diff --git a/Cargo.toml b/Cargo.toml
index e93cc307..f0a66805 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -98,10 +98,10 @@ features = ["maths"]
 optional = true
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
-instant = { version = "0.1" } # WASM implementation of std::time::Instant
+instant = { version = "0.1.10" } # WASM implementation of std::time::Instant
 
 [target.'cfg(target_arch = "wasm64")'.dependencies]
-instant = { version = "0.1" } # WASM implementation of std::time::Instant
+instant = { version = "0.1.10" } # WASM implementation of std::time::Instant
 
 [package.metadata.docs.rs]
 features = ["metadata", "serde", "internals", "decimal"] # compiling for no-std
diff --git a/no_std/no_std_repl/Cargo.toml b/no_std/no_std_repl/Cargo.toml
deleted file mode 100644
index 36e9c2f0..00000000
--- a/no_std/no_std_repl/Cargo.toml
+++ /dev/null
@@ -1,38 +0,0 @@
-cargo-features = ["named-profiles"]
-
-[workspace]
-
-[package]
-name = "no_std_repl"
-version = "0.1.0"
-edition = "2018"
-authors = ["Stephen Chung"]
-description = "no-std REPL application"
-homepage = "https://github.com/rhaiscript/rhai/tree/no_std/no_std_repl"
-repository = "https://github.com/rhaiscript/rhai"
-
-[dependencies]
-rhai = { path = "../../", default_features = false, features = [ "no_std", "decimal", "metadata" ] }
-wee_alloc = { version = "0.4.5", default_features = false }
-
-[profile.dev]
-panic = "abort"
-
-[profile.release]
-opt-level = "z"             # optimize for size
-debug = false
-rpath = false
-debug-assertions = false
-codegen-units = 1
-panic = "abort"
-
-[profile.unix]
-inherits = "release"
-lto = true
-
-[profile.windows]
-inherits = "release"
-
-[profile.macos]
-inherits = "release"
-lto = "fat"
diff --git a/no_std/no_std_repl/README.md b/no_std/no_std_repl/README.md
deleted file mode 100644
index c7ea3ce5..00000000
--- a/no_std/no_std_repl/README.md
+++ /dev/null
@@ -1,26 +0,0 @@
-`no-std` REPL Sample
-====================
-
-This sample application is the same version as the `rhai-repl` tool, compiled for `no-std`.
-
-[`wee_alloc`](https://crates.io/crates/wee_alloc) is used as the allocator.
-
-
-To Build
---------
-
-The nightly compiler is required:
-
-```bash
-cargo +nightly build --release
-```
-
-A specific profile can also be used:
-
-```bash
-cargo +nightly build --profile unix -Z unstable-options
-```
-
-Three profiles are defined: `unix`, `windows` and `macos`.
-
-The release build is optimized for size.  It can be changed to optimize on speed instead.
diff --git a/no_std/no_std_repl/src/main.rs b/no_std/no_std_repl/src/main.rs
deleted file mode 100644
index 9a4b5e7f..00000000
--- a/no_std/no_std_repl/src/main.rs
+++ /dev/null
@@ -1,214 +0,0 @@
-use rhai::{Dynamic, Engine, EvalAltResult, Scope, AST};
-
-use std::{
-    env,
-    io::{stdin, stdout, Write},
-};
-
-/// Pretty-print error.
-fn print_error(input: &str, mut err: EvalAltResult) {
-    let lines: Vec<_> = input.trim().split('\n').collect();
-    let pos = err.take_position();
-
-    let line_no = if lines.len() > 1 {
-        if pos.is_none() {
-            "".to_string()
-        } else {
-            format!("{}: ", pos.line().unwrap())
-        }
-    } else {
-        "".to_string()
-    };
-
-    // Print error position
-    if pos.is_none() {
-        // No position
-        println!("{}", err);
-    } else {
-        // Specific position - print line text
-        println!("{}{}", line_no, lines[pos.line().unwrap() - 1]);
-
-        // Display position marker
-        println!(
-            "{0:>1$} {2}",
-            "^",
-            line_no.len() + pos.position().unwrap(),
-            err
-        );
-    }
-}
-
-/// Print help text.
-fn print_help() {
-    println!("help       => print this help");
-    println!("quit, exit => quit");
-    println!("scope      => print all variables in the scope");
-    println!("functions  => print all functions defined");
-    println!("json       => output all functions in JSON format");
-    println!("ast        => print the last AST (optimized)");
-    println!("astu       => print the last raw, un-optimized AST");
-    println!(r"end a line with '\' to continue to the next line.");
-    println!();
-}
-
-fn main() {
-    let title = format!("Rhai REPL tool (version {})", env!("CARGO_PKG_VERSION"));
-    println!("{}", title);
-    println!("{0:=<1$}", "", title.len());
-    print_help();
-
-    // Initialize scripting engine
-    let mut engine = Engine::new();
-
-    // Setup Engine
-    #[cfg(not(feature = "no_optimize"))]
-    engine.set_optimization_level(rhai::OptimizationLevel::None);
-
-    // Make Engine immutable
-    let engine = engine;
-
-    // Create scope
-    let mut scope = Scope::new();
-
-    // REPL loop
-    let mut input = String::new();
-    let mut main_ast: AST = Default::default();
-    let mut ast_u: AST = Default::default();
-    let mut ast: AST = Default::default();
-
-    'main_loop: loop {
-        print!("rhai-repl> ");
-        stdout().flush().expect("couldn't flush stdout");
-
-        input.clear();
-
-        loop {
-            match stdin().read_line(&mut input) {
-                Ok(0) => break 'main_loop,
-                Ok(_) => (),
-                Err(err) => panic!("input error: {}", err),
-            }
-
-            let line = input.as_str().trim_end();
-
-            // Allow line continuation
-            if line.ends_with('\\') {
-                let len = line.len();
-                input.truncate(len - 1);
-                input.push('\n');
-            } else {
-                break;
-            }
-
-            print!("> ");
-            stdout().flush().expect("couldn't flush stdout");
-        }
-
-        let script = input.trim();
-
-        if script.is_empty() {
-            continue;
-        }
-
-        // Implement standard commands
-        match script {
-            "help" => {
-                print_help();
-                continue;
-            }
-            "exit" | "quit" => break, // quit
-            "scope" => {
-                scope
-                    .iter_raw()
-                    .enumerate()
-                    .for_each(|(i, (name, constant, value))| {
-                        #[cfg(not(feature = "no_closure"))]
-                        let value_is_shared = if value.is_shared() { " (shared" } else { "" };
-                        #[cfg(feature = "no_closure")]
-                        let value_is_shared = "";
-
-                        println!(
-                            "[{}] {}{}{} = {:?}",
-                            i + 1,
-                            if constant { "const " } else { "" },
-                            name,
-                            value_is_shared,
-                            *value.read_lock::<Dynamic>().unwrap(),
-                        )
-                    });
-                println!();
-                continue;
-            }
-            "astu" => {
-                // print the last un-optimized AST
-                println!("{:#?}\n", ast_u);
-                continue;
-            }
-            "ast" => {
-                // print the last AST
-                println!("{:#?}\n", ast);
-                continue;
-            }
-            "functions" => {
-                // print a list of all registered functions
-                engine
-                    .gen_fn_signatures(false)
-                    .into_iter()
-                    .for_each(|f| println!("{}", f));
-
-                #[cfg(not(feature = "no_function"))]
-                main_ast.iter_functions().for_each(|f| println!("{}", f));
-
-                println!();
-                continue;
-            }
-            "json" => {
-                println!(
-                    "{}",
-                    engine
-                        .gen_fn_metadata_with_ast_to_json(&main_ast, true)
-                        .unwrap()
-                );
-                continue;
-            }
-            _ => (),
-        }
-
-        match engine
-            .compile_with_scope(&scope, &script)
-            .map_err(Into::into)
-            .and_then(|r| {
-                ast_u = r.clone();
-
-                #[cfg(not(feature = "no_optimize"))]
-                {
-                    ast = engine.optimize_ast(&scope, r, rhai::OptimizationLevel::Simple);
-                }
-
-                #[cfg(feature = "no_optimize")]
-                {
-                    ast = r;
-                }
-
-                // Merge the AST into the main
-                main_ast += ast.clone();
-
-                // Evaluate
-                engine.eval_ast_with_scope::<Dynamic>(&mut scope, &main_ast)
-            }) {
-            Ok(result) if !result.is::<()>() => {
-                println!("=> {:?}", result);
-                println!();
-            }
-            Ok(_) => (),
-            Err(err) => {
-                println!();
-                print_error(&input, *err);
-                println!();
-            }
-        }
-
-        // Throw away all the statements, leaving only the functions
-        main_ast.clear_statements();
-    }
-}
diff --git a/src/ast.rs b/src/ast.rs
index c9ce1d3f..16288c17 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -40,7 +40,7 @@ pub enum FnAccess {
     Private,
 }
 
-/// _(INTERNALS)_ A type containing information on a scripted function.
+/// _(internals)_ A type containing information on a scripted function.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -68,7 +68,7 @@ pub struct ScriptFnDef {
     /// Not available under `no_closure`.
     #[cfg(not(feature = "no_closure"))]
     pub externals: std::collections::BTreeSet<Identifier>,
-    /// _(METADATA)_ Function doc-comments (if any).
+    /// _(metadata)_ Function doc-comments (if any).
     /// Exported under the `metadata` feature only.
     ///
     /// Not available under `no_function`.
@@ -104,7 +104,7 @@ impl fmt::Display for ScriptFnDef {
 #[cfg(not(feature = "no_function"))]
 #[derive(Debug, Eq, PartialEq, Clone, Hash)]
 pub struct ScriptFnMetadata<'a> {
-    /// _(METADATA)_ Function doc-comments (if any).
+    /// _(metadata)_ Function doc-comments (if any).
     /// Exported under the `metadata` feature only.
     ///
     /// Not available under `no_function`.
@@ -278,7 +278,7 @@ impl AST {
     pub(crate) fn statements(&self) -> &[Stmt] {
         &self.body.0
     }
-    /// _(INTERNALS)_ Get the statements.
+    /// _(internals)_ Get the statements.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[deprecated = "this method is volatile and may change"]
@@ -303,7 +303,7 @@ impl AST {
     pub(crate) fn shared_lib(&self) -> Shared<Module> {
         self.functions.clone()
     }
-    /// _(INTERNALS)_ Get the internal shared [`Module`] containing all script-defined functions.
+    /// _(internals)_ Get the internal shared [`Module`] containing all script-defined functions.
     /// Exported under the `internals` feature only.
     ///
     /// Not available under `no_function` or `no_module`.
@@ -323,7 +323,7 @@ impl AST {
     pub(crate) fn lib(&self) -> &Module {
         &self.functions
     }
-    /// _(INTERNALS)_ Get the internal [`Module`] containing all script-defined functions.
+    /// _(internals)_ Get the internal [`Module`] containing all script-defined functions.
     /// Exported under the `internals` feature only.
     ///
     /// Not available under `no_function`.
@@ -344,7 +344,7 @@ impl AST {
     ) -> Option<Shared<crate::module::resolvers::StaticModuleResolver>> {
         self.resolver.clone()
     }
-    /// _(INTERNALS)_ Get the embedded [module resolver][crate::ModuleResolver].
+    /// _(internals)_ Get the embedded [module resolver][crate::ModuleResolver].
     /// Exported under the `internals` feature only.
     ///
     /// Not available under `no_module`.
@@ -762,7 +762,7 @@ impl AST {
 
         true
     }
-    /// _(INTERNALS)_ Recursively walk the [`AST`], including function bodies (if any).
+    /// _(internals)_ Recursively walk the [`AST`], including function bodies (if any).
     /// Return `false` from the callback to terminate the walk.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
@@ -816,7 +816,7 @@ impl AsRef<Module> for AST {
     }
 }
 
-/// _(INTERNALS)_ An identifier containing a name and a [position][Position].
+/// _(internals)_ An identifier containing a name and a [position][Position].
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -837,7 +837,7 @@ impl fmt::Debug for Ident {
     }
 }
 
-/// _(INTERNALS)_ A type encapsulating the mode of a `return`/`throw` statement.
+/// _(internals)_ A type encapsulating the mode of a `return`/`throw` statement.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -851,7 +851,7 @@ pub enum ReturnType {
     Exception,
 }
 
-/// _(INTERNALS)_ An [`AST`] node, consisting of either an [`Expr`] or a [`Stmt`].
+/// _(internals)_ An [`AST`] node, consisting of either an [`Expr`] or a [`Stmt`].
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -875,7 +875,7 @@ impl<'a> From<&'a Expr> for ASTNode<'a> {
     }
 }
 
-/// _(INTERNALS)_ A statements block.
+/// _(internals)_ A statements block.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -950,7 +950,19 @@ impl From<StmtBlock> for Stmt {
     }
 }
 
-/// _(INTERNALS)_ A statement.
+/// _(internals)_ Type of variable declaration.
+/// Exported under the `internals` feature only.
+///
+/// # Volatile Data Structure
+///
+/// This type is volatile and may change.
+#[derive(Debug, Eq, PartialEq, Copy, Clone, Hash)]
+pub enum VarDeclaration {
+    Let,
+    Const,
+}
+
+/// _(internals)_ A statement.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -974,10 +986,8 @@ pub enum Stmt {
     Do(Box<StmtBlock>, Expr, bool, Position),
     /// `for` `(` id `,` counter `)` `in` expr `{` stmt `}`
     For(Expr, Box<(Ident, Option<Ident>, StmtBlock)>, Position),
-    /// \[`export`\] `let` id `=` expr
-    Let(Expr, Box<Ident>, bool, Position),
-    /// \[`export`\] `const` id `=` expr
-    Const(Expr, Box<Ident>, bool, Position),
+    /// \[`export`\] `let`/`const` id `=` expr
+    Var(Expr, Box<Ident>, VarDeclaration, bool, Position),
     /// expr op`=` expr
     Assignment(Box<(Expr, Option<OpAssignment<'static>>, Expr)>, Position),
     /// func `(` expr `,` ... `)`
@@ -1058,8 +1068,7 @@ impl Stmt {
             | Self::Do(_, _, _, pos)
             | Self::For(_, _, pos)
             | Self::Return(_, _, pos)
-            | Self::Let(_, _, _, pos)
-            | Self::Const(_, _, _, pos)
+            | Self::Var(_, _, _, _, pos)
             | Self::TryCatch(_, pos) => *pos,
 
             Self::Expr(x) => x.position(),
@@ -1088,8 +1097,7 @@ impl Stmt {
             | Self::Do(_, _, _, pos)
             | Self::For(_, _, pos)
             | Self::Return(_, _, pos)
-            | Self::Let(_, _, _, pos)
-            | Self::Const(_, _, _, pos)
+            | Self::Var(_, _, _, _, pos)
             | Self::TryCatch(_, pos) => *pos = new_pos,
 
             Self::Expr(x) => {
@@ -1123,8 +1131,7 @@ impl Stmt {
             | Self::For(_, _, _)
             | Self::TryCatch(_, _) => false,
 
-            Self::Let(_, _, _, _)
-            | Self::Const(_, _, _, _)
+            Self::Var(_, _, _, _, _)
             | Self::Assignment(_, _)
             | Self::Continue(_)
             | Self::Break(_)
@@ -1151,8 +1158,7 @@ impl Stmt {
             // A No-op requires a semicolon in order to know it is an empty statement!
             Self::Noop(_) => false,
 
-            Self::Let(_, _, _, _)
-            | Self::Const(_, _, _, _)
+            Self::Var(_, _, _, _, _)
             | Self::Assignment(_, _)
             | Self::FnCall(_, _)
             | Self::Expr(_)
@@ -1193,10 +1199,7 @@ impl Stmt {
                 condition.is_pure() && block.0.iter().all(Stmt::is_pure)
             }
             Self::For(iterable, x, _) => iterable.is_pure() && (x.2).0.iter().all(Stmt::is_pure),
-            Self::Let(_, _, _, _)
-            | Self::Const(_, _, _, _)
-            | Self::Assignment(_, _)
-            | Self::FnCall(_, _) => false,
+            Self::Var(_, _, _, _, _) | Self::Assignment(_, _) | Self::FnCall(_, _) => false,
             Self::Block(block, _) => block.iter().all(|stmt| stmt.is_pure()),
             Self::Continue(_) | Self::Break(_) | Self::Return(_, _, _) => false,
             Self::TryCatch(x, _) => {
@@ -1222,7 +1225,7 @@ impl Stmt {
     #[must_use]
     pub fn is_internally_pure(&self) -> bool {
         match self {
-            Self::Let(expr, _, _, _) | Self::Const(expr, _, _, _) => expr.is_pure(),
+            Self::Var(expr, _, _, _, _) => expr.is_pure(),
 
             #[cfg(not(feature = "no_module"))]
             Self::Import(expr, _, _) => expr.is_pure(),
@@ -1260,7 +1263,7 @@ impl Stmt {
         }
 
         match self {
-            Self::Let(e, _, _, _) | Self::Const(e, _, _, _) => {
+            Self::Var(e, _, _, _, _) => {
                 if !e.walk(path, on_node) {
                     return false;
                 }
@@ -1375,7 +1378,7 @@ impl Stmt {
     }
 }
 
-/// _(INTERNALS)_ A custom syntax expression.
+/// _(internals)_ A custom syntax expression.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1391,7 +1394,7 @@ pub struct CustomExpr {
     pub tokens: StaticVec<Identifier>,
 }
 
-/// _(INTERNALS)_ A binary expression.
+/// _(internals)_ A binary expression.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1405,7 +1408,7 @@ pub struct BinaryExpr {
     pub rhs: Expr,
 }
 
-/// _(INTERNALS)_ An op-assignment operator.
+/// _(internals)_ An op-assignment operator.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1443,7 +1446,7 @@ impl OpAssignment<'_> {
     }
 }
 
-/// _(INTERNALS)_ An set of function call hashes.
+/// _(internals)_ An set of function call hashes.
 /// Exported under the `internals` feature only.
 ///
 /// Two separate hashes are pre-calculated because of the following pattern:
@@ -1530,7 +1533,7 @@ impl FnCallHashes {
     }
 }
 
-/// _(INTERNALS)_ A function call.
+/// _(internals)_ A function call.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1686,7 +1689,7 @@ impl FloatWrapper<FLOAT> {
     }
 }
 
-/// _(INTERNALS)_ An expression sub-tree.
+/// _(internals)_ An expression sub-tree.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
diff --git a/src/dynamic.rs b/src/dynamic.rs
index 512e062d..8441a940 100644
--- a/src/dynamic.rs
+++ b/src/dynamic.rs
@@ -46,7 +46,7 @@ mod private {
     impl<T: Any + Clone + SendSync> Sealed for T {}
 }
 
-/// _(INTERNALS)_ Trait to represent any type.
+/// _(internals)_ Trait to represent any type.
 /// Exported under the `internals` feature only.
 ///
 /// This trait is sealed and cannot be implemented.
@@ -80,7 +80,7 @@ pub trait Variant: Any + private::Sealed {
     fn clone_into_dynamic(&self) -> Dynamic;
 }
 
-/// _(INTERNALS)_ Trait to represent any type.
+/// _(internals)_ Trait to represent any type.
 /// Exported under the `internals` feature only.
 ///
 /// This trait is sealed and cannot be implemented.
@@ -189,7 +189,7 @@ pub enum Union {
     /// Not available under `no_float`.
     #[cfg(not(feature = "no_float"))]
     Float(FloatWrapper<FLOAT>, Tag, AccessMode),
-    /// _(DECIMAL)_ A fixed-precision decimal value.
+    /// _(decimal)_ A fixed-precision decimal value.
     /// Exported under the `decimal` feature only.
     #[cfg(feature = "decimal")]
     Decimal(Box<Decimal>, Tag, AccessMode),
@@ -222,7 +222,7 @@ pub enum Union {
     Shared(crate::Shared<crate::Locked<Dynamic>>, Tag, AccessMode),
 }
 
-/// _(INTERNALS)_ Lock guard for reading a [`Dynamic`].
+/// _(internals)_ Lock guard for reading a [`Dynamic`].
 /// Exported under the `internals` feature only.
 ///
 /// This type provides transparent interoperability between normal [`Dynamic`] and shared
@@ -265,7 +265,7 @@ impl<'d, T: Any + Clone> Deref for DynamicReadLock<'d, T> {
     }
 }
 
-/// _(INTERNALS)_ Lock guard for writing a [`Dynamic`].
+/// _(internals)_ Lock guard for writing a [`Dynamic`].
 /// Exported under the `internals` feature only.
 ///
 /// This type provides transparent interoperability between normal [`Dynamic`] and shared
@@ -1762,7 +1762,7 @@ impl Dynamic {
             _ => Err(self.type_name()),
         }
     }
-    /// _(DECIMAL)_ Cast the [`Dynamic`] as a [`Decimal`] and return it.
+    /// _(decimal)_ Cast the [`Dynamic`] as a [`Decimal`](https://docs.rs/rust_decimal) and return it.
     /// Returns the name of the actual type if the cast fails.
     ///
     /// Exported under the `decimal` feature only.
diff --git a/src/engine.rs b/src/engine.rs
index 75924308..8bd29996 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -1,6 +1,6 @@
 //! Main module defining the script evaluation [`Engine`].
 
-use crate::ast::{Expr, FnCallExpr, Ident, OpAssignment, ReturnType, Stmt};
+use crate::ast::{Expr, FnCallExpr, Ident, OpAssignment, ReturnType, Stmt, VarDeclaration};
 use crate::custom_syntax::CustomSyntax;
 use crate::dynamic::{map_std_type_name, AccessMode, Union, Variant};
 use crate::fn_hash::get_hasher;
@@ -40,7 +40,7 @@ use crate::ast::FnCallHashes;
 
 pub type Precedence = NonZeroU8;
 
-/// _(INTERNALS)_ A stack of imported [modules][Module].
+/// _(internals)_ A stack of imported [modules][Module].
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -620,7 +620,7 @@ impl<T: Into<Dynamic>> From<T> for Target<'_> {
     }
 }
 
-/// _(INTERNALS)_ An entry in a function resolution cache.
+/// _(internals)_ An entry in a function resolution cache.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -634,7 +634,7 @@ pub struct FnResolutionCacheEntry {
     pub source: Option<Identifier>,
 }
 
-/// _(INTERNALS)_ A function resolution cache.
+/// _(internals)_ A function resolution cache.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -642,7 +642,7 @@ pub struct FnResolutionCacheEntry {
 /// This type is volatile and may change.
 pub type FnResolutionCache = BTreeMap<u64, Option<Box<FnResolutionCacheEntry>>>;
 
-/// _(INTERNALS)_ A type that holds all the current states of the [`Engine`].
+/// _(internals)_ A type that holds all the current states of the [`Engine`].
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -653,19 +653,20 @@ pub struct EvalState {
     /// Source of the current context.
     pub source: Option<Identifier>,
     /// Normally, access to variables are parsed with a relative offset into the [`Scope`] to avoid a lookup.
-    /// In some situation, e.g. after running an `eval` statement, subsequent offsets may become mis-aligned.
+    /// In some situation, e.g. after running an `eval` statement, or after a custom syntax statement,
+    /// subsequent offsets may become mis-aligned.
     /// When that happens, this flag is turned on to force a [`Scope`] search by name.
     pub always_search_scope: bool,
     /// Level of the current scope.  The global (root) level is zero, a new block (or function call)
     /// is one level higher, and so on.
     pub scope_level: usize,
     /// Number of operations performed.
-    pub operations: u64,
+    pub num_operations: u64,
     /// Number of modules loaded.
-    pub modules: usize,
+    pub num_modules: usize,
     /// Embedded module resolver.
     #[cfg(not(feature = "no_module"))]
-    pub resolver: Option<Shared<crate::module::resolvers::StaticModuleResolver>>,
+    pub embedded_module_resolver: Option<Shared<crate::module::resolvers::StaticModuleResolver>>,
     /// Stack of function resolution caches.
     fn_resolution_caches: Vec<FnResolutionCache>,
 }
@@ -679,10 +680,10 @@ impl EvalState {
             source: None,
             always_search_scope: false,
             scope_level: 0,
-            operations: 0,
-            modules: 0,
+            num_operations: 0,
+            num_modules: 0,
             #[cfg(not(feature = "no_module"))]
-            resolver: None,
+            embedded_module_resolver: None,
             fn_resolution_caches: Vec::new(),
         }
     }
@@ -723,7 +724,7 @@ impl EvalState {
     }
 }
 
-/// _(INTERNALS)_ A type containing all the limits imposed by the [`Engine`].
+/// _(internals)_ A type containing all the limits imposed by the [`Engine`].
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -833,7 +834,7 @@ impl<'x, 'px, 'pt> EvalContext<'_, 'x, 'px, '_, '_, '_, '_, 'pt> {
     pub fn iter_imports(&self) -> impl Iterator<Item = (&str, &Module)> {
         self.mods.iter()
     }
-    /// _(INTERNALS)_ The current set of modules imported via `import` statements.
+    /// _(internals)_ The current set of modules imported via `import` statements.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[cfg(not(feature = "no_module"))]
@@ -847,7 +848,7 @@ impl<'x, 'px, 'pt> EvalContext<'_, 'x, 'px, '_, '_, '_, '_, 'pt> {
     pub fn iter_namespaces(&self) -> impl Iterator<Item = &Module> {
         self.lib.iter().cloned()
     }
-    /// _(INTERNALS)_ The current set of namespaces containing definitions of all script-defined functions.
+    /// _(internals)_ The current set of namespaces containing definitions of all script-defined functions.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[inline(always)]
@@ -2850,12 +2851,11 @@ impl Engine {
             }
 
             // Let/const statement
-            Stmt::Let(expr, x, export, _) | Stmt::Const(expr, x, export, _) => {
+            Stmt::Var(expr, x, var_type, export, _) => {
                 let name = &x.name;
-                let entry_type = match stmt {
-                    Stmt::Let(_, _, _, _) => AccessMode::ReadWrite,
-                    Stmt::Const(_, _, _, _) => AccessMode::ReadOnly,
-                    _ => unreachable!("should be Stmt::Let or Stmt::Const, but gets {:?}", stmt),
+                let entry_type = match var_type {
+                    VarDeclaration::Let => AccessMode::ReadWrite,
+                    VarDeclaration::Const => AccessMode::ReadOnly,
                 };
 
                 let value = self
@@ -2914,7 +2914,7 @@ impl Engine {
             Stmt::Import(expr, export, _pos) => {
                 // Guard against too many modules
                 #[cfg(not(feature = "unchecked"))]
-                if state.modules >= self.max_modules() {
+                if state.num_modules >= self.max_modules() {
                     return EvalAltResult::ErrorTooManyModules(*_pos).into();
                 }
 
@@ -2928,7 +2928,7 @@ impl Engine {
                     let path_pos = expr.position();
 
                     let module = state
-                        .resolver
+                        .embedded_module_resolver
                         .as_ref()
                         .and_then(|r| match r.resolve(self, source, &path, path_pos) {
                             Err(err)
@@ -2958,7 +2958,7 @@ impl Engine {
                         }
                     }
 
-                    state.modules += 1;
+                    state.num_modules += 1;
 
                     Ok(Dynamic::UNIT)
                 } else {
@@ -3130,16 +3130,16 @@ impl Engine {
         state: &mut EvalState,
         pos: Position,
     ) -> Result<(), Box<EvalAltResult>> {
-        state.operations += 1;
+        state.num_operations += 1;
 
         // Guard against too many operations
-        if self.max_operations() > 0 && state.operations > self.max_operations() {
+        if self.max_operations() > 0 && state.num_operations > self.max_operations() {
             return EvalAltResult::ErrorTooManyOperations(pos).into();
         }
 
         // Report progress - only in steps
         if let Some(ref progress) = self.progress {
-            if let Some(token) = progress(state.operations) {
+            if let Some(token) = progress(state.num_operations) {
                 // Terminate script if progress returns a termination token
                 return EvalAltResult::ErrorTerminated(token, pos).into();
             }
diff --git a/src/engine_api.rs b/src/engine_api.rs
index d61c4074..99213283 100644
--- a/src/engine_api.rs
+++ b/src/engine_api.rs
@@ -1729,7 +1729,7 @@ impl Engine {
         state.source = ast.source_raw().cloned();
         #[cfg(not(feature = "no_module"))]
         {
-            state.resolver = ast.resolver();
+            state.embedded_module_resolver = ast.resolver();
         }
 
         let statements = ast.statements();
@@ -1811,7 +1811,7 @@ impl Engine {
         state.source = ast.source_raw().cloned();
         #[cfg(not(feature = "no_module"))]
         {
-            state.resolver = ast.resolver();
+            state.embedded_module_resolver = ast.resolver();
         }
 
         let statements = ast.statements();
@@ -2052,7 +2052,7 @@ impl Engine {
         let stmt = std::mem::take(ast.statements_mut());
         crate::optimize::optimize_into_ast(self, scope, stmt.into_vec(), lib, optimization_level)
     }
-    /// _(METADATA)_ Generate a list of all registered functions.
+    /// _(metadata)_ Generate a list of all registered functions.
     /// Exported under the `metadata` feature only.
     ///
     /// Functions from the following sources are included, in order:
diff --git a/src/error_parsing.rs b/src/error_parsing.rs
index c65b9b07..396c7957 100644
--- a/src/error_parsing.rs
+++ b/src/error_parsing.rs
@@ -9,7 +9,7 @@ use std::fmt;
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 
-/// _(INTERNALS)_ Error encountered when tokenizing the script text.
+/// _(internals)_ Error encountered when tokenizing the script text.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
diff --git a/src/fn_call.rs b/src/fn_call.rs
index 23bc447a..e79e906a 100644
--- a/src/fn_call.rs
+++ b/src/fn_call.rs
@@ -840,12 +840,12 @@ impl Engine {
         // Evaluate the AST
         let mut new_state = EvalState::new();
         new_state.source = state.source.clone();
-        new_state.operations = state.operations;
+        new_state.num_operations = state.num_operations;
 
         let result =
             self.eval_global_statements(scope, mods, &mut new_state, statements, lib, level);
 
-        state.operations = new_state.operations;
+        state.num_operations = new_state.num_operations;
 
         result
     }
diff --git a/src/fn_native.rs b/src/fn_native.rs
index 9930fec4..c7d8cdbd 100644
--- a/src/fn_native.rs
+++ b/src/fn_native.rs
@@ -98,7 +98,7 @@ impl<'a> NativeCallContext<'a> {
             lib,
         }
     }
-    /// _(INTERNALS)_ Create a new [`NativeCallContext`].
+    /// _(internals)_ Create a new [`NativeCallContext`].
     /// Exported under the `internals` feature only.
     ///
     /// Not available under `no_module`.
@@ -156,7 +156,7 @@ impl<'a> NativeCallContext<'a> {
     ) -> impl Iterator<Item = (&crate::Identifier, &Shared<Module>)> {
         self.mods.iter().flat_map(|&m| m.iter_raw())
     }
-    /// _(INTERNALS)_ The current set of modules imported via `import` statements.
+    /// _(internals)_ The current set of modules imported via `import` statements.
     /// Exported under the `internals` feature only.
     ///
     /// Not available under `no_module`.
@@ -172,7 +172,7 @@ impl<'a> NativeCallContext<'a> {
     pub fn iter_namespaces(&self) -> impl Iterator<Item = &Module> {
         self.lib.iter().cloned()
     }
-    /// _(INTERNALS)_ The current set of namespaces containing definitions of all script-defined functions.
+    /// _(internals)_ The current set of namespaces containing definitions of all script-defined functions.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[inline(always)]
diff --git a/src/fn_register.rs b/src/fn_register.rs
index b74a93ce..cb90c62e 100644
--- a/src/fn_register.rs
+++ b/src/fn_register.rs
@@ -71,17 +71,17 @@ pub trait RegisterNativeFunction<Args, Result> {
     /// Get the type ID's of this function's parameters.
     #[must_use]
     fn param_types() -> Box<[TypeId]>;
-    /// _(METADATA)_ Get the type names of this function's parameters.
+    /// _(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]>;
-    /// _(METADATA)_ Get the type ID of this function's return value.
+    /// _(metadata)_ Get the type ID of this function's return value.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
     #[must_use]
     fn return_type() -> TypeId;
-    /// _(METADATA)_ Get the type name of this function's return value.
+    /// _(metadata)_ Get the type name of this function's return value.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
     #[must_use]
diff --git a/src/lib.rs b/src/lib.rs
index 6b13fac0..1d72720f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -228,7 +228,7 @@ pub use token::{InputStream, Token, TokenizeState, TokenizerControl, TokenizerCo
 #[deprecated = "this type is volatile and may change"]
 pub use ast::{
     ASTNode, BinaryExpr, CustomExpr, Expr, FloatWrapper, FnCallExpr, FnCallHashes, Ident,
-    OpAssignment, ReturnType, ScriptFnDef, Stmt, StmtBlock,
+    OpAssignment, ReturnType, ScriptFnDef, Stmt, StmtBlock, VarDeclaration,
 };
 
 #[cfg(feature = "internals")]
@@ -278,7 +278,7 @@ pub use module::NamespaceRef;
 #[cfg(not(feature = "internals"))]
 type StaticVec<T> = smallvec::SmallVec<[T; 4]>;
 
-/// _(INTERNALS)_ Alias to [`smallvec`](https://crates.io/crates/smallvec), which is a specialized
+/// _(internals)_ Alias to [`smallvec`](https://crates.io/crates/smallvec), which is a specialized
 /// [`Vec`] backed by a small, inline, fixed-size array when there are ≤ 4 items stored.
 /// Exported under the `internals` feature only.
 ///
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 413fad22..c9d10706 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -81,18 +81,18 @@ impl FuncInfo {
                 sig.push_str(") -> ");
                 sig.push_str(&return_type);
             } else {
-                sig.push_str(")");
+                sig.push(')');
             }
         } else {
             for x in 0..self.params {
-                sig.push_str("_");
+                sig.push('_');
                 if x < self.params - 1 {
                     sig.push_str(", ");
                 }
             }
 
             if self.func.is_script() {
-                sig.push_str(")");
+                sig.push(')');
             } else {
                 sig.push_str(") -> ?");
             }
@@ -102,7 +102,7 @@ impl FuncInfo {
     }
 }
 
-/// _(INTERNALS)_ Calculate a [`u64`] hash key from a namespace-qualified function name and
+/// _(internals)_ Calculate a [`u64`] hash key from a namespace-qualified function name and
 /// parameter types.
 /// Exported under the `internals` feature only.
 ///
@@ -366,7 +366,6 @@ impl Module {
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
     #[inline(always)]
-    #[must_use]
     pub fn gen_fn_signatures(&self) -> impl Iterator<Item = String> + '_ {
         self.functions
             .values()
@@ -630,9 +629,9 @@ impl Module {
             .map(|&name| self.identifiers.get(name))
             .collect();
 
-        self.functions
-            .get_mut(&hash_fn)
-            .map(|f| f.param_names = param_names);
+        if let Some(f) = self.functions.get_mut(&hash_fn) {
+            f.param_names = param_names;
+        }
 
         self
     }
@@ -1364,7 +1363,7 @@ impl Module {
             .map(|f| (f.namespace, f.access, f.name.as_str(), f.params))
     }
 
-    /// _(INTERNALS)_ Get an iterator over all script-defined functions in the [`Module`].
+    /// _(internals)_ Get an iterator over all script-defined functions in the [`Module`].
     /// Exported under the `internals` feature only.
     ///
     /// Function metadata includes:
@@ -1372,7 +1371,7 @@ impl Module {
     /// 2) Access mode ([`FnAccess::Public`] or [`FnAccess::Private`]).
     /// 3) Function name (as string slice).
     /// 4) Number of parameters.
-    /// 5) _(INTERNALS)_ Shared reference to function definition [`ScriptFnDef`][crate::ast::ScriptFnDef].
+    /// 5) _(internals)_ Shared reference to function definition [`ScriptFnDef`][crate::ast::ScriptFnDef].
     #[cfg(not(feature = "no_function"))]
     #[cfg(feature = "internals")]
     #[inline(always)]
@@ -1653,7 +1652,7 @@ impl Module {
     }
 }
 
-/// _(INTERNALS)_ A chain of [module][Module] names to namespace-qualify a variable or function call.
+/// _(internals)_ A chain of [module][Module] names to namespace-qualify a variable or function call.
 /// Exported under the `internals` feature only.
 ///
 /// A [`u64`] offset to the current [`Scope`][crate::Scope] is cached for quick search purposes.
diff --git a/src/module/resolvers/stat.rs b/src/module/resolvers/stat.rs
index 0b43bd28..0b555884 100644
--- a/src/module/resolvers/stat.rs
+++ b/src/module/resolvers/stat.rs
@@ -1,4 +1,6 @@
-use crate::{Engine, EvalAltResult, Identifier, Module, ModuleResolver, Position, Shared};
+use crate::{
+    Engine, EvalAltResult, Identifier, Module, ModuleResolver, Position, Shared, SmartString,
+};
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
 use std::{collections::BTreeMap, ops::AddAssign};
@@ -72,11 +74,6 @@ impl StaticModuleResolver {
     pub fn iter_mut(&mut self) -> impl Iterator<Item = (&str, &mut Shared<Module>)> {
         self.0.iter_mut().map(|(k, v)| (k.as_str(), v))
     }
-    /// Get a mutable iterator of all the modules.
-    #[inline(always)]
-    pub fn into_iter(self) -> impl Iterator<Item = (Identifier, Shared<Module>)> {
-        self.0.into_iter()
-    }
     /// Get an iterator of all the [module][Module] paths.
     #[inline(always)]
     pub fn paths(&self) -> impl Iterator<Item = &str> {
@@ -117,6 +114,15 @@ impl StaticModuleResolver {
     }
 }
 
+impl IntoIterator for StaticModuleResolver {
+    type Item = (Identifier, Shared<Module>);
+    type IntoIter = std::collections::btree_map::IntoIter<SmartString, Shared<Module>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
 impl ModuleResolver for StaticModuleResolver {
     #[inline(always)]
     fn resolve(
diff --git a/src/optimize.rs b/src/optimize.rs
index b5d25a9b..75fe9a83 100644
--- a/src/optimize.rs
+++ b/src/optimize.rs
@@ -1,6 +1,6 @@
 //! Module implementing the [`AST`] optimizer.
 
-use crate::ast::{Expr, OpAssignment, Stmt};
+use crate::ast::{Expr, OpAssignment, Stmt, VarDeclaration};
 use crate::dynamic::AccessMode;
 use crate::engine::{KEYWORD_DEBUG, KEYWORD_EVAL, KEYWORD_FN_PTR, KEYWORD_PRINT, KEYWORD_TYPE_OF};
 use crate::fn_builtin::get_builtin_binary_op_fn;
@@ -202,7 +202,7 @@ fn optimize_stmt_block(
         statements.iter_mut().for_each(|stmt| {
             match stmt {
                 // Add constant literals into the state
-                Stmt::Const(value_expr, x, _, _) => {
+                Stmt::Var(value_expr, x, VarDeclaration::Const, _, _) => {
                     optimize_expr(value_expr, state, false);
 
                     if value_expr.is_constant() {
@@ -214,7 +214,7 @@ fn optimize_stmt_block(
                     }
                 }
                 // Add variables into the state
-                Stmt::Let(value_expr, x, _, _) => {
+                Stmt::Var(value_expr, x, VarDeclaration::Let, _, _) => {
                     optimize_expr(value_expr, state, false);
                     state.push_var(&x.name, AccessMode::ReadWrite, None);
                 }
@@ -232,11 +232,7 @@ fn optimize_stmt_block(
             .find_map(|(i, stmt)| match stmt {
                 stmt if !is_pure(stmt) => Some(i),
 
-                Stmt::Let(e, _, _, _) | Stmt::Const(e, _, _, _) | Stmt::Expr(e)
-                    if !e.is_constant() =>
-                {
-                    Some(i)
-                }
+                Stmt::Var(e, _, _, _, _) | Stmt::Expr(e) if !e.is_constant() => Some(i),
 
                 #[cfg(not(feature = "no_module"))]
                 Stmt::Import(e, _, _) if !e.is_constant() => Some(i),
@@ -609,7 +605,7 @@ fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: b
             *x.2.statements_mut() = optimize_stmt_block(body, state, false, true, false).into();
         }
         // let id = expr;
-        Stmt::Let(expr, _, _, _) => optimize_expr(expr, state, false),
+        Stmt::Var(expr, _, VarDeclaration::Let, _, _) => optimize_expr(expr, state, false),
         // import expr as var;
         #[cfg(not(feature = "no_module"))]
         Stmt::Import(expr, _, _) => optimize_expr(expr, state, false),
diff --git a/src/parse.rs b/src/parse.rs
index 073a222f..a87ed5c8 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -2,7 +2,7 @@
 
 use crate::ast::{
     BinaryExpr, CustomExpr, Expr, FnCallExpr, FnCallHashes, Ident, OpAssignment, ReturnType,
-    ScriptFnDef, Stmt, StmtBlock,
+    ScriptFnDef, Stmt, StmtBlock, VarDeclaration,
 };
 use crate::custom_syntax::{
     CustomSyntax, CUSTOM_SYNTAX_MARKER_BLOCK, CUSTOM_SYNTAX_MARKER_BOOL, CUSTOM_SYNTAX_MARKER_EXPR,
@@ -2115,14 +2115,12 @@ fn parse_expr(
 
         match token {
             Token::Custom(key) | Token::Reserved(key) | Token::Identifier(key) => {
-                match state.engine.custom_syntax.get_key_value(key.as_str()) {
-                    Some((key, syntax)) => {
-                        input.next().expect(NEVER_ENDS);
-                        return parse_custom_syntax(
-                            input, state, lib, settings, key, syntax, token_pos,
-                        );
-                    }
-                    _ => (),
+                if let Some((key, syntax)) = state.engine.custom_syntax.get_key_value(key.as_str())
+                {
+                    input.next().expect(NEVER_ENDS);
+                    return parse_custom_syntax(
+                        input, state, lib, settings, key, syntax, token_pos,
+                    );
                 }
             }
             _ => (),
@@ -2385,9 +2383,21 @@ fn parse_let(
 
     match var_type {
         // let name = expr
-        AccessMode::ReadWrite => Ok(Stmt::Let(expr, var_def.into(), export, settings.pos)),
+        AccessMode::ReadWrite => Ok(Stmt::Var(
+            expr,
+            var_def.into(),
+            VarDeclaration::Let,
+            export,
+            settings.pos,
+        )),
         // const name = { expr:constant }
-        AccessMode::ReadOnly => Ok(Stmt::Const(expr, var_def.into(), export, settings.pos)),
+        AccessMode::ReadOnly => Ok(Stmt::Var(
+            expr,
+            var_def.into(),
+            VarDeclaration::Const,
+            export,
+            settings.pos,
+        )),
     }
 }
 
diff --git a/src/serde/de.rs b/src/serde/de.rs
index 48e7a15f..36c27e07 100644
--- a/src/serde/de.rs
+++ b/src/serde/de.rs
@@ -33,12 +33,10 @@ impl<'de> DynamicDeserializer<'de> {
         Self { value }
     }
     /// Shortcut for a type conversion error.
-    #[must_use]
     fn type_error<T>(&self) -> Result<T, Box<EvalAltResult>> {
         self.type_error_str(type_name::<T>())
     }
     /// Shortcut for a type conversion error.
-    #[must_use]
     fn type_error_str<T>(&self, error: &str) -> Result<T, Box<EvalAltResult>> {
         EvalAltResult::ErrorMismatchOutputType(
             error.into(),
@@ -47,7 +45,6 @@ impl<'de> DynamicDeserializer<'de> {
         )
         .into()
     }
-    #[must_use]
     fn deserialize_int<V: Visitor<'de>>(
         &mut self,
         v: crate::INT,
@@ -111,7 +108,6 @@ impl<'de> DynamicDeserializer<'de> {
 /// # Ok(())
 /// # }
 /// ```
-#[must_use]
 pub fn from_dynamic<'de, T: Deserialize<'de>>(
     value: &'de Dynamic,
 ) -> Result<T, Box<EvalAltResult>> {
diff --git a/src/serde/deserialize.rs b/src/serde/deserialize.rs
index b3cf6098..78bc91b6 100644
--- a/src/serde/deserialize.rs
+++ b/src/serde/deserialize.rs
@@ -40,12 +40,14 @@ impl<'d> Visitor<'d> for DynamicVisitor {
     }
     fn visit_i64<E: Error>(self, v: i64) -> Result<Self::Value, E> {
         #[cfg(not(feature = "only_i32"))]
-        return Ok(v.into());
+        {
+            Ok(v.into())
+        }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as i64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.visit_i32(v as i32);
+            self.visit_i32(v as i32)
         }
     }
     fn visit_u8<E: Error>(self, v: u8) -> Result<Self::Value, E> {
@@ -56,26 +58,28 @@ impl<'d> Visitor<'d> for DynamicVisitor {
     }
     fn visit_u32<E: Error>(self, v: u32) -> Result<Self::Value, E> {
         #[cfg(not(feature = "only_i32"))]
-        return Ok(INT::from(v).into());
+        {
+            Ok(INT::from(v).into())
+        }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as u32 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.visit_i32(v as i32);
+            self.visit_i32(v as i32)
         }
     }
     fn visit_u64<E: Error>(self, v: u64) -> Result<Self::Value, E> {
         #[cfg(not(feature = "only_i32"))]
         if v > i64::MAX as u64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.visit_i64(v as i64);
+            self.visit_i64(v as i64)
         }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as u64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.visit_i32(v as i32);
+            self.visit_i32(v as i32)
         }
     }
 
diff --git a/src/serde/metadata.rs b/src/serde/metadata.rs
index 31e04aee..9c7655f3 100644
--- a/src/serde/metadata.rs
+++ b/src/serde/metadata.rs
@@ -43,7 +43,7 @@ impl From<crate::FnAccess> for FnAccess {
     }
 }
 
-#[derive(Debug, Clone, Eq, PartialEq, Ord, Hash, Serialize, Deserialize)]
+#[derive(Debug, Clone, Eq, PartialEq, Hash, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 struct FnParam {
     pub name: String,
@@ -71,6 +71,15 @@ impl PartialOrd for FnParam {
     }
 }
 
+impl Ord for FnParam {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match self.name.cmp(&other.name) {
+            Ordering::Equal => self.typ.cmp(&other.typ),
+            cmp => cmp,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Eq, PartialEq, Hash, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 struct FnMetadata {
@@ -128,7 +137,7 @@ impl From<&crate::module::FuncInfo> for FnMetadata {
                     let name = seg
                         .next()
                         .map(|s| s.trim().to_string())
-                        .unwrap_or("_".to_string());
+                        .unwrap_or_else(|| "_".to_string());
                     let typ = seg.next().map(|s| s.trim().to_string());
                     FnParam { name, typ }
                 })
@@ -209,7 +218,7 @@ impl From<&crate::Module> for ModuleMetadata {
 
 #[cfg(feature = "metadata")]
 impl Engine {
-    /// _(METADATA)_ Generate a list of all functions (including those defined in an
+    /// _(metadata)_ Generate a list of all functions (including those defined in an
     /// [`AST`][crate::AST]) in JSON format.
     /// Exported under the `metadata` feature only.
     ///
@@ -218,7 +227,6 @@ impl Engine {
     /// 2) Functions registered into the global namespace
     /// 3) Functions in static modules
     /// 4) Functions in global modules (optional)
-    #[must_use]
     pub fn gen_fn_metadata_with_ast_to_json(
         &self,
         ast: &AST,
@@ -258,7 +266,6 @@ impl Engine {
     /// 1) Functions registered into the global namespace
     /// 2) Functions in static modules
     /// 3) Functions in global modules (optional)
-    #[must_use]
     pub fn gen_fn_metadata_to_json(&self, include_global: bool) -> serde_json::Result<String> {
         self.gen_fn_metadata_with_ast_to_json(&Default::default(), include_global)
     }
diff --git a/src/serde/mod.rs b/src/serde/mod.rs
index a3819556..f391d694 100644
--- a/src/serde/mod.rs
+++ b/src/serde/mod.rs
@@ -1,4 +1,4 @@
-//! _(SERDE)_ Serialization and deserialization support for [`serde`](https://crates.io/crates/serde).
+//! _(serde)_ Serialization and deserialization support for [`serde`](https://crates.io/crates/serde).
 //! Exported under the `serde` feature only.
 
 mod de;
diff --git a/src/serde/ser.rs b/src/serde/ser.rs
index 79483c06..c4b7d56f 100644
--- a/src/serde/ser.rs
+++ b/src/serde/ser.rs
@@ -82,7 +82,6 @@ impl DynamicSerializer {
 /// # Ok(())
 /// # }
 /// ```
-#[must_use]
 pub fn to_dynamic<T: Serialize>(value: T) -> RhaiResult {
     let mut s = DynamicSerializer::new(Default::default());
     value.serialize(&mut s)
@@ -138,27 +137,29 @@ impl Serializer for &mut DynamicSerializer {
 
     fn serialize_i64(self, v: i64) -> Result<Self::Ok, Box<EvalAltResult>> {
         #[cfg(not(feature = "only_i32"))]
-        return Ok(v.into());
+        {
+            Ok(v.into())
+        }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as i64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i32(v as i32);
+            self.serialize_i32(v as i32)
         }
     }
 
     fn serialize_i128(self, v: i128) -> Result<Self::Ok, Box<EvalAltResult>> {
         #[cfg(not(feature = "only_i32"))]
         if v > i64::MAX as i128 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i64(v as i64);
+            self.serialize_i64(v as i64)
         }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as i128 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i32(v as i32);
+            self.serialize_i32(v as i32)
         }
     }
 
@@ -178,42 +179,44 @@ impl Serializer for &mut DynamicSerializer {
 
     fn serialize_u32(self, v: u32) -> Result<Self::Ok, Box<EvalAltResult>> {
         #[cfg(not(feature = "only_i32"))]
-        return self.serialize_i64(i64::from(v));
+        {
+            self.serialize_i64(i64::from(v))
+        }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as u32 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i32(v as i32);
+            self.serialize_i32(v as i32)
         }
     }
 
     fn serialize_u64(self, v: u64) -> Result<Self::Ok, Box<EvalAltResult>> {
         #[cfg(not(feature = "only_i32"))]
         if v > i64::MAX as u64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i64(v as i64);
+            self.serialize_i64(v as i64)
         }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as u64 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i32(v as i32);
+            self.serialize_i32(v as i32)
         }
     }
 
     fn serialize_u128(self, v: u128) -> Result<Self::Ok, Box<EvalAltResult>> {
         #[cfg(not(feature = "only_i32"))]
         if v > i64::MAX as u128 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i64(v as i64);
+            self.serialize_i64(v as i64)
         }
         #[cfg(feature = "only_i32")]
         if v > i32::MAX as u128 {
-            return Ok(Dynamic::from(v));
+            Ok(Dynamic::from(v))
         } else {
-            return self.serialize_i32(v as i32);
+            self.serialize_i32(v as i32)
         }
     }
 
diff --git a/src/serde/str.rs b/src/serde/str.rs
index 5a275d90..81e90f8b 100644
--- a/src/serde/str.rs
+++ b/src/serde/str.rs
@@ -18,7 +18,6 @@ impl<'a> StringSliceDeserializer<'a> {
         Self { value }
     }
     /// Shortcut for a type conversion error.
-    #[must_use]
     fn type_error<T>(&self) -> Result<T, Box<EvalAltResult>> {
         EvalAltResult::ErrorMismatchOutputType(
             type_name::<T>().into(),
diff --git a/src/token.rs b/src/token.rs
index 4dcaec9a..cc425efd 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -27,7 +27,7 @@ use rust_decimal::Decimal;
 #[cfg(not(feature = "no_function"))]
 use crate::engine::KEYWORD_IS_DEF_FN;
 
-/// _(INTERNALS)_ A type containing commands to control the tokenizer.
+/// _(internals)_ A type containing commands to control the tokenizer.
 #[derive(Debug, Clone, Eq, PartialEq, Hash, Copy, Default)]
 pub struct TokenizerControlBlock {
     /// Is the current tokenizer position within an interpolated text string?
@@ -35,7 +35,7 @@ pub struct TokenizerControlBlock {
     pub is_within_text: bool,
 }
 
-/// _(INTERNALS)_ A shared object that allows control of the tokenizer from outside.
+/// _(internals)_ A shared object that allows control of the tokenizer from outside.
 pub type TokenizerControl = Rc<Cell<TokenizerControlBlock>>;
 
 type LERR = LexError;
@@ -283,7 +283,7 @@ impl AddAssign for Position {
     }
 }
 
-/// _(INTERNALS)_ A Rhai language token.
+/// _(internals)_ A Rhai language token.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -980,7 +980,7 @@ impl From<Token> for String {
     }
 }
 
-/// _(INTERNALS)_ State of the tokenizer.
+/// _(internals)_ State of the tokenizer.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1000,7 +1000,7 @@ pub struct TokenizeState {
     pub is_within_text_terminated_by: Option<char>,
 }
 
-/// _(INTERNALS)_ Trait that encapsulates a peekable character input stream.
+/// _(internals)_ Trait that encapsulates a peekable character input stream.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile Data Structure
@@ -1018,7 +1018,7 @@ pub trait InputStream {
     fn peek_next(&mut self) -> Option<char>;
 }
 
-/// _(INTERNALS)_ Parse a string literal ended by `termination_char`.
+/// _(internals)_ Parse a string literal ended by `termination_char`.
 /// Exported under the `internals` feature only.
 ///
 /// Returns the parsed string and a boolean indicating whether the string is
@@ -1281,22 +1281,22 @@ fn scan_block_comment(
 
         match c {
             '/' => {
-                stream.peek_next().filter(|&c2| c2 == '*').map(|c2| {
+                if let Some(c2) = stream.peek_next().filter(|&c2| c2 == '*') {
                     eat_next(stream, pos);
                     if let Some(comment) = comment.as_mut() {
                         comment.push(c2);
                     }
                     level += 1;
-                });
+                }
             }
             '*' => {
-                stream.peek_next().filter(|&c2| c2 == '/').map(|c2| {
+                if let Some(c2) = stream.peek_next().filter(|&c2| c2 == '/') {
                     eat_next(stream, pos);
                     if let Some(comment) = comment.as_mut() {
                         comment.push(c2);
                     }
                     level -= 1;
-                });
+                }
             }
             '\n' => pos.new_line(),
             _ => (),
@@ -1310,7 +1310,7 @@ fn scan_block_comment(
     level
 }
 
-/// _(INTERNALS)_ Get the next token from the `stream`.
+/// _(internals)_ Get the next token from the `stream`.
 /// Exported under the `internals` feature only.
 ///
 /// # Volatile API
@@ -2234,7 +2234,7 @@ impl<'a> Iterator for TokenIterator<'a> {
 impl FusedIterator for TokenIterator<'_> {}
 
 impl Engine {
-    /// _(INTERNALS)_ Tokenize an input text stream.
+    /// _(internals)_ Tokenize an input text stream.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[inline(always)]
@@ -2245,7 +2245,7 @@ impl Engine {
     ) -> (TokenIterator<'a>, TokenizerControl) {
         self.lex_raw(input, None)
     }
-    /// _(INTERNALS)_ Tokenize an input text stream with a mapping function.
+    /// _(internals)_ Tokenize an input text stream with a mapping function.
     /// Exported under the `internals` feature only.
     #[cfg(feature = "internals")]
     #[inline(always)]
diff --git a/tests/optimizer.rs b/tests/optimizer.rs
index ac2d5f7f..8f64d7a2 100644
--- a/tests/optimizer.rs
+++ b/tests/optimizer.rs
@@ -86,7 +86,7 @@ fn test_optimizer_parse() -> Result<(), Box<EvalAltResult>> {
 
     assert_eq!(
         format!("{:?}", ast),
-        r#"AST { source: None, body: Block[Const(false @ 1:18, "DECISION" @ 1:7, false, 1:1), Expr(123 @ 1:51)], functions: Module, resolver: None }"#
+        r#"AST { source: None, body: Block[Var(false @ 1:18, "DECISION" @ 1:7, Const, false, 1:1), Expr(123 @ 1:51)], functions: Module, resolver: None }"#
     );
 
     let ast = engine.compile("if 1 == 2 { 42 }")?;