && fn_name.starts_with(crate::engine::FN_SET));
+
+        let func = func.into_callable_function(fn_name.clone(), no_const);
+
         self.set_fn(
-            name,
+            fn_name,
             FnNamespace::Internal,
             FnAccess::Public,
             None,
-            &F::param_types(),
-            func.into_callable_function(),
+            F::param_types(),
+            func,
         )
     }
 
@@ -1266,19 +1287,22 @@ impl Module {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn set_getter_fn<A, T, F, S>(&mut self, name: impl AsRef<str>, func: F) -> u64
+    pub fn set_getter_fn<A, const C: bool, T, F>(&mut self, name: impl AsRef<str>, func: F) -> u64
     where
         A: Variant + Clone,
         T: Variant + Clone,
-        F: RegisterNativeFunction<(Mut<A>,), T, RhaiResultOf<S>> + SendSync + 'static,
+        F: RegisterNativeFunction<(Mut<A>,), 1, C, T, true> + SendSync + 'static,
     {
+        let fn_name = crate::engine::make_getter(name.as_ref());
+        let func = func.into_callable_function(fn_name.clone(), false);
+
         self.set_fn(
-            crate::engine::make_getter(name.as_ref()).as_str(),
+            fn_name,
             FnNamespace::Global,
             FnAccess::Public,
             None,
-            &F::param_types(),
-            func.into_callable_function(),
+            F::param_types(),
+            func,
         )
     }
 
@@ -1307,19 +1331,22 @@ impl Module {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn set_setter_fn<A, T, F, S>(&mut self, name: impl AsRef<str>, func: F) -> u64
+    pub fn set_setter_fn<A, const C: bool, T, F>(&mut self, name: impl AsRef<str>, func: F) -> u64
     where
         A: Variant + Clone,
         T: Variant + Clone,
-        F: RegisterNativeFunction<(Mut<A>, T), (), RhaiResultOf<S>> + SendSync + 'static,
+        F: RegisterNativeFunction<(Mut<A>, T), 2, C, (), true> + SendSync + 'static,
     {
+        let fn_name = crate::engine::make_setter(name.as_ref());
+        let func = func.into_callable_function(fn_name.clone(), true);
+
         self.set_fn(
-            crate::engine::make_setter(name.as_ref()).as_str(),
+            fn_name,
             FnNamespace::Global,
             FnAccess::Public,
             None,
-            &F::param_types(),
-            func.into_callable_function(),
+            F::param_types(),
+            func,
         )
     }
 
@@ -1353,11 +1380,16 @@ impl Module {
     /// ```
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    pub fn set_getter_setter_fn<A: Variant + Clone, T: Variant + Clone, S1, S2>(
+    pub fn set_getter_setter_fn<
+        A: Variant + Clone,
+        const C1: bool,
+        const C2: bool,
+        T: Variant + Clone,
+    >(
         &mut self,
         name: impl AsRef<str>,
-        getter: impl RegisterNativeFunction<(Mut<A>,), T, RhaiResultOf<S1>> + SendSync + 'static,
-        setter: impl RegisterNativeFunction<(Mut<A>, T), (), RhaiResultOf<S2>> + SendSync + 'static,
+        getter: impl RegisterNativeFunction<(Mut<A>,), 1, C1, T, true> + SendSync + 'static,
+        setter: impl RegisterNativeFunction<(Mut<A>, T), 2, C2, (), true> + SendSync + 'static,
     ) -> (u64, u64) {
         (
             self.set_getter_fn(name.as_ref(), getter),
@@ -1394,12 +1426,12 @@ impl Module {
     /// ```
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline]
-    pub fn set_indexer_get_fn<A, B, T, F, S>(&mut self, func: F) -> u64
+    pub fn set_indexer_get_fn<A, B, const C: bool, T, F>(&mut self, func: F) -> u64
     where
         A: Variant + Clone,
         B: Variant + Clone,
         T: Variant + Clone,
-        F: RegisterNativeFunction<(Mut<A>, B), T, RhaiResultOf<S>> + SendSync + 'static,
+        F: RegisterNativeFunction<(Mut<A>, B), 2, C, T, true> + SendSync + 'static,
     {
         #[cfg(not(feature = "no_index"))]
         if TypeId::of::<A>() == TypeId::of::<crate::Array>() {
@@ -1421,8 +1453,8 @@ impl Module {
             FnNamespace::Global,
             FnAccess::Public,
             None,
-            &F::param_types(),
-            func.into_callable_function(),
+            F::param_types(),
+            func.into_callable_function(crate::engine::FN_IDX_GET.into(), false),
         )
     }
 
@@ -1455,12 +1487,12 @@ impl Module {
     /// ```
     #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
     #[inline]
-    pub fn set_indexer_set_fn<A, B, T, F, S>(&mut self, func: F) -> u64
+    pub fn set_indexer_set_fn<A, B, const C: bool, T, F>(&mut self, func: F) -> u64
     where
         A: Variant + Clone,
         B: Variant + Clone,
         T: Variant + Clone,
-        F: RegisterNativeFunction<(Mut<A>, B, T), (), RhaiResultOf<S>> + SendSync + 'static,
+        F: RegisterNativeFunction<(Mut<A>, B, T), 3, C, (), true> + SendSync + 'static,
     {
         #[cfg(not(feature = "no_index"))]
         if TypeId::of::<A>() == TypeId::of::<crate::Array>() {
@@ -1482,8 +1514,8 @@ impl Module {
             FnNamespace::Global,
             FnAccess::Public,
             None,
-            &F::param_types(),
-            func.into_callable_function(),
+            F::param_types(),
+            func.into_callable_function(crate::engine::FN_IDX_SET.into(), true),
         )
     }
 
@@ -1527,13 +1559,13 @@ impl Module {
     pub fn set_indexer_get_set_fn<
         A: Variant + Clone,
         B: Variant + Clone,
+        const C1: bool,
+        const C2: bool,
         T: Variant + Clone,
-        S1,
-        S2,
     >(
         &mut self,
-        get_fn: impl RegisterNativeFunction<(Mut<A>, B), T, RhaiResultOf<S1>> + SendSync + 'static,
-        set_fn: impl RegisterNativeFunction<(Mut<A>, B, T), (), RhaiResultOf<S2>> + SendSync + 'static,
+        get_fn: impl RegisterNativeFunction<(Mut<A>, B), 2, C1, T, true> + SendSync + 'static,
+        set_fn: impl RegisterNativeFunction<(Mut<A>, B, T), 3, C2, (), true> + SendSync + 'static,
     ) -> (u64, u64) {
         (
             self.set_indexer_get_fn(get_fn),
@@ -1633,8 +1665,8 @@ impl Module {
         self.flags &= !ModuleFlags::INDEXED & !ModuleFlags::INDEXED_GLOBAL_FUNCTIONS;
 
         #[cfg(feature = "metadata")]
-        if !other.doc.as_ref().map_or(true, |s| s.is_empty()) {
-            if !self.doc.as_ref().map_or(true, |s| s.is_empty()) {
+        if !other.doc.as_deref().map_or(true, SmartString::is_empty) {
+            if !self.doc.as_deref().map_or(true, SmartString::is_empty) {
                 self.doc.get_or_insert_with(Default::default).push('\n');
             }
             self.doc
@@ -1689,8 +1721,8 @@ impl Module {
         self.flags &= !ModuleFlags::INDEXED & !ModuleFlags::INDEXED_GLOBAL_FUNCTIONS;
 
         #[cfg(feature = "metadata")]
-        if !other.doc.as_ref().map_or(true, |s| s.is_empty()) {
-            if !self.doc.as_ref().map_or(true, |s| s.is_empty()) {
+        if !other.doc.as_deref().map_or(true, SmartString::is_empty) {
+            if !self.doc.as_deref().map_or(true, SmartString::is_empty) {
                 self.doc.get_or_insert_with(Default::default).push('\n');
             }
             self.doc
@@ -1754,8 +1786,8 @@ impl Module {
         self.flags &= !ModuleFlags::INDEXED & !ModuleFlags::INDEXED_GLOBAL_FUNCTIONS;
 
         #[cfg(feature = "metadata")]
-        if !other.doc.as_ref().map_or(true, |s| s.is_empty()) {
-            if !self.doc.as_ref().map_or(true, |s| s.is_empty()) {
+        if !other.doc.as_deref().map_or(true, SmartString::is_empty) {
+            if !self.doc.as_deref().map_or(true, SmartString::is_empty) {
                 self.doc.get_or_insert_with(Default::default).push('\n');
             }
             self.doc
@@ -1837,8 +1869,8 @@ impl Module {
         self.flags &= !ModuleFlags::INDEXED & !ModuleFlags::INDEXED_GLOBAL_FUNCTIONS;
 
         #[cfg(feature = "metadata")]
-        if !other.doc.as_ref().map_or(true, |s| s.is_empty()) {
-            if !self.doc.as_ref().map_or(true, |s| s.is_empty()) {
+        if !other.doc.as_deref().map_or(true, SmartString::is_empty) {
+            if !self.doc.as_deref().map_or(true, SmartString::is_empty) {
                 self.doc.get_or_insert_with(Default::default).push('\n');
             }
             self.doc
@@ -1886,9 +1918,9 @@ impl Module {
     #[must_use]
     pub fn count(&self) -> (usize, usize, usize) {
         (
-            self.variables.as_ref().map_or(0, |m| m.len()),
-            self.functions.as_ref().map_or(0, |m| m.len()),
-            self.type_iterators.as_ref().map_or(0, |t| t.len()),
+            self.variables.as_deref().map_or(0, BTreeMap::len),
+            self.functions.as_ref().map_or(0, StraightHashMap::len),
+            self.type_iterators.as_deref().map_or(0, BTreeMap::len),
         )
     }
 
@@ -1896,16 +1928,20 @@ impl Module {
     #[inline]
     pub fn iter_sub_modules(&self) -> impl Iterator<Item = (&str, &SharedModule)> {
         self.modules
-            .iter()
-            .flat_map(|m| m.iter().map(|(k, m)| (k.as_str(), m)))
+            .as_deref()
+            .into_iter()
+            .flatten()
+            .map(|(k, m)| (k.as_str(), m))
     }
 
     /// Get an iterator to the variables in the [`Module`].
     #[inline]
     pub fn iter_var(&self) -> impl Iterator<Item = (&str, &Dynamic)> {
         self.variables
-            .iter()
-            .flat_map(|m| m.iter().map(|(k, v)| (k.as_str(), v)))
+            .as_deref()
+            .into_iter()
+            .flatten()
+            .map(|(k, v)| (k.as_str(), v))
     }
 
     /// Get an iterator to the functions in the [`Module`].
@@ -2065,7 +2101,7 @@ impl Module {
         let mut module = Module::new();
 
         // Extra modules left become sub-modules
-        let mut imports = StaticVec::new_const();
+        let mut imports = crate::StaticVec::new_const();
 
         if result.is_ok() {
             global
@@ -2088,7 +2124,8 @@ impl Module {
 
         global.source = orig_source;
 
-        result?;
+        // The return value is thrown away and not used
+        let _ = result?;
 
         // Variables with an alias left in the scope become module variables
         for (_name, value, mut aliases) in scope {
@@ -2223,7 +2260,7 @@ impl Module {
             }
 
             // Index all Rust functions
-            for (&hash, f) in module.functions.iter().flat_map(|m| m.iter()) {
+            for (&hash, f) in module.functions.iter().flatten() {
                 match f.metadata.namespace {
                     FnNamespace::Global => {
                         // Flatten all functions with global namespace
@@ -2260,11 +2297,11 @@ impl Module {
         if !self.is_indexed() {
             let mut path = Vec::with_capacity(4);
             let mut variables = StraightHashMap::with_capacity_and_hasher(
-                self.variables.as_ref().map_or(0, |m| m.len()),
+                self.variables.as_deref().map_or(0, BTreeMap::len),
                 Default::default(),
             );
             let mut functions = StraightHashMap::with_capacity_and_hasher(
-                self.functions.as_ref().map_or(0, |m| m.len()),
+                self.functions.as_ref().map_or(0, StraightHashMap::len),
                 Default::default(),
             );
             let mut type_iterators = BTreeMap::new();

src/module/resolvers/file.rs

@@ -170,7 +170,7 @@ impl FileModuleResolver {
     #[inline(always)]
     #[must_use]
     pub fn base_path(&self) -> Option<&Path> {
-        self.base_path.as_ref().map(<_>::as_ref)
+        self.base_path.as_deref()
     }
     /// Set the base path for script files.
     #[inline(always)]

src/optimizer.rs

@@ -24,6 +24,9 @@ use std::{
     mem,
 };
 
+/// Standard not operator.
+const OP_NOT: &str = Token::Bang.literal_syntax();
+
 /// Level of optimization performed.
 #[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
 #[non_exhaustive]
@@ -65,18 +68,19 @@ struct OptimizerState<'a> {
 }
 
 impl<'a> OptimizerState<'a> {
-    /// Create a new State.
+    /// Create a new [`OptimizerState`].
     #[inline(always)]
     pub fn new(
         engine: &'a Engine,
-        #[cfg(not(feature = "no_function"))] lib: &'a [crate::SharedModule],
+        lib: &'a [crate::SharedModule],
         optimization_level: OptimizationLevel,
     ) -> Self {
         let mut _global = GlobalRuntimeState::new(engine);
+        let _lib = lib;
 
         #[cfg(not(feature = "no_function"))]
         {
-            _global.lib = lib.iter().cloned().collect();
+            _global.lib = _lib.iter().cloned().collect();
         }
 
         Self {
@@ -138,7 +142,7 @@ impl<'a> OptimizerState<'a> {
     pub fn call_fn_with_constant_arguments(
         &mut self,
         fn_name: &str,
-        op_token: Option<&Token>,
+        op_token: Token,
         arg_values: &mut [Dynamic],
     ) -> Dynamic {
         self.engine
@@ -156,39 +160,6 @@ impl<'a> OptimizerState<'a> {
     }
 }
 
-// Has a system function a Rust-native override?
-fn has_native_fn_override(
-    engine: &Engine,
-    hash_script: u64,
-    arg_types: impl AsRef<[TypeId]>,
-) -> bool {
-    let hash = calc_fn_hash_full(hash_script, arg_types.as_ref().iter().copied());
-
-    // First check the global namespace and packages, but skip modules that are standard because
-    // they should never conflict with system functions.
-    if engine
-        .global_modules
-        .iter()
-        .filter(|m| !m.flags.contains(ModuleFlags::STANDARD_LIB))
-        .any(|m| m.contains_fn(hash))
-    {
-        return true;
-    }
-
-    // Then check sub-modules
-    #[cfg(not(feature = "no_module"))]
-    if engine
-        .global_sub_modules
-        .iter()
-        .flat_map(|m| m.values())
-        .any(|m| m.contains_qualified_fn(hash))
-    {
-        return true;
-    }
-
-    false
-}
-
 /// Optimize a block of [statements][Stmt].
 fn optimize_stmt_block(
     mut statements: StmtBlockContainer,
@@ -1019,7 +990,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
         // ``
         Expr::InterpolatedString(x, pos) if x.is_empty() => {
             state.set_dirty();
-            *expr = Expr::StringConstant(state.engine.get_interned_string(""), *pos);
+            *expr = Expr::StringConstant(state.engine.const_empty_string(), *pos);
         }
         // `... ${const} ...`
         Expr::InterpolatedString(..) if expr.is_constant() => {
@@ -1097,6 +1068,20 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
             *expr = mem::take(&mut x.lhs);
         },
 
+        // !true or !false
+        Expr::FnCall(x,..)
+            if x.name == OP_NOT
+            && x.args.len() == 1
+            && matches!(x.args[0], Expr::BoolConstant(..))
+        => {
+            state.set_dirty();
+            if let Expr::BoolConstant(b, pos) = x.args[0] {
+                *expr = Expr::BoolConstant(!b, pos)
+            } else {
+                unreachable!()
+            }
+        }
+
         // eval!
         Expr::FnCall(x, ..) if x.name == KEYWORD_EVAL => {
             state.propagate_constants = false;
@@ -1150,10 +1135,14 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                     return;
                 }
                 // Overloaded operators can override built-in.
-                _ if x.args.len() == 2 && x.op_token.is_some() && (state.engine.fast_operators() || !has_native_fn_override(state.engine, x.hashes.native(), &arg_types)) => {
-                    if let Some(result) = get_builtin_binary_op_fn(x.op_token.as_ref().unwrap(), &arg_values[0], &arg_values[1])
-                        .and_then(|f| {
-                            let context = (state.engine, x.name.as_str(),None, &state.global, *pos).into();
+                _ if x.args.len() == 2 && x.op_token != Token::NONE && (state.engine.fast_operators() || !state.engine.has_native_fn_override(x.hashes.native(), &arg_types)) => {
+                    if let Some(result) = get_builtin_binary_op_fn(x.op_token.clone(), &arg_values[0], &arg_values[1])
+                        .and_then(|(f, ctx)| {
+                            let context = if ctx {
+                                Some((state.engine, x.name.as_str(),None, &state.global, *pos).into())
+                            } else {
+                                None
+                            };
                             let (first, second) = arg_values.split_first_mut().unwrap();
                             (f)(context, &mut [ first, &mut second[0] ]).ok()
                         }) {
@@ -1204,7 +1193,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                     KEYWORD_TYPE_OF if arg_values.len() == 1 => state.engine.map_type_name(arg_values[0].type_name()).into(),
                     #[cfg(not(feature = "no_closure"))]
                     crate::engine::KEYWORD_IS_SHARED if arg_values.len() == 1 => Dynamic::FALSE,
-                    _ => state.call_fn_with_constant_arguments(&x.name, x.op_token.as_ref(), arg_values)
+                    _ => state.call_fn_with_constant_arguments(&x.name, x.op_token.clone(), arg_values)
                 };
 
                 if !result.is_null() {
@@ -1260,14 +1249,45 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
     }
 }
 
+impl Engine {
+    /// Has a system function a Rust-native override?
+    fn has_native_fn_override(&self, hash_script: u64, arg_types: impl AsRef<[TypeId]>) -> bool {
+        let hash = calc_fn_hash_full(hash_script, arg_types.as_ref().iter().copied());
+
+        // First check the global namespace and packages, but skip modules that are standard because
+        // they should never conflict with system functions.
+        if self
+            .global_modules
+            .iter()
+            .filter(|m| !m.flags.contains(ModuleFlags::STANDARD_LIB))
+            .any(|m| m.contains_fn(hash))
+        {
+            return true;
+        }
+
+        // Then check sub-modules
+        #[cfg(not(feature = "no_module"))]
+        if self
+            .global_sub_modules
+            .as_deref()
+            .into_iter()
+            .flatten()
+            .any(|(_, m)| m.contains_qualified_fn(hash))
+        {
+            return true;
+        }
+
+        false
+    }
+
     /// Optimize a block of [statements][Stmt] at top level.
     ///
     /// Constants and variables from the scope are added.
     fn optimize_top_level(
+        &self,
         statements: StmtBlockContainer,
-    engine: &Engine,
         scope: &Scope,
-    #[cfg(not(feature = "no_function"))] lib: &[crate::SharedModule],
+        lib: &[crate::SharedModule],
         optimization_level: OptimizationLevel,
     ) -> StmtBlockContainer {
         let mut statements = statements;
@@ -1279,20 +1299,10 @@ fn optimize_top_level(
         }
 
         // Set up the state
-    let mut state = OptimizerState::new(
-        engine,
-        #[cfg(not(feature = "no_function"))]
-        lib,
-        optimization_level,
-    );
+        let mut state = OptimizerState::new(self, lib, optimization_level);
 
         // Add constants from global modules
-    for (name, value) in engine
-        .global_modules
-        .iter()
-        .rev()
-        .flat_map(|m| m.iter_var())
-    {
+        for (name, value) in self.global_modules.iter().rev().flat_map(|m| m.iter_var()) {
             state.push_var(name, AccessMode::ReadOnly, value.clone());
         }
 
@@ -1308,9 +1318,9 @@ fn optimize_top_level(
         optimize_stmt_block(statements, &mut state, true, false, true)
     }
 
-/// Optimize an [`AST`].
-pub fn optimize_into_ast(
-    engine: &Engine,
+    /// Optimize a collection of statements and functions into an [`AST`].
+    pub(crate) fn optimize_into_ast(
+        &self,
         scope: &Scope,
         statements: StmtBlockContainer,
         #[cfg(not(feature = "no_function"))] functions: StaticVec<
@@ -1350,7 +1360,7 @@ pub fn optimize_into_ast(
                     // Optimize the function body
                     let body = mem::take(&mut *fn_def.body);
 
-                *fn_def.body = optimize_top_level(body, engine, scope, lib2, optimization_level);
+                    *fn_def.body = self.optimize_top_level(body, scope, lib2, optimization_level);
 
                     module.set_script_fn(fn_def);
                 }
@@ -1362,22 +1372,20 @@ pub fn optimize_into_ast(
 
             module.into()
         };
+        #[cfg(feature = "no_function")]
+        let lib: crate::Shared<_> = crate::Module::new().into();
 
         statements.shrink_to_fit();
 
         AST::new(
             match optimization_level {
                 OptimizationLevel::None => statements,
-            OptimizationLevel::Simple | OptimizationLevel::Full => optimize_top_level(
-                statements,
-                engine,
-                scope,
-                #[cfg(not(feature = "no_function"))]
-                &[lib.clone()],
-                optimization_level,
-            ),
+                OptimizationLevel::Simple | OptimizationLevel::Full => {
+                    self.optimize_top_level(statements, scope, &[lib.clone()], optimization_level)
+                }
             },
             #[cfg(not(feature = "no_function"))]
             lib,
         )
     }
+}

src/packages/array_basic.rs

@@ -261,8 +261,7 @@ pub mod array_functions {
                         m1 += m2;
                         s1 += s2;
 
-                        _ctx.engine()
-                            .raise_err_if_over_data_size_limit((a1, m1, s1))?;
+                        _ctx.engine().throw_on_size((a1, m1, s1))?;
 
                         guard.push(item.clone());
                         arr_len += 1;

src/packages/blob_basic.rs

@@ -81,8 +81,7 @@ pub mod blob_functions {
 
         // Check if blob will be over max size limit
         #[cfg(not(feature = "unchecked"))]
-        _ctx.engine()
-            .raise_err_if_over_data_size_limit((len, 0, 0))?;
+        _ctx.engine().throw_on_size((len, 0, 0))?;
 
         let mut blob = Blob::new();
         blob.resize(len, (value & 0x0000_00ff) as u8);

src/packages/iter_basic.rs

@@ -235,18 +235,18 @@ macro_rules! reg_range {
                     concat!("from: ", stringify!($y)),
                     concat!("to: ", stringify!($y)),
                     concat!("Iterator<", stringify!($y), ">"),
-            ], [
-                "/// Return an iterator over the exclusive range of `from..to`.",
-                "/// The value `to` is never included.",
-                "///",
-                "/// # Example",
-                "///",
-                "/// ```rhai",
-                "/// // prints all values from 8 to 17",
-                "/// for n in range(8, 18) {",
-                "///     print(n);",
-                "/// }",
-                "/// ```"
+            ], ["\
+                /// Return an iterator over the exclusive range of `from..to`.\n\
+                /// The value `to` is never included.\n\
+                ///\n\
+                /// # Example\n\
+                ///\n\
+                /// ```rhai\n\
+                /// // prints all values from 8 to 17\n\
+                /// for n in range(8, 18) {\n\
+                ///     print(n);\n\
+                /// }\n\
+                /// ```"
             ]);
 
             $lib.set_iterator::<RangeInclusive<$y>>();
@@ -269,27 +269,27 @@ macro_rules! reg_range {
                     concat!("to: ", stringify!($y)),
                     concat!("step: ", stringify!($y)),
                     concat!("Iterator<", stringify!($y), ">")
-            ], [
-                "/// Return an iterator over the exclusive range of `from..to`, each iteration increasing by `step`.",
-                "/// The value `to` is never included.",
-                "///",
-                "/// If `from` > `to` and `step` < 0, iteration goes backwards.",
-                "///",
-                "/// If `from` > `to` and `step` > 0 or `from` < `to` and `step` < 0, an empty iterator is returned.",
-                "///",
-                "/// # Example",
-                "///",
-                "/// ```rhai",
-                "/// // prints all values from 8 to 17 in steps of 3",
-                "/// for n in range(8, 18, 3) {",
-                "///     print(n);",
-                "/// }",
-                "///",
-                "/// // prints all values down from 18 to 9 in steps of -3",
-                "/// for n in range(18, 8, -3) {",
-                "///     print(n);",
-                "/// }",
-                "/// ```"
+            ], ["\
+                /// Return an iterator over the exclusive range of `from..to`, each iteration increasing by `step`.\n\
+                /// The value `to` is never included.\n\
+                ///\n\
+                /// If `from` > `to` and `step` < 0, iteration goes backwards.\n\
+                ///\n\
+                /// If `from` > `to` and `step` > 0 or `from` < `to` and `step` < 0, an empty iterator is returned.\n\
+                ///\n\
+                /// # Example\n\
+                ///\n\
+                /// ```rhai\n\
+                /// // prints all values from 8 to 17 in steps of 3\n\
+                /// for n in range(8, 18, 3) {\n\
+                ///     print(n);\n\
+                /// }\n\
+                ///\n\
+                /// // prints all values down from 18 to 9 in steps of -3\n\
+                /// for n in range(18, 8, -3) {\n\
+                ///     print(n);\n\
+                /// }\n\
+                /// ```"
             ]);
 
             let _hash = $lib.set_native_fn($x, |range: std::ops::Range<$y>, step: $y| StepRange::new(range.start, range.end, step, $add));
@@ -299,26 +299,26 @@ macro_rules! reg_range {
                     concat!("range: Range<", stringify!($y), ">"),
                     concat!("step: ", stringify!($y)),
                     concat!("Iterator<", stringify!($y), ">")
-            ], [
-                "/// Return an iterator over an exclusive range, each iteration increasing by `step`.",
-                "///",
-                "/// If `range` is reversed and `step` < 0, iteration goes backwards.",
-                "///",
-                "/// Otherwise, if `range` is empty, an empty iterator is returned.",
-                "///",
-                "/// # Example",
-                "///",
-                "/// ```rhai",
-                "/// // prints all values from 8 to 17 in steps of 3",
-                "/// for n in range(8..18, 3) {",
-                "///     print(n);",
-                "/// }",
-                "///",
-                "/// // prints all values down from 18 to 9 in steps of -3",
-                "/// for n in range(18..8, -3) {",
-                "///     print(n);",
-                "/// }",
-                "/// ```"
+            ], ["\
+                /// Return an iterator over an exclusive range, each iteration increasing by `step`.\n\
+                ///\n\
+                /// If `range` is reversed and `step` < 0, iteration goes backwards.\n\
+                ///\n\
+                /// Otherwise, if `range` is empty, an empty iterator is returned.\n\
+                ///\n\
+                /// # Example\n\
+                ///\n\
+                /// ```rhai\n\
+                /// // prints all values from 8 to 17 in steps of 3\n\
+                /// for n in range(8..18, 3) {\n\
+                ///     print(n);\n\
+                /// }\n\
+                ///\n\
+                /// // prints all values down from 18 to 9 in steps of -3\n\
+                /// for n in range(18..8, -3) {\n\
+                ///     print(n);\n\
+                /// }\n\
+                /// ```"
             ]);
         )*
     };
@@ -665,6 +665,7 @@ mod range_functions {
     }
     /// Return true if the range contains no items.
     #[rhai_fn(get = "is_empty", name = "is_empty", pure)]
+    #[allow(unstable_name_collisions)]
     pub fn is_empty_exclusive(range: &mut ExclusiveRange) -> bool {
         range.is_empty()
     }

src/packages/lang_core.rs

@@ -220,7 +220,7 @@ fn collect_fn_metadata(
                 "comments".into(),
                 func.comments
                     .iter()
-                    .map(|s| engine.get_interned_string(s.as_ref()).into())
+                    .map(|s| engine.get_interned_string(s.as_str()).into())
                     .collect::<Array>()
                     .into(),
             );
@@ -267,9 +267,10 @@ fn collect_fn_metadata(
     #[cfg(not(feature = "no_module"))]
     ctx.engine()
         .global_sub_modules
-        .iter()
-        .flat_map(|m| m.values())
-        .flat_map(|m| m.iter_script_fn())
+        .as_deref()
+        .into_iter()
+        .flatten()
+        .flat_map(|(_, m)| m.iter_script_fn())
         .filter(|(ns, a, n, p, f)| filter(*ns, *a, n, *p, f))
         .for_each(|(.., f)| {
             list.push(

src/reify.rs

@@ -8,7 +8,6 @@
 /// * `reify!(`_variable_ or _expression_`,|`_temp-variable_`: `_type_`|` _code_ `)`
 /// * `reify!(`_variable_ or _expression_ `=>` `Option<`_type_`>` `)`
 /// * `reify!(`_variable_ or _expression_ `=>` _type_ `)`
-#[macro_export]
 macro_rules! reify {
     ($old:ident, |$new:ident : $t:ty| $code:expr, || $fallback:expr) => {{
         #[allow(clippy::redundant_else)]

src/serde/metadata.rs

@@ -168,10 +168,12 @@ pub fn gen_metadata_to_json(
     include_standard_packages: bool,
 ) -> serde_json::Result<String> {
     let _ast = ast;
+    #[cfg(feature = "metadata")]
+    let mut global_doc = String::new();
     let mut global = ModuleMetadata::new();
 
     #[cfg(not(feature = "no_module"))]
-    for (name, m) in engine.global_sub_modules.iter().flat_map(|m| m.iter()) {
+    for (name, m) in engine.global_sub_modules.as_deref().into_iter().flatten() {
         global.modules.insert(name, m.as_ref().into());
     }
 
@@ -185,7 +187,16 @@ pub fn gen_metadata_to_json(
         .global_modules
         .iter()
         .filter(|m| !m.flags.contains(exclude_flags))
-        .flat_map(|m| m.iter_fn())
+        .flat_map(|m| {
+            #[cfg(feature = "metadata")]
+            if !m.doc().is_empty() {
+                if !global_doc.is_empty() {
+                    global_doc.push('\n');
+                }
+                global_doc.push_str(m.doc());
+            }
+            m.iter_fn()
+        })
         .for_each(|f| {
             #[allow(unused_mut)]
             let mut meta: FnMetadata = f.into();
@@ -213,7 +224,17 @@ pub fn gen_metadata_to_json(
 
     #[cfg(feature = "metadata")]
     if let Some(ast) = _ast {
-        global.doc = ast.doc();
+        if !ast.doc().is_empty() {
+            if !global_doc.is_empty() {
+                global_doc.push('\n');
+            }
+            global_doc.push_str(ast.doc());
+        }
+    }
+
+    #[cfg(feature = "metadata")]
+    {
+        global.doc = &global_doc;
     }
 
     serde_json::to_string_pretty(&global)

src/tokenizer.rs

@@ -5,7 +5,7 @@ use crate::engine::{
     KEYWORD_FN_PTR_CURRY, KEYWORD_IS_DEF_VAR, KEYWORD_PRINT, KEYWORD_THIS, KEYWORD_TYPE_OF,
 };
 use crate::func::native::OnParseTokenCallback;
-use crate::{Engine, Identifier, LexError, SmartString, StaticVec, INT, UNSIGNED_INT};
+use crate::{Engine, Identifier, LexError, Position, SmartString, StaticVec, INT, UNSIGNED_INT};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 use std::{
@@ -13,7 +13,6 @@ use std::{
     char, fmt,
     iter::{FusedIterator, Peekable},
     num::NonZeroUsize,
-    ops::{Add, AddAssign},
     rc::Rc,
     str::{Chars, FromStr},
 };
@@ -24,9 +23,9 @@ pub struct TokenizerControlBlock {
     /// Is the current tokenizer position within an interpolated text string?
     /// This flag allows switching the tokenizer back to _text_ parsing after an interpolation stream.
     pub is_within_text: bool,
-    /// Collection of global comments.
+    /// Global comments.
     #[cfg(feature = "metadata")]
-    pub global_comments: Vec<SmartString>,
+    pub global_comments: String,
 }
 
 impl TokenizerControlBlock {
@@ -37,7 +36,7 @@ impl TokenizerControlBlock {
         Self {
             is_within_text: false,
             #[cfg(feature = "metadata")]
-            global_comments: Vec::new(),
+            global_comments: String::new(),
         }
     }
 }
@@ -50,326 +49,12 @@ type LERR = LexError;
 /// Separator character for numbers.
 const NUMBER_SEPARATOR: char = '_';
 
+/// No token.
+pub const NO_TOKEN: Token = Token::NONE;
+
 /// A stream of tokens.
 pub type TokenStream<'a> = Peekable<TokenIterator<'a>>;
 
-/// A location (line number + character position) in the input script.
-///
-/// # Limitations
-///
-/// In order to keep footprint small, both line number and character position have 16-bit resolution,
-/// meaning they go up to a maximum of 65,535 lines and 65,535 characters per line.
-///
-/// Advancing beyond the maximum line length or maximum number of lines is not an error but has no effect.
-#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
-pub struct Position {
-    /// Line number: 0 = none
-    #[cfg(not(feature = "no_position"))]
-    line: u16,
-    /// Character position: 0 = BOL
-    #[cfg(not(feature = "no_position"))]
-    pos: u16,
-}
-
-impl Position {
-    /// A [`Position`] representing no position.
-    pub const NONE: Self = Self {
-        #[cfg(not(feature = "no_position"))]
-        line: 0,
-        #[cfg(not(feature = "no_position"))]
-        pos: 0,
-    };
-    /// A [`Position`] representing the first position.
-    pub const START: Self = Self {
-        #[cfg(not(feature = "no_position"))]
-        line: 1,
-        #[cfg(not(feature = "no_position"))]
-        pos: 0,
-    };
-
-    /// Create a new [`Position`].
-    ///
-    /// `line` must not be zero.
-    ///
-    /// If `position` is zero, then it is at the beginning of a line.
-    ///
-    /// # Panics
-    ///
-    /// Panics if `line` is zero.
-    #[inline]
-    #[must_use]
-    pub const fn new(line: u16, position: u16) -> Self {
-        assert!(line != 0, "line cannot be zero");
-
-        let _pos = position;
-
-        Self {
-            #[cfg(not(feature = "no_position"))]
-            line,
-            #[cfg(not(feature = "no_position"))]
-            pos: _pos,
-        }
-    }
-    /// Get the line number (1-based), or [`None`] if there is no position.
-    #[inline]
-    #[must_use]
-    pub const fn line(self) -> Option<usize> {
-        #[cfg(not(feature = "no_position"))]
-        return if self.is_none() {
-            None
-        } else {
-            Some(self.line as usize)
-        };
-
-        #[cfg(feature = "no_position")]
-        return None;
-    }
-    /// Get the character position (1-based), or [`None`] if at beginning of a line.
-    #[inline]
-    #[must_use]
-    pub const fn position(self) -> Option<usize> {
-        #[cfg(not(feature = "no_position"))]
-        return if self.is_none() || self.pos == 0 {
-            None
-        } else {
-            Some(self.pos as usize)
-        };
-
-        #[cfg(feature = "no_position")]
-        return None;
-    }
-    /// Advance by one character position.
-    #[inline]
-    pub(crate) fn advance(&mut self) {
-        #[cfg(not(feature = "no_position"))]
-        {
-            assert!(!self.is_none(), "cannot advance Position::none");
-
-            // Advance up to maximum position
-            if self.pos < u16::MAX {
-                self.pos += 1;
-            }
-        }
-    }
-    /// Go backwards by one character position.
-    ///
-    /// # Panics
-    ///
-    /// Panics if already at beginning of a line - cannot rewind to a previous line.
-    #[inline]
-    pub(crate) fn rewind(&mut self) {
-        #[cfg(not(feature = "no_position"))]
-        {
-            assert!(!self.is_none(), "cannot rewind Position::none");
-            assert!(self.pos > 0, "cannot rewind at position 0");
-            self.pos -= 1;
-        }
-    }
-    /// Advance to the next line.
-    #[inline]
-    pub(crate) fn new_line(&mut self) {
-        #[cfg(not(feature = "no_position"))]
-        {
-            assert!(!self.is_none(), "cannot advance Position::none");
-
-            // Advance up to maximum position
-            if self.line < u16::MAX {
-                self.line += 1;
-                self.pos = 0;
-            }
-        }
-    }
-    /// Is this [`Position`] at the beginning of a line?
-    #[inline]
-    #[must_use]
-    pub const fn is_beginning_of_line(self) -> bool {
-        #[cfg(not(feature = "no_position"))]
-        return self.pos == 0 && !self.is_none();
-        #[cfg(feature = "no_position")]
-        return false;
-    }
-    /// Is there no [`Position`]?
-    #[inline]
-    #[must_use]
-    pub const fn is_none(self) -> bool {
-        #[cfg(not(feature = "no_position"))]
-        return self.line == 0 && self.pos == 0;
-        #[cfg(feature = "no_position")]
-        return true;
-    }
-    /// Returns an fallback [`Position`] if it is [`NONE`][Position::NONE]?
-    #[inline]
-    #[must_use]
-    pub const fn or_else(self, pos: Self) -> Self {
-        if self.is_none() {
-            pos
-        } else {
-            self
-        }
-    }
-    /// Print this [`Position`] for debug purposes.
-    #[inline]
-    pub(crate) fn debug_print(self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if !self.is_none() {
-            write!(_f, " @ {:?}", self)?;
-        }
-        Ok(())
-    }
-}
-
-impl Default for Position {
-    #[inline(always)]
-    #[must_use]
-    fn default() -> Self {
-        Self::START
-    }
-}
-
-impl fmt::Display for Position {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if self.is_none() {
-            write!(f, "none")?;
-        } else {
-            #[cfg(not(feature = "no_position"))]
-            write!(f, "line {}, position {}", self.line, self.pos)?;
-            #[cfg(feature = "no_position")]
-            unreachable!("no position");
-        }
-
-        Ok(())
-    }
-}
-
-impl fmt::Debug for Position {
-    #[cold]
-    #[inline(never)]
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if self.is_none() {
-            f.write_str("none")
-        } else {
-            #[cfg(not(feature = "no_position"))]
-            if self.is_beginning_of_line() {
-                write!(f, "{}", self.line)
-            } else {
-                write!(f, "{}:{}", self.line, self.pos)
-            }
-
-            #[cfg(feature = "no_position")]
-            unreachable!("no position");
-        }
-    }
-}
-
-impl Add for Position {
-    type Output = Self;
-
-    fn add(self, rhs: Self) -> Self::Output {
-        if rhs.is_none() {
-            self
-        } else {
-            #[cfg(not(feature = "no_position"))]
-            return Self {
-                line: self.line + rhs.line - 1,
-                pos: if rhs.is_beginning_of_line() {
-                    self.pos
-                } else {
-                    self.pos + rhs.pos - 1
-                },
-            };
-            #[cfg(feature = "no_position")]
-            unreachable!("no position");
-        }
-    }
-}
-
-impl AddAssign for Position {
-    fn add_assign(&mut self, rhs: Self) {
-        *self = *self + rhs;
-    }
-}
-
-/// _(internals)_ A span consisting of a starting and an ending [positions][Position].
-/// Exported under the `internals` feature only.
-#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
-pub struct Span {
-    /// Starting [position][Position].
-    start: Position,
-    /// Ending [position][Position].
-    end: Position,
-}
-
-impl Default for Span {
-    #[inline(always)]
-    #[must_use]
-    fn default() -> Self {
-        Self::NONE
-    }
-}
-
-impl Span {
-    /// Empty [`Span`].
-    pub const NONE: Self = Self::new(Position::NONE, Position::NONE);
-
-    /// Create a new [`Span`].
-    #[inline(always)]
-    #[must_use]
-    pub const fn new(start: Position, end: Position) -> Self {
-        Self { start, end }
-    }
-    /// Is this [`Span`] non-existent?
-    #[inline]
-    #[must_use]
-    pub const fn is_none(&self) -> bool {
-        self.start.is_none() && self.end.is_none()
-    }
-    /// Get the [`Span`]'s starting [position][Position].
-    #[inline(always)]
-    #[must_use]
-    pub const fn start(&self) -> Position {
-        self.start
-    }
-    /// Get the [`Span`]'s ending [position][Position].
-    #[inline(always)]
-    #[must_use]
-    pub const fn end(&self) -> Position {
-        self.end
-    }
-}
-
-impl fmt::Display for Span {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let _f = f;
-
-        #[cfg(not(feature = "no_position"))]
-        match (self.start(), self.end()) {
-            (Position::NONE, Position::NONE) => write!(_f, "{:?}", Position::NONE),
-            (Position::NONE, end) => write!(_f, "..{:?}", end),
-            (start, Position::NONE) => write!(_f, "{:?}", start),
-            (start, end) if start.line() != end.line() => {
-                write!(_f, "{:?}-{:?}", start, end)
-            }
-            (start, end) => write!(
-                _f,
-                "{}:{}-{}",
-                start.line().unwrap(),
-                start.position().unwrap_or(0),
-                end.position().unwrap_or(0)
-            ),
-        }
-
-        #[cfg(feature = "no_position")]
-        Ok(())
-    }
-}
-
-impl fmt::Debug for Span {
-    #[cold]
-    #[inline(never)]
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(self, f)
-    }
-}
-
 /// _(internals)_ A Rhai language token.
 /// Exported under the `internals` feature only.
 #[derive(Debug, PartialEq, Clone, Hash)]
@@ -489,6 +174,8 @@ pub enum Token {
     For,
     /// `in`
     In,
+    /// `!in`
+    NotIn,
     /// `<`
     LessThan,
     /// `>`
@@ -575,7 +262,7 @@ pub enum Token {
     /// A lexer error.
     LexError(Box<LexError>),
     /// A comment block.
-    Comment(Box<SmartString>),
+    Comment(Box<String>),
     /// A reserved symbol.
     Reserved(Box<SmartString>),
     /// A custom keyword.
@@ -584,7 +271,10 @@ pub enum Token {
     #[cfg(not(feature = "no_custom_syntax"))]
     Custom(Box<SmartString>),
     /// End of the input stream.
+    /// Used as a placeholder for the end of input.
     EOF,
+    /// Placeholder to indicate the lack of a token.
+    NONE,
 }
 
 impl fmt::Display for Token {
@@ -610,6 +300,7 @@ impl fmt::Display for Token {
             Comment(s) => f.write_str(s),
 
             EOF => f.write_str("{EOF}"),
+            NONE => f.write_str("{NONE}"),
 
             token => f.write_str(token.literal_syntax()),
         }
@@ -638,7 +329,7 @@ impl Token {
             Custom(..) => false,
             LexError(..) | Comment(..) => false,
 
-            EOF => false,
+            EOF | NONE => false,
 
             _ => true,
         }
@@ -696,6 +387,7 @@ impl Token {
             Loop => "loop",
             For => "for",
             In => "in",
+            NotIn => "!in",
             LessThan => "<",
             GreaterThan => ">",
             Bang => "!",
@@ -750,37 +442,43 @@ impl Token {
     #[inline]
     #[must_use]
     pub const fn is_op_assignment(&self) -> bool {
+        #[allow(clippy::enum_glob_use)]
+        use Token::*;
+
         matches!(
             self,
-            Self::PlusAssign
-                | Self::MinusAssign
-                | Self::MultiplyAssign
-                | Self::DivideAssign
-                | Self::LeftShiftAssign
-                | Self::RightShiftAssign
-                | Self::ModuloAssign
-                | Self::PowerOfAssign
-                | Self::AndAssign
-                | Self::OrAssign
-                | Self::XOrAssign
+            PlusAssign
+                | MinusAssign
+                | MultiplyAssign
+                | DivideAssign
+                | LeftShiftAssign
+                | RightShiftAssign
+                | ModuloAssign
+                | PowerOfAssign
+                | AndAssign
+                | OrAssign
+                | XOrAssign
         )
     }
 
     /// Get the corresponding operator of the token if it is an op-assignment operator.
     #[must_use]
     pub const fn get_base_op_from_assignment(&self) -> Option<Self> {
+        #[allow(clippy::enum_glob_use)]
+        use Token::*;
+
         Some(match self {
-            Self::PlusAssign => Self::Plus,
-            Self::MinusAssign => Self::Minus,
-            Self::MultiplyAssign => Self::Multiply,
-            Self::DivideAssign => Self::Divide,
-            Self::LeftShiftAssign => Self::LeftShift,
-            Self::RightShiftAssign => Self::RightShift,
-            Self::ModuloAssign => Self::Modulo,
-            Self::PowerOfAssign => Self::PowerOf,
-            Self::AndAssign => Self::Ampersand,
-            Self::OrAssign => Self::Pipe,
-            Self::XOrAssign => Self::XOr,
+            PlusAssign => Plus,
+            MinusAssign => Minus,
+            MultiplyAssign => Multiply,
+            DivideAssign => Divide,
+            LeftShiftAssign => LeftShift,
+            RightShiftAssign => RightShift,
+            ModuloAssign => Modulo,
+            PowerOfAssign => PowerOf,
+            AndAssign => Ampersand,
+            OrAssign => Pipe,
+            XOrAssign => XOr,
             _ => return None,
         })
     }
@@ -789,37 +487,42 @@ impl Token {
     #[inline]
     #[must_use]
     pub const fn has_op_assignment(&self) -> bool {
+        #[allow(clippy::enum_glob_use)]
+        use Token::*;
+
         matches!(
             self,
-            Self::Plus
-                | Self::Minus
-                | Self::Multiply
-                | Self::Divide
-                | Self::LeftShift
-                | Self::RightShift
-                | Self::Modulo
-                | Self::PowerOf
-                | Self::Ampersand
-                | Self::Pipe
-                | Self::XOr
+            Plus | Minus
+                | Multiply
+                | Divide
+                | LeftShift
+                | RightShift
+                | Modulo
+                | PowerOf
+                | Ampersand
+                | Pipe
+                | XOr
         )
     }
 
     /// Get the corresponding op-assignment operator of the token.
     #[must_use]
     pub const fn convert_to_op_assignment(&self) -> Option<Self> {
+        #[allow(clippy::enum_glob_use)]
+        use Token::*;
+
         Some(match self {
-            Self::Plus => Self::PlusAssign,
-            Self::Minus => Self::MinusAssign,
-            Self::Multiply => Self::MultiplyAssign,
-            Self::Divide => Self::DivideAssign,
-            Self::LeftShift => Self::LeftShiftAssign,
-            Self::RightShift => Self::RightShiftAssign,
-            Self::Modulo => Self::ModuloAssign,
-            Self::PowerOf => Self::PowerOfAssign,
-            Self::Ampersand => Self::AndAssign,
-            Self::Pipe => Self::OrAssign,
-            Self::XOr => Self::XOrAssign,
+            Plus => PlusAssign,
+            Minus => MinusAssign,
+            Multiply => MultiplyAssign,
+            Divide => DivideAssign,
+            LeftShift => LeftShiftAssign,
+            RightShift => RightShiftAssign,
+            Modulo => ModuloAssign,
+            PowerOf => PowerOfAssign,
+            Ampersand => AndAssign,
+            Pipe => OrAssign,
+            XOr => XOrAssign,
             _ => return None,
         })
     }
@@ -871,6 +574,7 @@ impl Token {
             "loop" => Loop,
             "for" => For,
             "in" => In,
+            "!in" => NotIn,
             "<" => LessThan,
             ">" => GreaterThan,
             "!" => Bang,
@@ -956,13 +660,6 @@ impl Token {
         }
     }
 
-    /// Is this token [`EOF`][Token::EOF]?
-    #[inline(always)]
-    #[must_use]
-    pub const fn is_eof(&self) -> bool {
-        matches!(self, Self::EOF)
-    }
-
     /// If another operator is after these, it's probably a unary operator
     /// (not sure about `fn` name).
     #[must_use]
@@ -1018,6 +715,7 @@ impl Token {
             While            |
             Until            |
             In               |
+            NotIn            |
             And              |
             AndAssign        |
             Or               |
@@ -1049,7 +747,7 @@ impl Token {
 
             EqualsTo | NotEqualsTo => 90,
 
-            In => 110,
+            In | NotIn => 110,
 
             LessThan | LessThanEqualsTo | GreaterThan | GreaterThanEqualsTo => 130,
 
@@ -1170,7 +868,7 @@ impl From<Token> for String {
 #[derive(Debug, Clone, Eq, PartialEq, Default)]
 pub struct TokenizeState {
     /// Maximum length of a string.
-    pub max_string_size: Option<NonZeroUsize>,
+    pub max_string_len: Option<NonZeroUsize>,
     /// Can the next token be a unary operator?
     pub next_token_cannot_be_unary: bool,
     /// Shared object to allow controlling the tokenizer externally.
@@ -1197,6 +895,18 @@ pub trait InputStream {
     fn peek_next(&mut self) -> Option<char>;
 }
 
+/// Return error if the string is longer than the maximum length.
+#[inline]
+fn ensure_string_len_within_limit(max: Option<NonZeroUsize>, value: &str) -> Result<(), LexError> {
+    if let Some(max) = max {
+        if value.len() > max.get() {
+            return Err(LexError::StringTooLong(max.get()));
+        }
+    }
+
+    Ok(())
+}
+
 /// _(internals)_ Parse a string literal ended by a specified termination character.
 /// Exported under the `internals` feature only.
 ///
@@ -1286,11 +996,8 @@ pub fn parse_string_literal(
             break;
         }
 
-        if let Some(max) = state.max_string_size {
-            if result.len() > max.get() {
-                return Err((LexError::StringTooLong(max.get()), *pos));
-            }
-        }
+        ensure_string_len_within_limit(state.max_string_len, &result)
+            .map_err(|err| (err, start))?;
 
         // Close wrapper
         if termination_char == next_char && escape.is_empty() {
@@ -1425,11 +1132,7 @@ pub fn parse_string_literal(
         }
     }
 
-    if let Some(max) = state.max_string_size {
-        if result.len() > max.get() {
-            return Err((LexError::StringTooLong(max.get()), *pos));
-        }
-    }
+    ensure_string_len_within_limit(state.max_string_len, &result).map_err(|err| (err, start))?;
 
     Ok((result, interpolated, first_char))
 }
@@ -1446,7 +1149,7 @@ fn scan_block_comment(
     stream: &mut impl InputStream,
     level: usize,
     pos: &mut Position,
-    comment: Option<&mut SmartString>,
+    comment: Option<&mut String>,
 ) -> usize {
     let mut level = level;
     let mut comment = comment;
@@ -1541,7 +1244,7 @@ fn get_next_token_inner(
     if state.comment_level > 0 {
         let start_pos = *pos;
         let mut comment = if state.include_comments {
-            Some(SmartString::new_const())
+            Some(String::new())
         } else {
             None
         };
@@ -1748,11 +1451,17 @@ fn get_next_token_inner(
             // letter or underscore ...
             #[cfg(not(feature = "unicode-xid-ident"))]
             ('a'..='z' | '_' | 'A'..='Z', ..) => {
-                return Some(get_token_as_identifier(stream, pos, start_pos, c));
+                return Some(
+                    parse_identifier_token(stream, pos, start_pos, c)
+                        .unwrap_or_else(|err| (Token::LexError(err.into()), start_pos)),
+                );
             }
             #[cfg(feature = "unicode-xid-ident")]
             (ch, ..) if unicode_xid::UnicodeXID::is_xid_start(ch) || ch == '_' => {
-                return Some(get_token_as_identifier(stream, pos, start_pos, c));
+                return Some(
+                    parse_identifier_token(stream, pos, start_pos, c)
+                        .unwrap_or_else(|err| (Token::LexError(err.into()), start_pos)),
+                );
             }
 
             // " - string literal
@@ -1928,7 +1637,7 @@ fn get_next_token_inner(
             ('/', '/') => {
                 eat_next(stream, pos);
 
-                let mut comment: Option<SmartString> = match stream.peek_next() {
+                let mut comment: Option<String> = match stream.peek_next() {
                     #[cfg(not(feature = "no_function"))]
                     #[cfg(feature = "metadata")]
                     Some('/') => {
@@ -1971,11 +1680,13 @@ fn get_next_token_inner(
                 if let Some(comment) = comment {
                     match comment {
                         #[cfg(feature = "metadata")]
-                        _ if comment.starts_with("//!") => state
-                            .tokenizer_control
-                            .borrow_mut()
-                            .global_comments
-                            .push(comment),
+                        _ if comment.starts_with("//!") => {
+                            let g = &mut state.tokenizer_control.borrow_mut().global_comments;
+                            if !g.is_empty() {
+                                g.push('\n');
+                            }
+                            g.push_str(&comment);
+                        }
                         _ => return Some((Token::Comment(comment.into()), start_pos)),
                     }
                 }
@@ -1984,7 +1695,7 @@ fn get_next_token_inner(
                 state.comment_level = 1;
                 eat_next(stream, pos);
 
-                let mut comment: Option<SmartString> = match stream.peek_next() {
+                let mut comment: Option<String> = match stream.peek_next() {
                     #[cfg(not(feature = "no_function"))]
                     #[cfg(feature = "metadata")]
                     Some('*') => {
@@ -2119,6 +1830,15 @@ fn get_next_token_inner(
             }
             ('>', ..) => return Some((Token::GreaterThan, start_pos)),
 
+            ('!', 'i') => {
+                eat_next(stream, pos);
+                if stream.peek_next() == Some('n') {
+                    eat_next(stream, pos);
+                    return Some((Token::NotIn, start_pos));
+                }
+                stream.unget('i');
+                return Some((Token::Bang, start_pos));
+            }
             ('!', '=') => {
                 eat_next(stream, pos);
 
@@ -2220,12 +1940,12 @@ fn get_next_token_inner(
 }
 
 /// Get the next token, parsing it as an identifier.
-fn get_token_as_identifier(
+fn parse_identifier_token(
     stream: &mut impl InputStream,
     pos: &mut Position,
     start_pos: Position,
     first_char: char,
-) -> (Token, Position) {
+) -> Result<(Token, Position), LexError> {
     let mut identifier = SmartString::new_const();
     identifier.push(first_char);
 
@@ -2240,19 +1960,20 @@ fn get_token_as_identifier(
     }
 
     if let Some(token) = Token::lookup_symbol_from_syntax(&identifier) {
-        return (token, start_pos);
-    } else if Token::is_reserved_keyword(&identifier) {
-        return (Token::Reserved(Box::new(identifier)), start_pos);
+        return Ok((token, start_pos));
+    }
+    if Token::is_reserved_keyword(&identifier) {
+        return Ok((Token::Reserved(Box::new(identifier)), start_pos));
     }
 
     if !is_valid_identifier(&identifier) {
-        return (
+        return Ok((
             Token::LexError(LERR::MalformedIdentifier(identifier.to_string()).into()),
             start_pos,
-        );
+        ));
     }
 
-    (Token::Identifier(identifier.into()), start_pos)
+    Ok((Token::Identifier(identifier.into()), start_pos))
 }
 
 /// Is a keyword allowed as a function?
@@ -2435,7 +2156,7 @@ impl<'a> Iterator for TokenIterator<'a> {
             Some((Token::Reserved(s), pos)) => (match
                 (s.as_str(),
                     #[cfg(not(feature = "no_custom_syntax"))]
-                    self.engine.custom_keywords.as_ref().map_or(false, |m| m.contains_key(&*s)),
+                    self.engine.custom_keywords.as_deref().map_or(false, |m| m.contains_key(&*s)),
                     #[cfg(feature = "no_custom_syntax")]
                     false
                 )
@@ -2472,7 +2193,7 @@ impl<'a> Iterator for TokenIterator<'a> {
                 #[cfg(feature = "no_custom_syntax")]
                 (.., true) => unreachable!("no custom operators"),
                 // Reserved keyword that is not custom and disabled.
-                (token, false) if self.engine.disabled_symbols.as_ref().map_or(false,|m| m.contains(token)) => {
+                (token, false) if self.engine.disabled_symbols.as_deref().map_or(false,|m| m.contains(token)) => {
                     let msg = format!("reserved {} '{token}' is disabled", if is_valid_identifier(token) { "keyword"} else {"symbol"});
                     Token::LexError(LERR::ImproperSymbol(s.to_string(), msg).into())
                 },
@@ -2481,13 +2202,13 @@ impl<'a> Iterator for TokenIterator<'a> {
             }, pos),
             // Custom keyword
             #[cfg(not(feature = "no_custom_syntax"))]
-            Some((Token::Identifier(s), pos)) if self.engine.custom_keywords.as_ref().map_or(false,|m| m.contains_key(&*s)) => {
+            Some((Token::Identifier(s), pos)) if self.engine.custom_keywords.as_deref().map_or(false,|m| m.contains_key(&*s)) => {
                 (Token::Custom(s), pos)
             }
             // Custom keyword/symbol - must be disabled
             #[cfg(not(feature = "no_custom_syntax"))]
-            Some((token, pos)) if token.is_literal() && self.engine.custom_keywords.as_ref().map_or(false,|m| m.contains_key(token.literal_syntax())) => {
-                if self.engine.disabled_symbols.as_ref().map_or(false,|m| m.contains(token.literal_syntax())) {
+            Some((token, pos)) if token.is_literal() && self.engine.custom_keywords.as_deref().map_or(false,|m| m.contains_key(token.literal_syntax())) => {
+                if self.engine.disabled_symbols.as_deref().map_or(false,|m| m.contains(token.literal_syntax())) {
                     // Disabled standard keyword/symbol
                     (Token::Custom(Box::new(token.literal_syntax().into())), pos)
                 } else {
@@ -2496,7 +2217,7 @@ impl<'a> Iterator for TokenIterator<'a> {
                 }
             }
             // Disabled symbol
-            Some((token, pos)) if token.is_literal() && self.engine.disabled_symbols.as_ref().map_or(false,|m| m.contains(token.literal_syntax())) => {
+            Some((token, pos)) if token.is_literal() && self.engine.disabled_symbols.as_deref().map_or(false,|m| m.contains(token.literal_syntax())) => {
                 (Token::Reserved(Box::new(token.literal_syntax().into())), pos)
             }
             // Normal symbol
@@ -2554,10 +2275,7 @@ impl Engine {
             TokenIterator {
                 engine: self,
                 state: TokenizeState {
-                    #[cfg(not(feature = "unchecked"))]
-                    max_string_size: self.limits.max_string_size,
-                    #[cfg(feature = "unchecked")]
-                    max_string_size: None,
+                    max_string_len: NonZeroUsize::new(self.max_string_size()),
                     next_token_cannot_be_unary: false,
                     tokenizer_control: buffer,
                     comment_level: 0,

src/types/custom_types.rs

@@ -1,7 +1,7 @@
 //! Collection of custom types.
 
 use crate::Identifier;
-use std::{any::type_name, collections::BTreeMap, fmt};
+use std::{any::type_name, collections::BTreeMap};
 
 /// _(internals)_ Information for a custom type.
 /// Exported under the `internals` feature only.
@@ -13,18 +13,9 @@ pub struct CustomTypeInfo {
 
 /// _(internals)_ A collection of custom types.
 /// Exported under the `internals` feature only.
-#[derive(Clone, Hash)]
+#[derive(Debug, Clone, Hash)]
 pub struct CustomTypesCollection(BTreeMap<Identifier, CustomTypeInfo>);
 
-impl fmt::Debug for CustomTypesCollection {
-    #[cold]
-    #[inline(never)]
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("CustomTypesCollection ")?;
-        f.debug_map().entries(self.0.iter()).finish()
-    }
-}
-
 impl Default for CustomTypesCollection {
     #[inline(always)]
     fn default() -> Self {
@@ -65,6 +56,7 @@ impl CustomTypesCollection {
     }
     /// Find a custom type.
     #[inline(always)]
+    #[must_use]
     pub fn get(&self, key: &str) -> Option<&CustomTypeInfo> {
         self.0.get(key)
     }

src/types/dynamic.rs

@@ -1,6 +1,6 @@
 //! Helper module which defines the [`Dynamic`] data type.
 
-use crate::{reify, ExclusiveRange, FnPtr, ImmutableString, InclusiveRange, INT};
+use crate::{ExclusiveRange, FnPtr, ImmutableString, InclusiveRange, INT};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 use std::{
@@ -49,11 +49,13 @@ pub type Tag = i16;
 const DEFAULT_TAG_VALUE: Tag = 0;
 
 /// Dynamic type containing any value.
+#[must_use]
 pub struct Dynamic(pub(crate) Union);
 
 /// Internal [`Dynamic`] representation.
 ///
 /// Most variants are boxed to reduce the size.
+#[must_use]
 pub enum Union {
     /// An error value which should not exist.
     Null,
@@ -107,10 +109,12 @@ pub enum Union {
 /// This type provides transparent interoperability between normal [`Dynamic`] and shared
 /// [`Dynamic`] values.
 #[derive(Debug)]
+#[must_use]
 pub struct DynamicReadLock<'d, T: Clone>(DynamicReadLockInner<'d, T>);
 
 /// Different types of read guards for [`DynamicReadLock`].
 #[derive(Debug)]
+#[must_use]
 enum DynamicReadLockInner<'d, T: Clone> {
     /// A simple reference to a non-shared value.
     Reference(&'d T),
@@ -139,10 +143,12 @@ impl<'d, T: Any + Clone> Deref for DynamicReadLock<'d, T> {
 /// This type provides transparent interoperability between normal [`Dynamic`] and shared
 /// [`Dynamic`] values.
 #[derive(Debug)]
+#[must_use]
 pub struct DynamicWriteLock<'d, T: Clone>(DynamicWriteLockInner<'d, T>);
 
 /// Different types of write guards for [`DynamicReadLock`].
 #[derive(Debug)]
+#[must_use]
 enum DynamicWriteLockInner<'d, T: Clone> {
     /// A simple mutable reference to a non-shared value.
     Reference(&'d mut T),
@@ -686,7 +692,6 @@ impl Clone for Dynamic {
 
 impl Default for Dynamic {
     #[inline(always)]
-    #[must_use]
     fn default() -> Self {
         Self::UNIT
     }
@@ -852,19 +857,16 @@ impl Dynamic {
 
     /// Create a new [`Dynamic`] from a [`bool`].
     #[inline(always)]
-    #[must_use]
     pub const fn from_bool(value: bool) -> Self {
         Self(Union::Bool(value, DEFAULT_TAG_VALUE, ReadWrite))
     }
     /// Create a new [`Dynamic`] from an [`INT`].
     #[inline(always)]
-    #[must_use]
     pub const fn from_int(value: INT) -> Self {
         Self(Union::Int(value, DEFAULT_TAG_VALUE, ReadWrite))
     }
     /// Create a new [`Dynamic`] from a [`char`].
     #[inline(always)]
-    #[must_use]
     pub const fn from_char(value: char) -> Self {
         Self(Union::Char(value, DEFAULT_TAG_VALUE, ReadWrite))
     }
@@ -873,7 +875,6 @@ impl Dynamic {
     /// Not available under `no_float`.
     #[cfg(not(feature = "no_float"))]
     #[inline(always)]
-    #[must_use]
     pub const fn from_float(value: crate::FLOAT) -> Self {
         Self(Union::Float(
             super::FloatWrapper::new(value),
@@ -886,28 +887,24 @@ impl Dynamic {
     /// Exported under the `decimal` feature only.
     #[cfg(feature = "decimal")]
     #[inline(always)]
-    #[must_use]
     pub fn from_decimal(value: rust_decimal::Decimal) -> Self {
         Self(Union::Decimal(value.into(), DEFAULT_TAG_VALUE, ReadWrite))
     }
     /// Create a [`Dynamic`] from an [`Array`][crate::Array].
     #[cfg(not(feature = "no_index"))]
     #[inline(always)]
-    #[must_use]
     pub fn from_array(array: crate::Array) -> Self {
         Self(Union::Array(array.into(), DEFAULT_TAG_VALUE, ReadWrite))
     }
     /// Create a [`Dynamic`] from a [`Blob`][crate::Blob].
     #[cfg(not(feature = "no_index"))]
     #[inline(always)]
-    #[must_use]
     pub fn from_blob(blob: crate::Blob) -> Self {
         Self(Union::Blob(blob.into(), DEFAULT_TAG_VALUE, ReadWrite))
     }
     /// Create a [`Dynamic`] from a [`Map`][crate::Map].
     #[cfg(not(feature = "no_object"))]
     #[inline(always)]
-    #[must_use]
     pub fn from_map(map: crate::Map) -> Self {
         Self(Union::Map(map.into(), DEFAULT_TAG_VALUE, ReadWrite))
     }
@@ -916,7 +913,6 @@ impl Dynamic {
     /// Not available under `no-std` or `no_time`.
     #[cfg(not(feature = "no_time"))]
     #[inline(always)]
-    #[must_use]
     pub fn from_timestamp(value: Instant) -> Self {
         Self(Union::TimeStamp(value.into(), DEFAULT_TAG_VALUE, ReadWrite))
     }
@@ -991,7 +987,6 @@ impl Dynamic {
     }
     /// Make this [`Dynamic`] read-only (i.e. a constant).
     #[inline(always)]
-    #[must_use]
     pub fn into_read_only(self) -> Self {
         let mut value = self;
         value.set_access_mode(AccessMode::ReadOnly);
@@ -1085,7 +1080,6 @@ impl Dynamic {
     /// assert_eq!(new_result.to_string(), "hello");
     /// ```
     #[inline]
-    #[must_use]
     pub fn from<T: Variant + Clone>(value: T) -> Self {
         // Coded this way in order to maximally leverage potentials for dead-code removal.
 
@@ -1143,7 +1137,6 @@ impl Dynamic {
     /// If the [`Dynamic`] value is already shared, this method returns itself.
     #[cfg(not(feature = "no_closure"))]
     #[inline]
-    #[must_use]
     pub fn into_shared(self) -> Self {
         let _access = self.access_mode();
 
@@ -1182,6 +1175,7 @@ impl Dynamic {
     /// ```
     #[inline]
     #[must_use]
+    #[allow(unused_mut)]
     pub fn try_cast<T: Any>(mut self) -> Option<T> {
         // Coded this way in order to maximally leverage potentials for dead-code removal.
 
@@ -1365,7 +1359,6 @@ impl Dynamic {
     ///
     /// If the [`Dynamic`] is a shared value, it returns a cloned copy of the shared value.
     #[inline]
-    #[must_use]
     pub fn flatten_clone(&self) -> Self {
         match self.0 {
             #[cfg(not(feature = "no_closure"))]
@@ -1380,7 +1373,6 @@ impl Dynamic {
     /// If the [`Dynamic`] is a shared value, it returns the shared value if there are no
     /// outstanding references, or a cloned copy.
     #[inline]
-    #[must_use]
     pub fn flatten(self) -> Self {
         match self.0 {
             #[cfg(not(feature = "no_closure"))]
@@ -1451,7 +1443,6 @@ impl Dynamic {
     /// Under the `sync` feature, this call may deadlock, or [panic](https://doc.rust-lang.org/std/sync/struct.RwLock.html#panics-1).
     /// Otherwise, this call panics if the data is currently borrowed for write.
     #[inline]
-    #[must_use]
     pub fn read_lock<T: Any + Clone>(&self) -> Option<DynamicReadLock<T>> {
         match self.0 {
             #[cfg(not(feature = "no_closure"))]
@@ -1483,7 +1474,6 @@ impl Dynamic {
     /// Under the `sync` feature, this call may deadlock, or [panic](https://doc.rust-lang.org/std/sync/struct.RwLock.html#panics-1).
     /// Otherwise, this call panics if the data is currently borrowed for write.
     #[inline]
-    #[must_use]
     pub fn write_lock<T: Any + Clone>(&mut self) -> Option<DynamicWriteLock<T>> {
         match self.0 {
             #[cfg(not(feature = "no_closure"))]

src/types/error.rs

@@ -135,22 +135,20 @@ impl fmt::Display for EvalAltResult {
 
             #[cfg(not(feature = "no_function"))]
             Self::ErrorInFunctionCall(s, src, err, ..) if crate::parser::is_anonymous_fn(s) => {
-                write!(f, "{err} in call to closure")?;
+                write!(f, "{err}\nin closure call")?;
                 if !src.is_empty() {
                     write!(f, " @ '{src}'")?;
                 }
             }
             Self::ErrorInFunctionCall(s, src, err, ..) => {
-                write!(f, "{err} in call to function {s}")?;
+                write!(f, "{err}\nin call to function '{s}'")?;
                 if !src.is_empty() {
                     write!(f, " @ '{src}'")?;
                 }
             }
 
-            Self::ErrorInModule(s, err, ..) if s.is_empty() => {
-                write!(f, "Error in module > {err}")?
-            }
-            Self::ErrorInModule(s, err, ..) => write!(f, "Error in module '{s}' > {err}")?,
+            Self::ErrorInModule(s, err, ..) if s.is_empty() => write!(f, "{err}\nin module")?,
+            Self::ErrorInModule(s, err, ..) => write!(f, "{err}\nin module '{s}'")?,
 
             Self::ErrorVariableExists(s, ..) => write!(f, "Variable already defined: {s}")?,
             Self::ErrorForbiddenVariable(s, ..) => write!(f, "Forbidden variable name: {s}")?,
@@ -159,16 +157,14 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorIndexNotFound(s, ..) => write!(f, "Invalid index: {s}")?,
             Self::ErrorFunctionNotFound(s, ..) => write!(f, "Function not found: {s}")?,
             Self::ErrorModuleNotFound(s, ..) => write!(f, "Module not found: {s}")?,
-            Self::ErrorDataRace(s, ..) => {
-                write!(f, "Data race detected when accessing variable: {s}")?
-            }
+            Self::ErrorDataRace(s, ..) => write!(f, "Data race detected on variable '{s}'")?,
 
             Self::ErrorDotExpr(s, ..) if s.is_empty() => f.write_str("Malformed dot expression")?,
             Self::ErrorDotExpr(s, ..) => f.write_str(s)?,
 
             Self::ErrorIndexingType(s, ..) => write!(f, "Indexer unavailable: {s}")?,
             Self::ErrorUnboundThis(..) => f.write_str("'this' not bound")?,
-            Self::ErrorFor(..) => f.write_str("For loop expects an iterable type")?,
+            Self::ErrorFor(..) => f.write_str("For loop expects iterable type")?,
             Self::ErrorTooManyOperations(..) => f.write_str("Too many operations")?,
             Self::ErrorTooManyModules(..) => f.write_str("Too many modules imported")?,
             Self::ErrorStackOverflow(..) => f.write_str("Stack overflow")?,
@@ -188,31 +184,25 @@ impl fmt::Display for EvalAltResult {
                 if s.starts_with(crate::engine::FN_GET) =>
             {
                 let prop = &s[crate::engine::FN_GET.len()..];
-                write!(
-                    f,
-                    "Property {prop} is not pure and cannot be accessed on a constant"
-                )?
+                write!(f, "Non-pure property {prop} cannot be accessed on constant")?
             }
             #[cfg(not(feature = "no_object"))]
             Self::ErrorNonPureMethodCallOnConstant(s, ..)
                 if s.starts_with(crate::engine::FN_SET) =>
             {
                 let prop = &s[crate::engine::FN_SET.len()..];
-                write!(f, "Cannot modify property '{prop}' of a constant")?
+                write!(f, "Cannot modify property '{prop}' of constant")?
             }
             #[cfg(not(feature = "no_index"))]
             Self::ErrorNonPureMethodCallOnConstant(s, ..) if s == crate::engine::FN_IDX_GET => {
-                write!(
-                    f,
-                    "Indexer is not pure and cannot be accessed on a constant"
-                )?
+                write!(f, "Non-pure indexer cannot be accessed on constant")?
             }
             #[cfg(not(feature = "no_index"))]
             Self::ErrorNonPureMethodCallOnConstant(s, ..) if s == crate::engine::FN_IDX_SET => {
-                write!(f, "Cannot assign to the indexer of a constant")?
+                write!(f, "Cannot assign to indexer of constant")?
             }
             Self::ErrorNonPureMethodCallOnConstant(s, ..) => {
-                write!(f, "Non-pure method '{s}' cannot be called on a constant")?
+                write!(f, "Non-pure method '{s}' cannot be called on constant")?
             }
 
             Self::ErrorAssignmentToConstant(s, ..) => write!(f, "Cannot modify constant {s}")?,
@@ -230,8 +220,8 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorArithmetic(s, ..) if s.is_empty() => f.write_str("Arithmetic error")?,
             Self::ErrorArithmetic(s, ..) => f.write_str(s)?,
 
-            Self::LoopBreak(true, ..) => f.write_str("'break' must be inside a loop")?,
-            Self::LoopBreak(false, ..) => f.write_str("'continue' must be inside a loop")?,
+            Self::LoopBreak(true, ..) => f.write_str("'break' must be within a loop")?,
+            Self::LoopBreak(false, ..) => f.write_str("'continue' must be within a loop")?,
 
             Self::Return(..) => f.write_str("NOT AN ERROR - function returns value")?,
 
@@ -261,7 +251,7 @@ impl fmt::Display for EvalAltResult {
                 f,
                 "Bit-field index {index} out of bounds: only {max} bits in bit-field",
             )?,
-            Self::ErrorDataTooLarge(typ, ..) => write!(f, "{typ} exceeds maximum limit")?,
+            Self::ErrorDataTooLarge(typ, ..) => write!(f, "{typ} too large")?,
 
             Self::ErrorCustomSyntax(s, tokens, ..) => write!(f, "{s}: {}", tokens.join(" "))?,
         }

src/types/float.rs

@@ -15,6 +15,7 @@ use num_traits::float::FloatCore as Float;
 ///
 /// Not available under `no_float`.
 #[derive(Clone, Copy, Eq, PartialEq, PartialOrd)]
+#[must_use]
 pub struct FloatWrapper<F>(F);
 
 impl Hash for FloatWrapper<crate::FLOAT> {
@@ -108,7 +109,6 @@ impl<F: Float> FloatWrapper<F> {
 
     /// Create a new [`FloatWrapper`].
     #[inline(always)]
-    #[must_use]
     pub const fn new(value: F) -> Self {
         Self(value)
     }

src/types/fn_ptr.rs

@@ -4,8 +4,8 @@ use crate::eval::GlobalRuntimeState;
 use crate::tokenizer::is_valid_function_name;
 use crate::types::dynamic::Variant;
 use crate::{
-    reify, Dynamic, Engine, FuncArgs, ImmutableString, NativeCallContext, Position, RhaiError,
-    RhaiResult, RhaiResultOf, StaticVec, AST, ERR,
+    Dynamic, Engine, FuncArgs, ImmutableString, NativeCallContext, Position, RhaiError, RhaiResult,
+    RhaiResultOf, StaticVec, AST, ERR,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;

src/types/interner.rs

@@ -24,7 +24,6 @@ pub const MAX_STRING_LEN: usize = 24;
 /// _(internals)_ A cache for interned strings.
 /// Exported under the `internals` feature only.
 #[derive(Clone)]
-#[must_use]
 pub struct StringsInterner {
     /// Cached strings.
     cache: StraightHashMap<ImmutableString>,
@@ -34,6 +33,7 @@ pub struct StringsInterner {
 
 impl Default for StringsInterner {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }
@@ -50,6 +50,7 @@ impl fmt::Debug for StringsInterner {
 impl StringsInterner {
     /// Create a new [`StringsInterner`].
     #[inline(always)]
+    #[must_use]
     pub fn new() -> Self {
         Self {
             cache: StraightHashMap::default(),

src/types/mod.rs

@@ -1,5 +1,8 @@
 //! Module defining Rhai data types.
 
+#[macro_use]
+pub mod restore;
+
 pub mod bloom_filter;
 pub mod custom_types;
 pub mod dynamic;
@@ -9,7 +12,8 @@ pub mod fn_ptr;
 pub mod immutable_string;
 pub mod interner;
 pub mod parse_error;
-pub mod restore;
+pub mod position;
+pub mod position_none;
 pub mod scope;
 pub mod variant;
 
@@ -25,6 +29,12 @@ pub use fn_ptr::FnPtr;
 pub use immutable_string::ImmutableString;
 pub use interner::StringsInterner;
 pub use parse_error::{LexError, ParseError, ParseErrorType};
+
+#[cfg(not(feature = "no_position"))]
+pub use position::{Position, Span};
+#[cfg(feature = "no_position")]
+pub use position_none::{Position, Span};
+
 pub use restore::RestoreOnDrop;
 pub use scope::Scope;
 pub use variant::Variant;

src/types/parse_error.rs

@@ -19,7 +19,7 @@ pub enum LexError {
     UnexpectedInput(String),
     /// A string literal is not terminated before a new-line or EOF.
     UnterminatedString,
-    /// An identifier is in an invalid format.
+    /// An identifier or string literal is longer than the maximum allowed length.
     StringTooLong(usize),
     /// An string/character/numeric escape sequence is in an invalid format.
     MalformedEscapeSequence(String),
@@ -44,11 +44,7 @@ impl fmt::Display for LexError {
             Self::MalformedChar(s) => write!(f, "Invalid character: '{s}'"),
             Self::MalformedIdentifier(s) => write!(f, "Variable name is not proper: '{s}'"),
             Self::UnterminatedString => f.write_str("Open string is not terminated"),
-            Self::StringTooLong(max) => write!(
-                f,
-                "Length of string literal exceeds the maximum limit ({})",
-                max
-            ),
+            Self::StringTooLong(max) => write!(f, "String is too long (max {max})"),
             Self::ImproperSymbol(s, d) if d.is_empty() => {
                 write!(f, "Invalid symbol encountered: '{s}'")
             }
@@ -262,7 +258,7 @@ impl From<LexError> for ParseErrorType {
     fn from(err: LexError) -> Self {
         match err {
             LexError::StringTooLong(max) => {
-                Self::LiteralTooLarge("Length of string literal".to_string(), max)
+                Self::LiteralTooLarge("Length of string".to_string(), max)
             }
             _ => Self::BadInput(err),
         }

src/types/position.rs

@@ -0,0 +1,286 @@
+//! Script character position type.
+#![cfg(not(feature = "no_position"))]
+
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+use std::{
+    fmt,
+    ops::{Add, AddAssign},
+};
+
+/// A location (line number + character position) in the input script.
+///
+/// # Limitations
+///
+/// In order to keep footprint small, both line number and character position have 16-bit resolution,
+/// meaning they go up to a maximum of 65,535 lines and 65,535 characters per line.
+///
+/// Advancing beyond the maximum line length or maximum number of lines is not an error but has no effect.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
+pub struct Position {
+    /// Line number: 0 = none
+    line: u16,
+    /// Character position: 0 = BOL
+    pos: u16,
+}
+
+impl Position {
+    /// A [`Position`] representing no position.
+    pub const NONE: Self = Self { line: 0, pos: 0 };
+    /// A [`Position`] representing the first position.
+    pub const START: Self = Self { line: 1, pos: 0 };
+
+    /// Create a new [`Position`].
+    ///
+    /// `line` must not be zero.
+    ///
+    /// If `position` is zero, then it is at the beginning of a line.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `line` is zero.
+    #[inline]
+    #[must_use]
+    pub const fn new(line: u16, position: u16) -> Self {
+        assert!(line != 0, "line cannot be zero");
+
+        let _pos = position;
+
+        Self { line, pos: _pos }
+    }
+    /// Get the line number (1-based), or [`None`] if there is no position.
+    ///
+    /// Always returns [`None`] under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn line(self) -> Option<usize> {
+        if self.is_none() {
+            None
+        } else {
+            Some(self.line as usize)
+        }
+    }
+    /// Get the character position (1-based), or [`None`] if at beginning of a line.
+    ///
+    /// Always returns [`None`] under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn position(self) -> Option<usize> {
+        if self.is_none() || self.pos == 0 {
+            None
+        } else {
+            Some(self.pos as usize)
+        }
+    }
+    /// Advance by one character position.
+    #[inline]
+    pub(crate) fn advance(&mut self) {
+        assert!(!self.is_none(), "cannot advance Position::none");
+
+        // Advance up to maximum position
+        if self.pos < u16::MAX {
+            self.pos += 1;
+        }
+    }
+    /// Go backwards by one character position.
+    ///
+    /// # Panics
+    ///
+    /// Panics if already at beginning of a line - cannot rewind to a previous line.
+    #[inline]
+    pub(crate) fn rewind(&mut self) {
+        assert!(!self.is_none(), "cannot rewind Position::none");
+        assert!(self.pos > 0, "cannot rewind at position 0");
+        self.pos -= 1;
+    }
+    /// Advance to the next line.
+    #[inline]
+    pub(crate) fn new_line(&mut self) {
+        assert!(!self.is_none(), "cannot advance Position::none");
+
+        // Advance up to maximum position
+        if self.line < u16::MAX {
+            self.line += 1;
+            self.pos = 0;
+        }
+    }
+    /// Is this [`Position`] at the beginning of a line?
+    ///
+    /// Always returns `false` under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn is_beginning_of_line(self) -> bool {
+        self.pos == 0 && !self.is_none()
+    }
+    /// Is there no [`Position`]?
+    ///
+    /// Always returns `true` under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn is_none(self) -> bool {
+        self.line == 0 && self.pos == 0
+    }
+    /// Returns an fallback [`Position`] if it is [`NONE`][Position::NONE]?
+    ///
+    /// Always returns the fallback under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn or_else(self, pos: Self) -> Self {
+        if self.is_none() {
+            pos
+        } else {
+            self
+        }
+    }
+    /// Print this [`Position`] for debug purposes.
+    #[inline]
+    pub(crate) fn debug_print(self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if !self.is_none() {
+            write!(_f, " @ {:?}", self)?;
+        }
+        Ok(())
+    }
+}
+
+impl Default for Position {
+    #[inline(always)]
+    #[must_use]
+    fn default() -> Self {
+        Self::START
+    }
+}
+
+impl fmt::Display for Position {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.is_none() {
+            write!(f, "none")
+        } else {
+            write!(f, "line {}, position {}", self.line, self.pos)
+        }
+    }
+}
+
+impl fmt::Debug for Position {
+    #[cold]
+    #[inline(never)]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.is_none() {
+            f.write_str("none")
+        } else {
+            if self.is_beginning_of_line() {
+                write!(f, "{}", self.line)
+            } else {
+                write!(f, "{}:{}", self.line, self.pos)
+            }
+        }
+    }
+}
+
+impl Add for Position {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self::Output {
+        if rhs.is_none() {
+            self
+        } else {
+            Self {
+                line: self.line + rhs.line - 1,
+                pos: if rhs.is_beginning_of_line() {
+                    self.pos
+                } else {
+                    self.pos + rhs.pos - 1
+                },
+            }
+        }
+    }
+}
+
+impl AddAssign for Position {
+    fn add_assign(&mut self, rhs: Self) {
+        *self = *self + rhs;
+    }
+}
+
+/// _(internals)_ A span consisting of a starting and an ending [positions][Position].
+/// Exported under the `internals` feature only.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
+pub struct Span {
+    /// Starting [position][Position].
+    start: Position,
+    /// Ending [position][Position].
+    end: Position,
+}
+
+impl Default for Span {
+    #[inline(always)]
+    #[must_use]
+    fn default() -> Self {
+        Self::NONE
+    }
+}
+
+impl Span {
+    /// Empty [`Span`].
+    pub const NONE: Self = Self::new(Position::NONE, Position::NONE);
+
+    /// Create a new [`Span`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn new(start: Position, end: Position) -> Self {
+        Self { start, end }
+    }
+    /// Is this [`Span`] non-existent?
+    ///
+    /// Always returns `true` under `no_position`.
+    #[inline]
+    #[must_use]
+    pub const fn is_none(&self) -> bool {
+        self.start.is_none() && self.end.is_none()
+    }
+    /// Get the [`Span`]'s starting [position][Position].
+    ///
+    /// Always returns [`Position::NONE`] under `no_position`.
+    #[inline(always)]
+    #[must_use]
+    pub const fn start(&self) -> Position {
+        self.start
+    }
+    /// Get the [`Span`]'s ending [position][Position].
+    ///
+    /// Always returns [`Position::NONE`] under `no_position`.
+    #[inline(always)]
+    #[must_use]
+    pub const fn end(&self) -> Position {
+        self.end
+    }
+}
+
+impl fmt::Display for Span {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let _f = f;
+
+        match (self.start(), self.end()) {
+            (Position::NONE, Position::NONE) => write!(_f, "{:?}", Position::NONE),
+            (Position::NONE, end) => write!(_f, "..{:?}", end),
+            (start, Position::NONE) => write!(_f, "{:?}", start),
+            (start, end) if start.line() != end.line() => {
+                write!(_f, "{:?}-{:?}", start, end)
+            }
+            (start, end) => write!(
+                _f,
+                "{}:{}-{}",
+                start.line().unwrap(),
+                start.position().unwrap_or(0),
+                end.position().unwrap_or(0)
+            ),
+        }
+    }
+}
+
+impl fmt::Debug for Span {
+    #[cold]
+    #[inline(never)]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}

src/types/position_none.rs

@@ -0,0 +1,182 @@
+//! Placeholder script character position type.
+#![cfg(feature = "no_position")]
+#![allow(unused_variables)]
+
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+use std::{
+    fmt,
+    ops::{Add, AddAssign},
+};
+
+/// A location (line number + character position) in the input script.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
+pub struct Position;
+
+impl Position {
+    /// A [`Position`] representing no position.
+    pub const NONE: Self = Self;
+    /// A [`Position`] representing the first position.
+    pub const START: Self = Self;
+
+    /// Create a new [`Position`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn new(line: u16, position: u16) -> Self {
+        Self
+    }
+    /// Get the line number (1-based), or [`None`] if there is no position.
+    ///
+    /// Always returns [`None`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn line(self) -> Option<usize> {
+        None
+    }
+    /// Get the character position (1-based), or [`None`] if at beginning of a line.
+    ///
+    /// Always returns [`None`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn position(self) -> Option<usize> {
+        None
+    }
+    /// Advance by one character position.
+    #[inline(always)]
+    pub(crate) fn advance(&mut self) {}
+    /// Go backwards by one character position.
+    #[inline(always)]
+    pub(crate) fn rewind(&mut self) {}
+    /// Advance to the next line.
+    #[inline(always)]
+    pub(crate) fn new_line(&mut self) {}
+    /// Is this [`Position`] at the beginning of a line?
+    ///
+    /// Always returns `false`.
+    #[inline(always)]
+    #[must_use]
+    pub const fn is_beginning_of_line(self) -> bool {
+        false
+    }
+    /// Is there no [`Position`]?
+    ///
+    /// Always returns `true`.
+    #[inline(always)]
+    #[must_use]
+    pub const fn is_none(self) -> bool {
+        true
+    }
+    /// Returns an fallback [`Position`] if it is [`NONE`][Position::NONE]?
+    ///
+    /// Always returns the fallback.
+    #[inline(always)]
+    #[must_use]
+    pub const fn or_else(self, pos: Self) -> Self {
+        pos
+    }
+    /// Print this [`Position`] for debug purposes.
+    #[inline(always)]
+    pub(crate) fn debug_print(self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        Ok(())
+    }
+}
+
+impl Default for Position {
+    #[inline(always)]
+    #[must_use]
+    fn default() -> Self {
+        Self
+    }
+}
+
+impl fmt::Display for Position {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "none")
+    }
+}
+
+impl fmt::Debug for Position {
+    #[cold]
+    #[inline(always)]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("none")
+    }
+}
+
+impl Add for Position {
+    type Output = Self;
+
+    #[inline(always)]
+    fn add(self, rhs: Self) -> Self::Output {
+        Self
+    }
+}
+
+impl AddAssign for Position {
+    #[inline(always)]
+    fn add_assign(&mut self, rhs: Self) {}
+}
+
+/// _(internals)_ A span consisting of a starting and an ending [positions][Position].
+/// Exported under the `internals` feature only.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Copy)]
+pub struct Span;
+
+impl Default for Span {
+    #[inline(always)]
+    #[must_use]
+    fn default() -> Self {
+        Self
+    }
+}
+
+impl Span {
+    /// Empty [`Span`].
+    pub const NONE: Self = Self;
+
+    /// Create a new [`Span`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn new(start: Position, end: Position) -> Self {
+        Self
+    }
+    /// Is this [`Span`] non-existent?
+    ///
+    /// Always returns `true`.
+    #[inline(always)]
+    #[must_use]
+    pub const fn is_none(&self) -> bool {
+        true
+    }
+    /// Get the [`Span`]'s starting [position][Position].
+    ///
+    /// Always returns [`Position::NONE`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn start(&self) -> Position {
+        Position::NONE
+    }
+    /// Get the [`Span`]'s ending [position][Position].
+    ///
+    /// Always returns [`Position::NONE`].
+    #[inline(always)]
+    #[must_use]
+    pub const fn end(&self) -> Position {
+        Position::NONE
+    }
+}
+
+impl fmt::Display for Span {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let f = f;
+        write!(f, "{:?}", Position)
+    }
+}
+
+impl fmt::Debug for Span {
+    #[cold]
+    #[inline(always)]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}

src/types/restore.rs

@@ -4,6 +4,52 @@ use std::ops::{Deref, DerefMut};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
+/// Automatically restore state at the end of the scope.
+macro_rules! auto_restore {
+    (let $temp:ident = $var:ident . $prop:ident; $code:stmt) => {
+        auto_restore!(let $temp = $var.$prop; $code => move |v| v.$prop = $temp);
+    };
+    (let $temp:ident = $var:ident . $prop:ident; $code:stmt => $restore:expr) => {
+        let $temp = $var.$prop;
+        $code
+        auto_restore!($var => $restore);
+    };
+    ($var:ident => $restore:ident; let $temp:ident = $save:expr;) => {
+        auto_restore!($var => $restore; let $temp = $save; {});
+    };
+    ($var:ident if $guard:expr => $restore:ident; let $temp:ident = $save:expr;) => {
+        auto_restore!($var if $guard => $restore; let $temp = $save; {});
+    };
+    ($var:ident => $restore:ident; let $temp:ident = $save:expr; $code:stmt) => {
+        let $temp = $save;
+        $code
+        auto_restore!($var => move |v| { v.$restore($temp); });
+    };
+    ($var:ident if $guard:expr => $restore:ident; let $temp:ident = $save:expr; $code:stmt) => {
+        let $temp = $save;
+        $code
+        auto_restore!($var if $guard => move |v| { v.$restore($temp); });
+    };
+    ($var:ident => $restore:expr) => {
+        auto_restore!($var = $var => $restore);
+    };
+    ($var:ident = $value:expr => $restore:expr) => {
+        let $var = &mut *crate::types::RestoreOnDrop::lock($value, $restore);
+    };
+    ($var:ident if $guard:expr => $restore:expr) => {
+        auto_restore!($var = ($var) if $guard => $restore);
+    };
+    ($var:ident = ( $value:expr ) if $guard:expr => $restore:expr) => {
+        let mut __rx__;
+        let $var = if $guard {
+            __rx__ = crate::types::RestoreOnDrop::lock($value, $restore);
+            &mut *__rx__
+        } else {
+            &mut *$value
+        };
+    };
+}
+
 /// Run custom restoration logic upon the end of scope.
 #[must_use]
 pub struct RestoreOnDrop<'a, T: ?Sized, R: FnOnce(&mut T)> {
@@ -12,19 +58,6 @@ pub struct RestoreOnDrop<'a, T: ?Sized, R: FnOnce(&mut T)> {
 }
 
 impl<'a, T: ?Sized, R: FnOnce(&mut T)> RestoreOnDrop<'a, T, R> {
-    /// Create a new [`RestoreOnDrop`] that locks a mutable reference and runs restoration logic at
-    /// the end of scope only when `need_restore` is `true`.
-    ///
-    /// Beware that the end of scope means the end of its lifetime, not necessarily waiting until
-    /// the current block scope is exited.
-    #[inline(always)]
-    pub fn lock_if(need_restore: bool, value: &'a mut T, restore: R) -> Self {
-        Self {
-            value,
-            restore: if need_restore { Some(restore) } else { None },
-        }
-    }
-
     /// Create a new [`RestoreOnDrop`] that locks a mutable reference and runs restoration logic at
     /// the end of scope.
     ///
@@ -42,9 +75,7 @@ impl<'a, T: ?Sized, R: FnOnce(&mut T)> RestoreOnDrop<'a, T, R> {
 impl<'a, T: ?Sized, R: FnOnce(&mut T)> Drop for RestoreOnDrop<'a, T, R> {
     #[inline(always)]
     fn drop(&mut self) {
-        if let Some(restore) = self.restore.take() {
-            restore(self.value);
-        }
+        self.restore.take().unwrap()(self.value);
     }
 }
 

src/types/scope.rs

@@ -386,7 +386,7 @@ impl Scope<'_> {
     #[inline(always)]
     pub fn pop(&mut self) -> &mut Self {
         self.names.pop().expect("`Scope` must not be empty");
-        self.values.pop().expect("`Scope` must not be empty");
+        let _ = self.values.pop().expect("`Scope` must not be empty");
         self.aliases.pop().expect("`Scope` must not be empty");
         self
     }

tests/arrays.rs

@@ -21,6 +21,7 @@ fn test_arrays() -> Result<(), Box<EvalAltResult>> {
     assert_eq!(engine.eval::<INT>("let y = [1, 2, 3]; y[-1]")?, 3);
     assert_eq!(engine.eval::<INT>("let y = [1, 2, 3]; y[-3]")?, 1);
     assert!(engine.eval::<bool>("let y = [1, 2, 3]; 2 in y")?);
+    assert!(engine.eval::<bool>("let y = [1, 2, 3]; 42 !in y")?);
     assert_eq!(engine.eval::<INT>("let y = [1, 2, 3]; y += 4; y[3]")?, 4);
     assert_eq!(
         engine.eval::<INT>("let y = [1, 2, 3]; pad(y, 5, 42); len(y)")?,

tests/call_fn.rs

@@ -352,7 +352,7 @@ fn test_call_fn_events() -> Result<(), Box<EvalAltResult>> {
 
     let mut handler = Handler::new();
     assert!(!handler.scope.get_value::<bool>("state").unwrap());
-    handler.on_event("update", 999);
+    let _ = handler.on_event("update", 999);
     assert!(handler.scope.get_value::<bool>("state").unwrap());
     assert_eq!(handler.on_event("start", 999).as_int().unwrap(), 1041);
 

tests/comments.rs

@@ -75,10 +75,16 @@ fn test_comments_doc() -> Result<(), Box<EvalAltResult>> {
         ",
     )?;
 
+    #[cfg(not(feature = "no_position"))]
     assert_eq!(
         ast.iter_functions().next().unwrap().comments[0],
         "/** Hello world\n** how are you?\n**/"
     );
+    #[cfg(feature = "no_position")]
+    assert_eq!(
+        ast.iter_functions().next().unwrap().comments[0],
+        "/** Hello world\n            ** how are you?\n            **/",
+    );
 
     assert!(engine
         .compile(

tests/data_size.rs

@@ -17,7 +17,7 @@ fn test_max_string_size() -> Result<(), Box<EvalAltResult>> {
             .compile(r#"let x = "hello, world!";"#)
             .expect_err("should error")
             .err_type(),
-        ParseErrorType::LiteralTooLarge("Length of string literal".to_string(), 10)
+        ParseErrorType::LiteralTooLarge("Length of string".to_string(), 10)
     );
 
     assert_eq!(
@@ -25,7 +25,7 @@ fn test_max_string_size() -> Result<(), Box<EvalAltResult>> {
             .compile(r#"let x = "朝に紅顔、暮に白骨";"#)
             .expect_err("should error")
             .err_type(),
-        ParseErrorType::LiteralTooLarge("Length of string literal".to_string(), 10)
+        ParseErrorType::LiteralTooLarge("Length of string".to_string(), 10)
     );
 
     assert!(matches!(

tests/debugging.rs

@@ -12,7 +12,7 @@ fn test_debugging() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     engine.register_debugger(
-        |_| Dynamic::UNIT,
+        |_, dbg| dbg,
         |_, _, _, _, _| Ok(rhai::debugger::DebuggerCommand::Continue),
     );
 
@@ -47,19 +47,20 @@ fn test_debugger_state() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     engine.register_debugger(
-        |_| {
+        |_, mut debugger| {
             // Say, use an object map for the debugger state
             let mut state = Map::new();
             // Initialize properties
             state.insert("hello".into(), (42 as INT).into());
             state.insert("foo".into(), false.into());
-            Dynamic::from_map(state)
+            debugger.set_state(state);
+            debugger
         },
         |mut context, _, _, _, _| {
             // Print debugger state - which is an object map
             println!(
                 "Current state = {}",
-                context.global_runtime_state_mut().debugger().state()
+                context.global_runtime_state().debugger().state()
             );
 
             // Modify state

tests/looping.rs

@@ -34,6 +34,15 @@ fn test_loop() -> Result<(), Box<EvalAltResult>> {
         ParseErrorType::LoopBreak
     );
 
+    #[cfg(not(feature = "no_function"))]
+    assert_eq!(
+        *engine
+            .compile("loop { let f = || { break;  } }")
+            .expect_err("should error")
+            .err_type(),
+        ParseErrorType::LoopBreak
+    );
+
     assert_eq!(
         *engine
             .compile("let x = 0; if x > 0 { continue; }")