Merge pull request #116 from schungx/master

Efficiency improvements and code refactor.

Cargo.toml

@@ -42,21 +42,21 @@ codegen-units = 1
 #panic = 'abort'     # remove stack backtrace for no-std
 
 [dependencies.libm]
-version = "0.2.1"
+version = "*"
 optional = true
 
 [dependencies.core-error]
-version = "0.0.1-rc4"
+version = "*"
 features = ["alloc"]
 optional = true
 
 [dependencies.hashbrown]
-version = "0.7.1"
+version = "*"
 default-features = false
 features = ["ahash", "nightly", "inline-more"]
 optional = true
 
 [dependencies.ahash]
-version = "0.3.2"
+version = "*"
 default-features = false
 optional = true

README.md

@@ -36,14 +36,20 @@ Install the Rhai crate by adding this line to `dependencies`:
 rhai = "0.11.0"
 ```
 
-or simply:
+Use the latest released crate version on [`crates.io`](https::/crates.io/crates/rhai/):
 
 ```toml
 [dependencies]
 rhai = "*"
 ```
 
-to use the latest version.
+Crate versions are released on [`crates.io`](https::/crates.io/crates/rhai/) infrequently, so if you want to track the
+latest features, enhancements and bug fixes, pull directly from GitHub:
+
+```toml
+[dependencies]
+rhai = { git = "https://github.com/jonathandturner/rhai" }
+```
 
 Beware that in order to use pre-releases (e.g. alpha and beta), the exact version must be specified in the `Cargo.toml`.
 
@@ -80,7 +86,7 @@ Related
 
 Other cool projects to check out:
 
-* [ChaiScript](http://chaiscript.com/) - A strong inspiration for Rhai.  An embedded scripting language for C++ that I helped created many moons ago, now being lead by my cousin.
+* [ChaiScript](http://chaiscript.com/) - A strong inspiration for Rhai.  An embedded scripting language for C++ that I helped created many moons ago, now being led by my cousin.
 * Check out the list of [scripting languages for Rust](https://github.com/rust-unofficial/awesome-rust#scripting) on [awesome-rust](https://github.com/rust-unofficial/awesome-rust)
 
 Examples
@@ -252,7 +258,7 @@ let result = engine.eval_expression_with_scope::<i64>(&mut scope, "if x { 42 } e
 Values and types
 ----------------
 
-[`type_of`]: #values-and-types
+[`type_of()`]: #values-and-types
 
 The following primitive types are supported natively:
 
@@ -547,8 +553,8 @@ let result = engine.eval::<i64>("let x = new_ts(); x.foo()")?;
 println!("result: {}", result);                     // prints 1
 ```
 
-[`type_of`] works fine with custom types and returns the name of the type. If `register_type_with_name` is used to register the custom type
+[`type_of()`] works fine with custom types and returns the name of the type. If `register_type_with_name` is used to register the custom type
-with a special "pretty-print" name, [`type_of`] will return that name instead.
+with a special "pretty-print" name, [`type_of()`] will return that name instead.
 
 ```rust
 engine.register_type::<TestStruct>();
@@ -645,6 +651,18 @@ fn main() -> Result<(), EvalAltResult>
 }
 ```
 
+Engine configuration options
+---------------------------
+
+| Method                   | Description                                                                              |
+| ------------------------ | ---------------------------------------------------------------------------------------- |
+| `set_optimization_level` | Set the amount of script _optimizations_ performed. See [`script optimization`].         |
+| `set_max_call_levels`    | Set the maximum number of function call levels (default 50) to avoid infinite recursion. |
+
+[`script optimization`]: #script-optimization
+
+-------
+
 Rhai Language Guide
 ===================
 
@@ -832,9 +850,11 @@ String and char literals follow C-style formatting, with support for Unicode ('`
 
 Hex sequences map to ASCII characters, while '`\u`' maps to 16-bit common Unicode code points and '`\U`' maps the full, 32-bit extended Unicode code points.
 
-Although internally Rhai strings are stored as UTF-8 just like in Rust (they _are_ Rust `String`s),
+Internally Rhai strings are stored as UTF-8 just like Rust (they _are_ Rust `String`s!), but there are major differences.
-in the Rhai language they can be considered a stream of Unicode characters, and can be directly indexed (unlike Rust).
+In Rhai a string is the same as an array of Unicode characters and can be directly indexed (unlike Rust).
-Individual characters within a Rhai string can be replaced. In Rhai, there is no separate concepts of `String` and `&str` as in Rust.
+This is similar to most other languages where strings are internally represented not as UTF-8 but as arrays of multi-byte Unicode characters.
+Individual characters within a Rhai string can also be replaced just as if the string is an array of Unicode characters.
+In Rhai, there is also no separate concepts of `String` and `&str` as in Rust.
 
 Strings can be built up from other strings and types via the `+` operator (provided by the standard library but excluded if [`no_stdlib`]).
 This is particularly useful when printing output.
@@ -926,9 +946,11 @@ Arrays
 ------
 
 Arrays are first-class citizens in Rhai. Like C, arrays are accessed with zero-based, non-negative integer indices.
-Array literals are built within square brackets '`[`' ,, '`]`' and separated by commas '`,`'.
+Array literals are built within square brackets '`[`' ... '`]`' and separated by commas '`,`'.
 
-The type of a Rhai array is `rhai::Array`. [`type_of()`] an array returns `"array"`.
+The Rust type of a Rhai array is `rhai::Array`.
+
+[`type_of()`] an array returns `"array"`.
 
 Arrays are disabled via the [`no_index`] feature.
 
@@ -1075,17 +1097,13 @@ my_str += 12345;
 my_str == "abcABC12345"
 ```
 
-If statements
+`if` statements
--------------
+---------------
-
-All branches of an `if` statement must be enclosed within braces '`{`' .. '`}`', even when there is only one statement.
-
-Like Rust, there is no ambiguity regarding which `if` clause a statement belongs to.
 
 ```rust
-if true {
+if foo(x) {
     print("It's true!");
-} else if true {
+} else if bar == baz {
     print("It's true again!");
 } else if ... {
         :
@@ -1094,13 +1112,28 @@ if true {
 } else {
     print("It's finally false!");
 }
+```
 
+All branches of an `if` statement must be enclosed within braces '`{`' .. '`}`', even when there is only one statement.
+Like Rust, there is no ambiguity regarding which `if` clause a statement belongs to.
+
+```rust
 if (decision) print("I've decided!");
 //            ^ syntax error, expecting '{' in statement block
 ```
 
-While loops
+Like Rust, `if` statements can also be used as _expressions_, replacing the `? :` conditional operators in other C-like languages.
------------
+
+```rust
+let x = 1 + if true { 42 } else { 123 } / 2;
+x == 22;
+
+let x = if false { 42 };    // No else branch defaults to '()'
+x == ();
+```
+
+`while` loops
+-------------
 
 ```rust
 let x = 10;
@@ -1112,8 +1145,8 @@ while x > 0 {
 }
 ```
 
-Infinite loops
+Infinite `loop`
---------------
+---------------
 
 ```rust
 let x = 10;
@@ -1125,8 +1158,8 @@ loop {
 }
 ```
 
-For loops
+`for` loops
----------
+-----------
 
 Iterating through a range or an array is provided by the `for` ... `in` loop.
 
@@ -1146,8 +1179,8 @@ for x in range(0, 50) {
 }
 ```
 
-Returning values
+`return`-ing values
-----------------
+-------------------
 
 ```rust
 return;             // equivalent to return ();
@@ -1155,8 +1188,8 @@ return;             // equivalent to return ();
 return 123 + 456;   // returns 579
 ```
 
-Errors and exceptions
+Errors and `throw`-ing exceptions
----------------------
+--------------------------------
 
 All of [`Engine`]'s evaluation/consuming methods return `Result<T, rhai::EvalAltResult>` with `EvalAltResult` holding error information.
 To deliberately return an error during an evaluation, use the `throw` keyword.
@@ -1197,8 +1230,10 @@ fn add(x, y) {
 print(add(2, 3));
 ```
 
+### Implicit return
+
 Just like in Rust, an implicit return can be used. In fact, the last statement of a block is _always_ the block's return value
-regardless of whether it is terminated with a semicolon `;`. This is different from Rust.
+regardless of whether it is terminated with a semicolon `';'`. This is different from Rust.
 
 ```rust
 fn add(x, y) {
@@ -1213,6 +1248,16 @@ print(add(2, 3));   // prints 5
 print(add2(42));    // prints 44
 ```
 
+### No access to external scope
+
+Functions can only access their parameters.  They cannot access external variables (even _global_ variables).
+
+```rust
+let x = 42;
+
+fn foo() { x }      // syntax error - variable 'x' doesn't exist
+```
+
 ### Passing arguments by value
 
 Functions defined in script always take [`Dynamic`] parameters (i.e. the parameter can be of any type).
@@ -1225,7 +1270,7 @@ fn change(s) {  // 's' is passed by value
 }
 
 let x = 500;
-x.change();     // desugars to change(x)
+x.change();     // de-sugars to change(x)
 x == 500;       // 'x' is NOT changed!
 ```
 
@@ -1251,31 +1296,34 @@ fn do_addition(x) {
 
 ### Functions overloading
 
-Functions can be _overloaded_ based on the _number_ of parameters (but not parameter _types_, since all parameters are the same type - [`Dynamic`]).
+Functions can be _overloaded_ and are resolved purely upon the function's _name_ and the _number_ of parameters
-New definitions of the same name and number of parameters overwrite previous definitions.
+(but not parameter _types_, since all parameters are the same type - [`Dynamic`]).
+New definitions _overwrite_ previous definitions of the same name and number of parameters.
 
 ```rust
-fn abc(x,y,z) { print("Three!!! " + x + "," + y + "," + z) }
+fn foo(x,y,z) { print("Three!!! " + x + "," + y + "," + z) }
-fn abc(x) { print("One! " + x) }
+fn foo(x) { print("One! " + x) }
-fn abc(x,y) { print("Two! " + x + "," + y) }
+fn foo(x,y) { print("Two! " + x + "," + y) }
-fn abc() { print("None.") }
+fn foo() { print("None.") }
-fn abc(x) { print("HA! NEW ONE! " + x) }    // overwrites previous definition
+fn foo(x) { print("HA! NEW ONE! " + x) }    // overwrites previous definition
 
-abc(1,2,3);     // prints "Three!!! 1,2,3"
+foo(1,2,3);     // prints "Three!!! 1,2,3"
-abc(42);        // prints "HA! NEW ONE! 42"
+foo(42);        // prints "HA! NEW ONE! 42"
-abc(1,2);       // prints "Two!! 1,2"
+foo(1,2);       // prints "Two!! 1,2"
-abc();          // prints "None."
+foo();          // prints "None."
 ```
 
 Members and methods
 -------------------
 
-Properties and methods in a Rust custom type registered with the [`Engine`] can be called just like in Rust:
+Properties and methods in a Rust custom type registered with the [`Engine`] can be called just like in Rust.
 
 ```rust
 let a = new_ts();       // constructor function
 a.field = 500;          // property access
 a.update();             // method call
+
+update(a);              // this works, but 'a' is unchanged because only a COPY of 'a' is passed to 'update' by VALUE
 ```
 
 `print` and `debug`

examples/arrays_and_structs.rs

@@ -1,8 +1,8 @@
-use rhai::{Engine, RegisterFn};
+use rhai::{Engine, RegisterFn, INT};
 
 #[derive(Clone, Debug)]
 struct TestStruct {
-    x: i64,
+    x: INT,
 }
 
 impl TestStruct {

examples/custom_types_and_methods.rs

@@ -1,8 +1,8 @@
-use rhai::{Engine, EvalAltResult, RegisterFn};
+use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
 #[derive(Clone)]
 struct TestStruct {
-    x: i64,
+    x: INT,
 }
 
 impl TestStruct {

examples/hello.rs

@@ -1,9 +1,9 @@
-use rhai::{Engine, EvalAltResult};
+use rhai::{Engine, EvalAltResult, INT};
 
 fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
-    let result = engine.eval::<i64>("40 + 2")?;
+    let result = engine.eval::<INT>("40 + 2")?;
 
     println!("Answer: {}", result); // prints 42
 

examples/no_std.rs

@@ -1,12 +1,16 @@
 #![cfg_attr(feature = "no_std", no_std)]
 
-use rhai::{Engine, EvalAltResult};
+use rhai::{Engine, EvalAltResult, INT};
 
 fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
-    let result = engine.eval::<i64>("40 + 2")?;
+    let result = engine.eval::<INT>("40 + 2")?;
 
+    #[cfg(not(feature = "no_std"))]
+    println!("Answer: {}", result);
+
+    #[cfg(feature = "no_std")]
     assert_eq!(result, 42);
 
     Ok(())

examples/repl.rs

@@ -1,4 +1,4 @@
-use rhai::{Engine, EvalAltResult, Scope, AST};
+use rhai::{Engine, EvalAltResult, Position, Scope, AST};
 
 #[cfg(not(feature = "no_optimize"))]
 use rhai::OptimizationLevel;
@@ -13,7 +13,7 @@ fn print_error(input: &str, err: EvalAltResult) {
         iter::repeat(pad).take(len).collect::<String>()
     }
 
-    let lines: Vec<_> = input.trim().split("\n").collect();
+    let lines: Vec<_> = input.trim().split('\n').collect();
 
     let line_no = if lines.len() > 1 {
         match err.position() {
@@ -26,27 +26,18 @@ fn print_error(input: &str, err: EvalAltResult) {
     };
 
     // Print error
-    let pos_text = format!(" ({})", err.position());
+    let pos = err.position();
+    let pos_text = format!(" ({})", pos);
 
-    match err.position() {
+    let pos = if pos.is_eof() {
-        p if p.is_eof() => {
-            // EOF
         let last = lines[lines.len() - 1];
-            println!("{}{}", line_no, last);
+        Position::new(lines.len(), last.len() + 1)
-
+    } else {
-            let err_text = match err {
+        pos
-                EvalAltResult::ErrorRuntime(err, _) if !err.is_empty() => {
-                    format!("Runtime error: {}", err)
-                }
-                _ => err.to_string(),
     };
 
-            println!(
+    match pos {
-                "{}^ {}",
+        p if p.is_eof() => panic!("should not be EOF"),
-                padding(" ", line_no.len() + last.len() - 1),
-                err_text.replace(&pos_text, "")
-            );
-        }
         p if p.is_none() => {
             // No position
             println!("{}", err);
@@ -59,7 +50,7 @@ fn print_error(input: &str, err: EvalAltResult) {
                 EvalAltResult::ErrorRuntime(err, _) if !err.is_empty() => {
                     format!("Runtime error: {}", err)
                 }
-                _ => err.to_string(),
+                err => err.to_string(),
             };
 
             println!(
@@ -161,7 +152,7 @@ fn main() {
                 #[cfg(not(feature = "no_optimize"))]
                 {
                     engine.set_optimization_level(OptimizationLevel::Full);
-                    ast = Some(engine.optimize_ast(&mut scope, ast_u.as_ref().unwrap()));
+                    ast = Some(engine.optimize_ast(&scope, ast_u.as_ref().unwrap()));
                     engine.set_optimization_level(OptimizationLevel::None);
                 }
 
@@ -178,9 +169,9 @@ fn main() {
                     })
             })
         {
-            println!("");
+            println!();
             print_error(&input, err);
-            println!("");
+            println!();
         }
     }
 }

examples/reuse_scope.rs

@@ -1,4 +1,4 @@
-use rhai::{Engine, EvalAltResult, Scope};
+use rhai::{Engine, EvalAltResult, Scope, INT};
 
 fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
@@ -6,7 +6,7 @@ fn main() -> Result<(), EvalAltResult> {
 
     engine.eval_with_scope::<()>(&mut scope, "let x = 4 + 5")?;
 
-    let result = engine.eval_with_scope::<i64>(&mut scope, "x")?;
+    let result = engine.eval_with_scope::<INT>(&mut scope, "x")?;
 
     println!("result: {}", result);
 

examples/rhai_runner.rs

@@ -1,4 +1,4 @@
-use rhai::{Engine, EvalAltResult};
+use rhai::{Engine, EvalAltResult, Position};
 
 #[cfg(not(feature = "no_optimize"))]
 use rhai::OptimizationLevel;
@@ -10,7 +10,7 @@ fn padding(pad: &str, len: usize) -> String {
 }
 
 fn eprint_error(input: &str, err: EvalAltResult) {
-    fn eprint_line(lines: &Vec<&str>, line: usize, pos: usize, err: &str) {
+    fn eprint_line(lines: &[&str], line: usize, pos: usize, err: &str) {
         let line_no = format!("{}: ", line);
         let pos_text = format!(" (line {}, position {})", line, pos);
 
@@ -23,34 +23,32 @@ fn eprint_error(input: &str, err: EvalAltResult) {
         eprintln!("");
     }
 
-    let lines: Vec<_> = input.split("\n").collect();
+    let lines: Vec<_> = input.split('\n').collect();
 
     // Print error
-    match err.position() {
+    let pos = if err.position().is_eof() {
-        p if p.is_eof() => {
+        let last = lines[lines.len() - 1];
-            // EOF
+        Position::new(lines.len(), last.len() + 1)
-            let line = lines.len() - 1;
+    } else {
-            let pos = lines[line - 1].len();
+        err.position()
-            let err_text = match err {
-                EvalAltResult::ErrorRuntime(err, _) if !err.is_empty() => {
-                    format!("Runtime error: {}", err)
-                }
-                _ => err.to_string(),
     };
-            eprint_line(&lines, line, pos, &err_text);
+
-        }
+    match pos {
+        p if p.is_eof() => panic!("should not be EOF"),
         p if p.is_none() => {
             // No position
             eprintln!("{}", err);
         }
         p => {
             // Specific position
-            eprint_line(
+            let err_text = match err {
-                &lines,
+                EvalAltResult::ErrorRuntime(err, _) if !err.is_empty() => {
-                p.line().unwrap(),
+                    format!("Runtime error: {}", err)
-                p.position().unwrap(),
+                }
-                &err.to_string(),
+                err => err.to_string(),
-            )
+            };
+
+            eprint_line(&lines, p.line().unwrap(), p.position().unwrap(), &err_text)
         }
     }
 }
@@ -72,13 +70,10 @@ fn main() {
 
         let mut contents = String::new();
 
-        match f.read_to_string(&mut contents) {
+        if let Err(err) = f.read_to_string(&mut contents) {
-            Err(err) => {
             eprintln!("Error reading script file: {}\n{}", filename, err);
             exit(1);
         }
-            _ => (),
-        }
 
         if let Err(err) = engine.consume(false, &contents) {
             eprintln!("{}", padding("=", filename.len()));

examples/simple_fn.rs

@@ -1,15 +1,15 @@
-use rhai::{Engine, EvalAltResult, RegisterFn};
+use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
 fn main() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
 
-    fn add(x: i64, y: i64) -> i64 {
+    fn add(x: INT, y: INT) -> INT {
         x + y
     }
 
     engine.register_fn("add", add);
 
-    let result = engine.eval::<i64>("add(40, 2)")?;
+    let result = engine.eval::<INT>("add(40, 2)")?;
 
     println!("Answer: {}", result); // prints 42
 

src/api.rs

@@ -15,6 +15,7 @@ use crate::optimize::optimize_into_ast;
 use crate::stdlib::{
     any::{type_name, TypeId},
     boxed::Box,
+    format,
     string::{String, ToString},
     sync::Arc,
     vec::Vec,
@@ -35,7 +36,7 @@ impl<'e> Engine<'e> {
             args,
         };
 
-        self.ext_functions.insert(spec, f);
+        self.functions.insert(spec, f);
     }
 
     /// Register a custom type for use with the `Engine`.
@@ -725,11 +726,9 @@ impl<'e> Engine<'e> {
                 statements
             };
 
-            let mut result = ().into_dynamic();
+            let result = statements.iter().try_fold(().into_dynamic(), |_, stmt| {
-
+                engine.eval_stmt(scope, stmt, 0)
-            for stmt in statements {
+            })?;
-                result = engine.eval_stmt(scope, stmt)?;
-            }
 
             if !retain_functions {
                 engine.clear_functions();
@@ -828,7 +827,7 @@ impl<'e> Engine<'e> {
 
         let result = statements
             .iter()
-            .try_fold(().into_dynamic(), |_, o| self.eval_stmt(scope, o))
+            .try_fold(().into_dynamic(), |_, stmt| self.eval_stmt(scope, stmt, 0))
             .map(|_| ());
 
         if !retain_functions {
@@ -847,13 +846,7 @@ impl<'e> Engine<'e> {
         functions: impl IntoIterator<Item = &'a Arc<FnDef>>,
     ) {
         for f in functions.into_iter() {
-            match self
+            self.fn_lib.add_or_replace_function(f.clone());
-                .script_functions
-                .binary_search_by(|fn_def| fn_def.compare(&f.name, f.params.len()))
-            {
-                Ok(n) => self.script_functions[n] = f.clone(),
-                Err(n) => self.script_functions.insert(n, f.clone()),
-            }
         }
     }
 
@@ -887,20 +880,11 @@ impl<'e> Engine<'e> {
         name: &str,
         args: A,
     ) -> Result<T, EvalAltResult> {
-        // Split out non-generic portion to avoid exploding code size
+        let mut values = args.into_vec();
-        fn call_fn_internal(
+        let mut arg_values: Vec<_> = values.iter_mut().map(Dynamic::as_mut).collect();
-            engine: &mut Engine,
-            name: &str,
-            mut values: Vec<Dynamic>,
-        ) -> Result<Dynamic, EvalAltResult> {
-            let values: Vec<_> = values.iter_mut().map(Dynamic::as_mut).collect();
 
-            let result = engine.call_fn_raw(name, values, None, Position::none());
+        self.call_fn_raw(name, &mut arg_values, None, Position::none(), 0)
-
+            .and_then(|b| {
-            result
-        }
-
-        call_fn_internal(self, name, args.into_vec()).and_then(|b| {
                 b.downcast().map(|b| *b).map_err(|a| {
                     EvalAltResult::ErrorMismatchOutputType(
                         self.map_type_name((*a).type_name()).into(),

src/builtin.rs

@@ -57,7 +57,7 @@ macro_rules! reg_op_result1 {
 impl Engine<'_> {
     /// Register the core built-in library.
     pub(crate) fn register_core_lib(&mut self) {
-        /// Checked add
+        // Checked add
         #[cfg(not(feature = "unchecked"))]
         fn add<T: Display + CheckedAdd>(x: T, y: T) -> Result<T, EvalAltResult> {
             x.checked_add(&y).ok_or_else(|| {
@@ -67,7 +67,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked subtract
+        // Checked subtract
         #[cfg(not(feature = "unchecked"))]
         fn sub<T: Display + CheckedSub>(x: T, y: T) -> Result<T, EvalAltResult> {
             x.checked_sub(&y).ok_or_else(|| {
@@ -77,7 +77,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked multiply
+        // Checked multiply
         #[cfg(not(feature = "unchecked"))]
         fn mul<T: Display + CheckedMul>(x: T, y: T) -> Result<T, EvalAltResult> {
             x.checked_mul(&y).ok_or_else(|| {
@@ -87,7 +87,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked divide
+        // Checked divide
         #[cfg(not(feature = "unchecked"))]
         fn div<T>(x: T, y: T) -> Result<T, EvalAltResult>
         where
@@ -108,7 +108,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked negative - e.g. -(i32::MIN) will overflow i32::MAX
+        // Checked negative - e.g. -(i32::MIN) will overflow i32::MAX
         #[cfg(not(feature = "unchecked"))]
         fn neg<T: Display + CheckedNeg>(x: T) -> Result<T, EvalAltResult> {
             x.checked_neg().ok_or_else(|| {
@@ -118,7 +118,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked absolute
+        // Checked absolute
         #[cfg(not(feature = "unchecked"))]
         fn abs<T: Display + CheckedNeg + PartialOrd + Zero>(x: T) -> Result<T, EvalAltResult> {
             // FIX - We don't use Signed::abs() here because, contrary to documentation, it panics
@@ -134,32 +134,32 @@ impl Engine<'_> {
                 })
             }
         }
-        /// Unchecked add - may panic on overflow
+        // Unchecked add - may panic on overflow
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn add_u<T: Add>(x: T, y: T) -> <T as Add>::Output {
             x + y
         }
-        /// Unchecked subtract - may panic on underflow
+        // Unchecked subtract - may panic on underflow
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn sub_u<T: Sub>(x: T, y: T) -> <T as Sub>::Output {
             x - y
         }
-        /// Unchecked multiply - may panic on overflow
+        // Unchecked multiply - may panic on overflow
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn mul_u<T: Mul>(x: T, y: T) -> <T as Mul>::Output {
             x * y
         }
-        /// Unchecked divide - may panic when dividing by zero
+        // Unchecked divide - may panic when dividing by zero
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn div_u<T: Div>(x: T, y: T) -> <T as Div>::Output {
             x / y
         }
-        /// Unchecked negative - may panic on overflow
+        // Unchecked negative - may panic on overflow
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn neg_u<T: Neg>(x: T) -> <T as Neg>::Output {
             -x
         }
-        /// Unchecked absolute - may panic on overflow
+        // Unchecked absolute - may panic on overflow
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn abs_u<T>(x: T) -> <T as Neg>::Output
         where
@@ -174,7 +174,6 @@ impl Engine<'_> {
         }
 
         // Comparison operators
-
         fn lt<T: PartialOrd>(x: T, y: T) -> bool {
             x < y
         }
@@ -195,7 +194,6 @@ impl Engine<'_> {
         }
 
         // Logic operators
-
         fn and(x: bool, y: bool) -> bool {
             x && y
         }
@@ -207,7 +205,6 @@ impl Engine<'_> {
         }
 
         // Bit operators
-
         fn binary_and<T: BitAnd>(x: T, y: T) -> <T as BitAnd>::Output {
             x & y
         }
@@ -218,7 +215,7 @@ impl Engine<'_> {
             x ^ y
         }
 
-        /// Checked left-shift
+        // Checked left-shift
         #[cfg(not(feature = "unchecked"))]
         fn shl<T: Display + CheckedShl>(x: T, y: INT) -> Result<T, EvalAltResult> {
             // Cannot shift by a negative number of bits
@@ -236,7 +233,7 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Checked right-shift
+        // Checked right-shift
         #[cfg(not(feature = "unchecked"))]
         fn shr<T: Display + CheckedShr>(x: T, y: INT) -> Result<T, EvalAltResult> {
             // Cannot shift by a negative number of bits
@@ -254,17 +251,17 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Unchecked left-shift - may panic if shifting by a negative number of bits
+        // Unchecked left-shift - may panic if shifting by a negative number of bits
         #[cfg(feature = "unchecked")]
         fn shl_u<T: Shl<T>>(x: T, y: T) -> <T as Shl<T>>::Output {
             x.shl(y)
         }
-        /// Unchecked right-shift - may panic if shifting by a negative number of bits
+        // Unchecked right-shift - may panic if shifting by a negative number of bits
         #[cfg(feature = "unchecked")]
         fn shr_u<T: Shr<T>>(x: T, y: T) -> <T as Shr<T>>::Output {
             x.shr(y)
         }
-        /// Checked modulo
+        // Checked modulo
         #[cfg(not(feature = "unchecked"))]
         fn modulo<T: Display + CheckedRem>(x: T, y: T) -> Result<T, EvalAltResult> {
             x.checked_rem(&y).ok_or_else(|| {
@@ -274,12 +271,12 @@ impl Engine<'_> {
                 )
             })
         }
-        /// Unchecked modulo - may panic if dividing by zero
+        // Unchecked modulo - may panic if dividing by zero
         #[cfg(any(feature = "unchecked", not(feature = "no_float")))]
         fn modulo_u<T: Rem>(x: T, y: T) -> <T as Rem>::Output {
             x % y
         }
-        /// Checked power
+        // Checked power
         #[cfg(not(feature = "unchecked"))]
         fn pow_i_i(x: INT, y: INT) -> Result<INT, EvalAltResult> {
             #[cfg(not(feature = "only_i32"))]
@@ -321,17 +318,17 @@ impl Engine<'_> {
                 }
             }
         }
-        /// Unchecked integer power - may panic on overflow or if the power index is too high (> u32::MAX)
+        // Unchecked integer power - may panic on overflow or if the power index is too high (> u32::MAX)
         #[cfg(feature = "unchecked")]
         fn pow_i_i_u(x: INT, y: INT) -> INT {
             x.pow(y as u32)
         }
-        /// Floating-point power - always well-defined
+        // Floating-point power - always well-defined
         #[cfg(not(feature = "no_float"))]
         fn pow_f_f(x: FLOAT, y: FLOAT) -> FLOAT {
             x.powf(y)
         }
-        /// Checked power
+        // Checked power
         #[cfg(not(feature = "unchecked"))]
         #[cfg(not(feature = "no_float"))]
         fn pow_f_i(x: FLOAT, y: INT) -> Result<FLOAT, EvalAltResult> {
@@ -345,7 +342,7 @@ impl Engine<'_> {
 
             Ok(x.powi(y as i32))
         }
-        /// Unchecked power - may be incorrect if the power index is too high (> i32::MAX)
+        // Unchecked power - may be incorrect if the power index is too high (> i32::MAX)
         #[cfg(feature = "unchecked")]
         #[cfg(not(feature = "no_float"))]
         fn pow_f_i_u(x: FLOAT, y: INT) -> FLOAT {
@@ -432,7 +429,8 @@ impl Engine<'_> {
             }
         }
 
-        // `&&` and `||` are treated specially as they short-circuit
+        // `&&` and `||` are treated specially as they short-circuit.
+        // They are implemented as special `Expr` instances, not function calls.
         //reg_op!(self, "||", or, bool);
         //reg_op!(self, "&&", and, bool);
 
@@ -623,10 +621,6 @@ impl Engine<'_> {
             });
         }
 
-        fn range<T>(from: T, to: T) -> Range<T> {
-            from..to
-        }
-
         reg_iterator::<INT>(self);
         self.register_fn("range", |i1: INT, i2: INT| (i1..i2));
 
@@ -634,15 +628,15 @@ impl Engine<'_> {
         #[cfg(not(feature = "only_i64"))]
         {
             macro_rules! reg_range {
-                ($self:expr, $x:expr, $op:expr, $( $y:ty ),*) => (
+                ($self:expr, $x:expr, $( $y:ty ),*) => (
                     $(
                         reg_iterator::<$y>(self);
-                        $self.register_fn($x, $op as fn(x: $y, y: $y)->Range<$y>);
+                        $self.register_fn($x, (|x: $y, y: $y| x..y) as fn(x: $y, y: $y)->Range<$y>);
                     )*
                 )
             }
 
-            reg_range!(self, "range", range, i8, u8, i16, u16, i32, i64, u32, u64);
+            reg_range!(self, "range", i8, u8, i16, u16, i32, i64, u32, u64);
         }
     }
 }
@@ -837,10 +831,10 @@ impl Engine<'_> {
         }
 
         reg_fn2x!(self, "+", append, String, String, INT, bool, char);
-        self.register_fn("+", |x: String, _: ()| format!("{}", x));
+        self.register_fn("+", |x: String, _: ()| x);
 
         reg_fn2y!(self, "+", prepend, String, String, INT, bool, char);
-        self.register_fn("+", |_: (), y: String| format!("{}", y));
+        self.register_fn("+", |_: (), y: String| y);
 
         #[cfg(not(feature = "only_i32"))]
         #[cfg(not(feature = "only_i64"))]
@@ -891,9 +885,7 @@ impl Engine<'_> {
             let trimmed = s.trim();
 
             if trimmed.len() < s.len() {
-                let chars: Vec<_> = trimmed.chars().collect();
+                *s = trimmed.to_string();
-                s.clear();
-                chars.iter().for_each(|&ch| s.push(ch));
             }
         });
     }

src/call.rs

@@ -11,11 +11,15 @@ use crate::engine::Array;
 use crate::stdlib::{string::String, vec, vec::Vec};
 
 /// Trait that represent arguments to a function call.
+/// Any data type that can be converted into a `Vec` of `Dynamic` values can be used
+/// as arguments to a function call.
 pub trait FuncArgs {
     /// Convert to a `Vec` of `Dynamic` arguments.
     fn into_vec(self) -> Vec<Dynamic>;
 }
 
+/// Macro to implement `FuncArgs` for a single standard type that can be converted
+/// into `Dynamic`.
 macro_rules! impl_std_args {
     ($($p:ty),*) => {
         $(
@@ -43,6 +47,8 @@ impl_std_args!(INT);
 #[cfg(not(feature = "no_float"))]
 impl_std_args!(f32, f64);
 
+/// Macro to implement `FuncArgs` for tuples of standard types (each can be
+/// converted into `Dynamic`).
 macro_rules! impl_args {
     ($($p:ident),*) => {
         impl<$($p: Any + Clone),*> FuncArgs for ($($p,)*)
@@ -69,5 +75,5 @@ macro_rules! impl_args {
     };
 }
 
-#[cfg_attr(rustfmt, rustfmt_skip)]
+#[rustfmt::skip]
-impl_args!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T);
+impl_args!(A, B, C, D, E, F, G, H, J, K, L, M, N, P, Q, R, S, T, U, V);

src/error.rs

@@ -17,8 +17,6 @@ pub enum LexError {
     MalformedNumber(String),
     /// An character literal is in an invalid format.
     MalformedChar(String),
-    /// Error in the script text.
-    InputError(String),
     /// An identifier is in an invalid format.
     MalformedIdentifier(String),
 }
@@ -35,7 +33,6 @@ impl fmt::Display for LexError {
             Self::MalformedIdentifier(s) => {
                 write!(f, "Variable name is not in a legal format: '{}'", s)
             }
-            Self::InputError(s) => write!(f, "{}", s),
             Self::UnterminatedString => write!(f, "Open string is not terminated"),
         }
     }
@@ -85,6 +82,9 @@ pub enum ParseErrorType {
     /// A function definition is missing the parameters list. Wrapped value is the function name.
     #[cfg(not(feature = "no_function"))]
     FnMissingParams(String),
+    /// A function definition has duplicated parameters. Wrapped values are the function name and parameter name.
+    #[cfg(not(feature = "no_function"))]
+    FnDuplicateParam(String, String),
     /// A function definition is missing the body. Wrapped value is the function name.
     #[cfg(not(feature = "no_function"))]
     FnMissingBody(String),
@@ -98,16 +98,23 @@ pub enum ParseErrorType {
     LoopBreak,
 }
 
+impl ParseErrorType {
+    /// Make a `ParseError` using the current type and position.
+    pub(crate) fn into_err(self, pos: Position) -> ParseError {
+        ParseError(self, pos)
+    }
+
+    /// Make a `ParseError` using the current type and EOF position.
+    pub(crate) fn into_err_eof(self) -> ParseError {
+        ParseError(self, Position::eof())
+    }
+}
+
 /// Error when parsing a script.
 #[derive(Debug, PartialEq, Clone)]
 pub struct ParseError(pub(crate) ParseErrorType, pub(crate) Position);
 
 impl ParseError {
-    /// Create a new `ParseError`.
-    pub(crate) fn new(err: ParseErrorType, pos: Position) -> Self {
-        Self(err, pos)
-    }
-
     /// Get the parse error.
     pub fn error_type(&self) -> &ParseErrorType {
         &self.0
@@ -142,6 +149,8 @@ impl ParseError {
             #[cfg(not(feature = "no_function"))]
             ParseErrorType::FnMissingParams(_) => "Expecting parameters in function declaration",
             #[cfg(not(feature = "no_function"))]
+            ParseErrorType::FnDuplicateParam(_,_) => "Duplicated parameters in function declaration",
+            #[cfg(not(feature = "no_function"))]
             ParseErrorType::FnMissingBody(_) => "Expecting body statement block for function declaration",
             #[cfg(not(feature = "no_function"))]
             ParseErrorType::WrongFnDefinition => "Function definitions must be at global level and cannot be inside a block or another function",
@@ -183,6 +192,11 @@ impl fmt::Display for ParseError {
                 write!(f, "Expecting body statement block for function '{}'", s)?
             }
 
+            #[cfg(not(feature = "no_function"))]
+            ParseErrorType::FnDuplicateParam(ref s, ref arg) => {
+                write!(f, "Duplicated parameter '{}' for function '{}'", arg, s)?
+            }
+
             ParseErrorType::MissingRightParen(ref s) | ParseErrorType::MissingRightBrace(ref s) => {
                 write!(f, "{} for {}", self.desc(), s)?
             }

src/fn_register.rs

@@ -80,7 +80,8 @@ pub trait RegisterResultFn<FN, ARGS, RET> {
     /// // Normal function
     /// fn div(x: i64, y: i64) -> Result<i64, EvalAltResult> {
     ///     if y == 0 {
-    ///         Err("division by zero!".into())     // '.into()' automatically converts to 'EvalAltResult::ErrorRuntime'
+    ///         // '.into()' automatically converts to 'EvalAltResult::ErrorRuntime'
+    ///         Err("division by zero!".into())
     ///     } else {
     ///         Ok(x / y)
     ///     }
@@ -97,9 +98,30 @@ pub trait RegisterResultFn<FN, ARGS, RET> {
     fn register_result_fn(&mut self, name: &str, f: FN);
 }
 
-pub struct Ref<A>(A);
+// These types are used to build a unique _marker_ tuple type for each combination
-pub struct Mut<A>(A);
+// of function parameter types in order to make each trait implementation unique.
+// That is because stable Rust currently does not allow distinguishing implementations
+// based purely on parameter types of traits (Fn, FnOnce and FnMut).
+//
+// For example:
+//
+// `RegisterFn<FN, (Mut<A>, B, Ref<C>), R>`
+//
+// will have the function prototype constraint to:
+//
+// `FN: (&mut A, B, &C) -> R`
+//
+// These types are not actually used anywhere.
+pub struct Mut<T>(T);
+//pub struct Ref<T>(T);
 
+/// Identity dereferencing function.
+#[inline]
+fn identity<T>(data: T) -> T {
+    data
+}
+
+/// This macro counts the number of arguments via recursion.
 macro_rules! count_args {
     () => { 0_usize };
     ( $head:ident $($tail:ident)* ) => { 1_usize + count_args!($($tail)*) };
@@ -110,6 +132,10 @@ macro_rules! def_register {
         def_register!(imp);
     };
     (imp $($par:ident => $mark:ty => $param:ty => $clone:expr),*) => {
+    //     ^ function parameter generic type name
+    //                   ^ function parameter marker type (T, Ref<T> or Mut<T>)
+    //                               ^ function parameter actual type
+    //                                            ^ dereferencing function
         impl<
             $($par: Any + Clone,)*
             FN: Fn($($param),*) -> RET + 'static,
@@ -119,7 +145,7 @@ macro_rules! def_register {
             fn register_fn(&mut self, name: &str, f: FN) {
                 let fn_name = name.to_string();
 
-                let fun = move |mut args: FnCallArgs, pos: Position| {
+                let fun = move |args: &mut FnCallArgs, pos: Position| {
                     // Check for length at the beginning to avoid per-element bound checks.
                     const NUM_ARGS: usize = count_args!($($par)*);
 
@@ -128,7 +154,7 @@ macro_rules! def_register {
                     }
 
                     #[allow(unused_variables, unused_mut)]
-                    let mut drain = args.drain(..);
+                    let mut drain = args.iter_mut();
                     $(
                     // Downcast every element, return in case of a type mismatch
                     let $par = drain.next().unwrap().downcast_mut::<$par>().unwrap();
@@ -151,7 +177,7 @@ macro_rules! def_register {
             fn register_dynamic_fn(&mut self, name: &str, f: FN) {
                 let fn_name = name.to_string();
 
-                let fun = move |mut args: FnCallArgs, pos: Position| {
+                let fun = move |args: &mut FnCallArgs, pos: Position| {
                     // Check for length at the beginning to avoid per-element bound checks.
                     const NUM_ARGS: usize = count_args!($($par)*);
 
@@ -160,7 +186,7 @@ macro_rules! def_register {
                     }
 
                     #[allow(unused_variables, unused_mut)]
-                    let mut drain = args.drain(..);
+                    let mut drain = args.iter_mut();
                     $(
                     // Downcast every element, return in case of a type mismatch
                     let $par = drain.next().unwrap().downcast_mut::<$par>().unwrap();
@@ -183,7 +209,7 @@ macro_rules! def_register {
             fn register_result_fn(&mut self, name: &str, f: FN) {
                 let fn_name = name.to_string();
 
-                let fun = move |mut args: FnCallArgs, pos: Position| {
+                let fun = move |args: &mut FnCallArgs, pos: Position| {
                     // Check for length at the beginning to avoid per-element bound checks.
                     const NUM_ARGS: usize = count_args!($($par)*);
 
@@ -192,7 +218,7 @@ macro_rules! def_register {
                     }
 
                     #[allow(unused_variables, unused_mut)]
-                    let mut drain = args.drain(..);
+                    let mut drain = args.iter_mut();
                     $(
                     // Downcast every element, return in case of a type mismatch
                     let $par = drain.next().unwrap().downcast_mut::<$par>().unwrap();
@@ -200,10 +226,8 @@ macro_rules! def_register {
 
                     // Call the user-supplied function using ($clone) to
                     // potentially clone the value, otherwise pass the reference.
-                    f($(($clone)($par)),*).map(|r| Box::new(r) as Dynamic).map_err(|mut err| {
+                    f($(($clone)($par)),*).map(|r| Box::new(r) as Dynamic)
-                        err.set_position(pos);
+                                          .map_err(|err| err.set_position(pos))
-                        err
-                    })
                 };
                 self.register_fn_raw(name, Some(vec![$(TypeId::of::<$par>()),*]), Box::new(fun));
             }
@@ -213,8 +237,12 @@ macro_rules! def_register {
     };
     ($p0:ident $(, $p:ident)*) => {
         def_register!(imp $p0 => $p0      => $p0      => Clone::clone   $(, $p => $p => $p => Clone::clone)*);
-        def_register!(imp $p0 => Ref<$p0> => &$p0 => |x| { x } $(, $p => $p => $p => Clone::clone)*);
+        def_register!(imp $p0 => Mut<$p0> => &mut $p0 => identity       $(, $p => $p => $p => Clone::clone)*);
-        def_register!(imp $p0 => Mut<$p0> => &mut $p0 => |x| { x } $(, $p => $p => $p => Clone::clone)*);
+        // handle the first parameter                    ^ first parameter passed through
+        //                                                    others passed by value (cloned) ^
+
+        // No support for functions where the first argument is a reference
+        //def_register!(imp $p0 => Ref<$p0> => &$p0     => identity       $(, $p => $p => $p => Clone::clone)*);
 
         def_register!($($p),*);
     };
@@ -224,5 +252,5 @@ macro_rules! def_register {
 //    };
 }
 
-#[cfg_attr(rustfmt, rustfmt_skip)]
+#[rustfmt::skip]
-def_register!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T);
+def_register!(A, B, C, D, E, F, G, H, J, K, L, M, N, P, Q, R, S, T, U, V);

src/lib.rs

@@ -63,7 +63,7 @@ pub use error::{ParseError, ParseErrorType};
 pub use fn_register::{RegisterDynamicFn, RegisterFn, RegisterResultFn};
 pub use parser::{Position, AST, INT};
 pub use result::EvalAltResult;
-pub use scope::{Scope, ScopeEntry, VariableType};
+pub use scope::Scope;
 
 #[cfg(not(feature = "no_index"))]
 pub use engine::Array;

src/optimize.rs

@@ -2,11 +2,10 @@
 
 use crate::any::{Any, Dynamic};
 use crate::engine::{
-    Engine, FnCallArgs, KEYWORD_DEBUG, KEYWORD_DUMP_AST, KEYWORD_EVAL, KEYWORD_PRINT,
+    Engine, KEYWORD_DEBUG, KEYWORD_DUMP_AST, KEYWORD_EVAL, KEYWORD_PRINT, KEYWORD_TYPE_OF,
-    KEYWORD_TYPE_OF,
 };
 use crate::parser::{map_dynamic_to_expr, Expr, FnDef, ReturnType, Stmt, AST};
-use crate::scope::{Scope, ScopeEntry, VariableType};
+use crate::scope::{Entry as ScopeEntry, EntryType as ScopeEntryType, Scope};
 
 use crate::stdlib::{
     boxed::Box,
@@ -181,16 +180,15 @@ fn optimize_stmt<'a>(stmt: Stmt, state: &mut State<'a>, preserve_result: bool) -
             // Optimize each statement in the block
             let mut result: Vec<_> = block
                 .into_iter()
-                .map(|stmt| {
+                .map(|stmt| match stmt {
-                    if let Stmt::Const(name, value, pos) = stmt {
                     // Add constant into the state
+                    Stmt::Const(name, value, pos) => {
                         state.push_constant(&name, *value);
                         state.set_dirty();
                         Stmt::Noop(pos) // No need to keep constants
-                    } else {
-                        // Optimize the statement
-                        optimize_stmt(stmt, state, preserve_result)
                     }
+                    // Optimize the statement
+                    _ => optimize_stmt(stmt, state, preserve_result),
                 })
                 .collect();
 
@@ -446,13 +444,13 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
                 && args.iter().all(|expr| expr.is_constant()) // all arguments are constants
         => {
             // First search in script-defined functions (can override built-in)
-            if state.engine.script_functions.binary_search_by(|f| f.compare(&id, args.len())).is_ok() {
+            if state.engine.fn_lib.has_function(&id, args.len()) {
                 // A script-defined function overrides the built-in function - do not make the call
                 return Expr::FunctionCall(id, args.into_iter().map(|a| optimize_expr(a, state)).collect(), def_value, pos);
             }
 
             let mut arg_values: Vec<_> = args.iter().map(Expr::get_constant_value).collect();
-            let call_args: FnCallArgs = arg_values.iter_mut().map(Dynamic::as_mut).collect();
+            let mut call_args: Vec<_> = arg_values.iter_mut().map(Dynamic::as_mut).collect();
 
             // Save the typename of the first argument if it is `type_of()`
             // This is to avoid `call_args` being passed into the closure
@@ -462,7 +460,7 @@ fn optimize_expr<'a>(expr: Expr, state: &mut State<'a>) -> Expr {
                 ""
             };
 
-            state.engine.call_ext_fn_raw(&id, call_args, pos).ok().map(|r|
+            state.engine.call_ext_fn_raw(&id, &mut call_args, pos).ok().map(|r|
                 r.or_else(|| {
                     if !arg_for_type_of.is_empty() {
                         // Handle `type_of()`
@@ -512,9 +510,9 @@ pub(crate) fn optimize<'a>(statements: Vec<Stmt>, engine: &Engine<'a>, scope: &S
     // Add constants from the scope into the state
     scope
         .iter()
-        .filter(|ScopeEntry { var_type, expr, .. }| {
+        .filter(|ScopeEntry { typ, expr, .. }| {
             // Get all the constants with definite constant expressions
-            *var_type == VariableType::Constant
+            *typ == ScopeEntryType::Constant
                 && expr.as_ref().map(Expr::is_constant).unwrap_or(false)
         })
         .for_each(|ScopeEntry { name, expr, .. }| {
@@ -566,7 +564,7 @@ pub(crate) fn optimize<'a>(statements: Vec<Stmt>, engine: &Engine<'a>, scope: &S
 
     // Add back the last statement unless it is a lone No-op
     if let Some(stmt) = last_stmt {
-        if result.len() > 0 || !matches!(stmt, Stmt::Noop(_)) {
+        if !result.is_empty() || !matches!(stmt, Stmt::Noop(_)) {
             result.push(stmt);
         }
     }
@@ -591,9 +589,7 @@ pub fn optimize_into_ast(
         functions
             .into_iter()
             .map(|mut fn_def| {
-                match engine.optimization_level {
+                if engine.optimization_level != OptimizationLevel::None {
-                    OptimizationLevel::None => (),
-                    OptimizationLevel::Simple | OptimizationLevel::Full => {
                     let pos = fn_def.body.position();
 
                     // Optimize the function body
@@ -602,9 +598,7 @@ pub fn optimize_into_ast(
                     // {} -> Noop
                     fn_def.body = match body.pop().unwrap_or_else(|| Stmt::Noop(pos)) {
                         // { return val; } -> val
-                            Stmt::ReturnWithVal(Some(val), ReturnType::Return, _) => {
+                        Stmt::ReturnWithVal(Some(val), ReturnType::Return, _) => Stmt::Expr(val),
-                                Stmt::Expr(val)
-                            }
                         // { return; } -> ()
                         Stmt::ReturnWithVal(None, ReturnType::Return, pos) => {
                             Stmt::Expr(Box::new(Expr::Unit(pos)))
@@ -613,7 +607,7 @@ pub fn optimize_into_ast(
                         stmt => stmt,
                     };
                 }
-                }
+
                 Arc::new(fn_def)
             })
             .collect(),

src/result.rs

@@ -60,6 +60,8 @@ pub enum EvalAltResult {
     ErrorDotExpr(String, Position),
     /// Arithmetic error encountered. Wrapped value is the error message.
     ErrorArithmetic(String, Position),
+    /// Call stack over maximum limit.
+    ErrorStackOverflow(Position),
     /// Run-time error encountered. Wrapped value is the error message.
     ErrorRuntime(String, Position),
     /// Breaking out of loops - not an error if within a loop.
@@ -105,6 +107,7 @@ impl EvalAltResult {
             Self::ErrorReadingScriptFile(_, _) => "Cannot read from script file",
             Self::ErrorDotExpr(_, _) => "Malformed dot expression",
             Self::ErrorArithmetic(_, _) => "Arithmetic error",
+            Self::ErrorStackOverflow(_) => "Stack overflow",
             Self::ErrorRuntime(_, _) => "Runtime error",
             Self::ErrorLoopBreak(_) => "Break statement not inside a loop",
             Self::Return(_, _) => "[Not Error] Function returns value",
@@ -131,6 +134,7 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorDotExpr(s, pos) if !s.is_empty() => write!(f, "{} {} ({})", desc, s, pos),
             Self::ErrorDotExpr(_, pos) => write!(f, "{} ({})", desc, pos),
             Self::ErrorArithmetic(s, pos) => write!(f, "{} ({})", s, pos),
+            Self::ErrorStackOverflow(pos) => write!(f, "{} ({})", desc, pos),
             Self::ErrorRuntime(s, pos) => {
                 write!(f, "{} ({})", if s.is_empty() { desc } else { s }, pos)
             }
@@ -230,13 +234,16 @@ impl EvalAltResult {
             | Self::ErrorMismatchOutputType(_, pos)
             | Self::ErrorDotExpr(_, pos)
             | Self::ErrorArithmetic(_, pos)
+            | Self::ErrorStackOverflow(pos)
             | Self::ErrorRuntime(_, pos)
             | Self::ErrorLoopBreak(pos)
             | Self::Return(_, pos) => *pos,
         }
     }
 
-    pub(crate) fn set_position(&mut self, new_position: Position) {
+    /// Consume the current `EvalAltResult` and return a new one
+    /// with the specified `Position`.
+    pub(crate) fn set_position(mut self, new_position: Position) -> Self {
         match self {
             #[cfg(not(feature = "no_std"))]
             Self::ErrorReadingScriptFile(_, _) => (),
@@ -258,9 +265,12 @@ impl EvalAltResult {
             | Self::ErrorMismatchOutputType(_, ref mut pos)
             | Self::ErrorDotExpr(_, ref mut pos)
             | Self::ErrorArithmetic(_, ref mut pos)
+            | Self::ErrorStackOverflow(ref mut pos)
             | Self::ErrorRuntime(_, ref mut pos)
             | Self::ErrorLoopBreak(ref mut pos)
             | Self::Return(_, ref mut pos) => *pos = new_position,
         }
+
+        self
     }
 }

src/scope.rs

@@ -10,32 +10,34 @@ use crate::stdlib::{
     vec::Vec,
 };
 
-/// Type of a variable in the Scope.
+/// Type of an entry in the Scope.
 #[derive(Debug, Eq, PartialEq, Hash, Copy, Clone)]
-pub enum VariableType {
+pub enum EntryType {
-    /// Normal variable.
+    /// Normal value.
     Normal,
     /// Immutable constant value.
     Constant,
 }
 
 /// An entry in the Scope.
-pub struct ScopeEntry<'a> {
+#[derive(Debug, Clone)]
-    /// Name of the variable.
+pub struct Entry<'a> {
+    /// Name of the entry.
     pub name: Cow<'a, str>,
-    /// Type of the variable.
+    /// Type of the entry.
-    pub var_type: VariableType,
+    pub typ: EntryType,
-    /// Current value of the variable.
+    /// Current value of the entry.
     pub value: Dynamic,
     /// A constant expression if the initial value matches one of the recognized types.
     pub expr: Option<Expr>,
 }
 
 /// Information about a particular entry in the Scope.
-pub(crate) struct ScopeSource<'a> {
+#[derive(Debug, Hash, Copy, Clone)]
+pub(crate) struct EntryRef<'a> {
     pub name: &'a str,
-    pub idx: usize,
+    pub index: usize,
-    pub var_type: VariableType,
+    pub typ: EntryType,
 }
 
 /// A type containing information about the current scope.
@@ -57,9 +59,9 @@ pub(crate) struct ScopeSource<'a> {
 /// # }
 /// ```
 ///
-/// When searching for variables, newly-added variables are found before similarly-named but older variables,
+/// When searching for entries, newly-added entries are found before similarly-named but older entries,
-/// allowing for automatic _shadowing_ of variables.
+/// allowing for automatic _shadowing_.
-pub struct Scope<'a>(Vec<ScopeEntry<'a>>);
+pub struct Scope<'a>(Vec<Entry<'a>>);
 
 impl<'a> Scope<'a> {
     /// Create a new Scope.
@@ -72,24 +74,24 @@ impl<'a> Scope<'a> {
         self.0.clear();
     }
 
-    /// Get the number of variables inside the Scope.
+    /// Get the number of entries inside the Scope.
     pub fn len(&self) -> usize {
         self.0.len()
     }
 
-    /// Add (push) a new variable to the Scope.
+    /// Is the Scope empty?
+    pub fn is_empty(&self) -> bool {
+        self.0.len() == 0
+    }
+
+    /// Add (push) a new entry to the Scope.
     pub fn push<K: Into<Cow<'a, str>>, T: Any + Clone>(&mut self, name: K, value: T) {
-        let value = value.into_dynamic();
+        self.push_dynamic_value(name, EntryType::Normal, value.into_dynamic(), false);
+    }
 
-        // Map into constant expressions
+    /// Add (push) a new `Dynamic` entry to the Scope.
-        //let (expr, value) = map_dynamic_to_expr(value, Position::none());
+    pub fn push_dynamic<K: Into<Cow<'a, str>>>(&mut self, name: K, value: Dynamic) {
-
+        self.push_dynamic_value(name, EntryType::Normal, value, false);
-        self.0.push(ScopeEntry {
-            name: name.into(),
-            var_type: VariableType::Normal,
-            value,
-            expr: None,
-        });
     }
 
     /// Add (push) a new constant to the Scope.
@@ -99,85 +101,75 @@ impl<'a> Scope<'a> {
     /// However, in order to be used for optimization, constants must be in one of the recognized types:
     /// `INT` (default to `i64`, `i32` if `only_i32`), `f64`, `String`, `char` and `bool`.
     pub fn push_constant<K: Into<Cow<'a, str>>, T: Any + Clone>(&mut self, name: K, value: T) {
-        let value = value.into_dynamic();
+        self.push_dynamic_value(name, EntryType::Constant, value.into_dynamic(), true);
-
-        // Map into constant expressions
-        let (expr, value) = map_dynamic_to_expr(value, Position::none());
-
-        self.0.push(ScopeEntry {
-            name: name.into(),
-            var_type: VariableType::Constant,
-            value,
-            expr,
-        });
     }
 
-    /// Add (push) a new variable with a `Dynamic` value to the Scope.
+    /// Add (push) a new constant with a `Dynamic` value to the Scope.
-    pub(crate) fn push_dynamic<K: Into<Cow<'a, str>>>(
+    ///
+    /// Constants are immutable and cannot be assigned to.  Their values never change.
+    /// Constants propagation is a technique used to optimize an AST.
+    /// However, in order to be used for optimization, the `Dynamic` value must be in one of the
+    /// recognized types:
+    /// `INT` (default to `i64`, `i32` if `only_i32`), `f64`, `String`, `char` and `bool`.
+    pub fn push_constant_dynamic<K: Into<Cow<'a, str>>>(&mut self, name: K, value: Dynamic) {
+        self.push_dynamic_value(name, EntryType::Constant, value, true);
+    }
+
+    /// Add (push) a new entry with a `Dynamic` value to the Scope.
+    pub(crate) fn push_dynamic_value<K: Into<Cow<'a, str>>>(
         &mut self,
         name: K,
-        var_type: VariableType,
+        entry_type: EntryType,
         value: Dynamic,
+        map_expr: bool,
     ) {
-        let (expr, value) = map_dynamic_to_expr(value, Position::none());
+        let (expr, value) = if map_expr {
+            map_dynamic_to_expr(value, Position::none())
+        } else {
+            (None, value)
+        };
 
-        self.0.push(ScopeEntry {
+        self.0.push(Entry {
             name: name.into(),
-            var_type,
+            typ: entry_type,
             value,
             expr,
         });
     }
 
-    /// Remove (pop) the last variable from the Scope.
-    pub fn pop(&mut self) -> Option<(String, VariableType, Dynamic)> {
-        self.0.pop().map(
-            |ScopeEntry {
-                 name,
-                 var_type,
-                 value,
-                 ..
-             }| (name.to_string(), var_type, value),
-        )
-    }
-
     /// Truncate (rewind) the Scope to a previous size.
     pub fn rewind(&mut self, size: usize) {
         self.0.truncate(size);
     }
 
-    /// Does the scope contain the variable?
+    /// Does the scope contain the entry?
     pub fn contains(&self, key: &str) -> bool {
         self.0
             .iter()
             .enumerate()
             .rev() // Always search a Scope in reverse order
-            .find(|(_, ScopeEntry { name, .. })| name == key)
+            .any(|(_, Entry { name, .. })| name == key)
-            .is_some()
     }
 
-    /// Find a variable in the Scope, starting from the last.
+    /// Find an entry in the Scope, starting from the last.
-    pub(crate) fn get(&self, key: &str) -> Option<(ScopeSource, Dynamic)> {
+    pub(crate) fn get(&self, key: &str) -> Option<(EntryRef, Dynamic)> {
         self.0
             .iter()
             .enumerate()
             .rev() // Always search a Scope in reverse order
-            .find(|(_, ScopeEntry { name, .. })| name == key)
+            .find(|(_, Entry { name, .. })| name == key)
             .map(
                 |(
                     i,
-                    ScopeEntry {
+                    Entry {
-                        name,
+                        name, typ, value, ..
-                        var_type,
-                        value,
-                        ..
                     },
                 )| {
                     (
-                        ScopeSource {
+                        EntryRef {
                             name: name.as_ref(),
-                            idx: i,
+                            index: i,
-                            var_type: *var_type,
+                            typ: *typ,
                         },
                         value.clone(),
                     )
@@ -185,54 +177,60 @@ impl<'a> Scope<'a> {
             )
     }
 
-    /// Get the value of a variable in the Scope, starting from the last.
+    /// Get the value of an entry in the Scope, starting from the last.
     pub fn get_value<T: Any + Clone>(&self, key: &str) -> Option<T> {
         self.0
             .iter()
             .enumerate()
             .rev() // Always search a Scope in reverse order
-            .find(|(_, ScopeEntry { name, .. })| name == key)
+            .find(|(_, Entry { name, .. })| name == key)
-            .and_then(|(_, ScopeEntry { value, .. })| value.downcast_ref::<T>())
+            .and_then(|(_, Entry { value, .. })| value.downcast_ref::<T>())
             .map(T::clone)
     }
 
-    /// Get a mutable reference to a variable in the Scope.
+    /// Get a mutable reference to an entry in the Scope.
-    pub(crate) fn get_mut(&mut self, name: &str, index: usize) -> &mut Dynamic {
+    pub(crate) fn get_mut(&mut self, key: EntryRef) -> &mut Dynamic {
-        let entry = self.0.get_mut(index).expect("invalid index in Scope");
+        let entry = self.0.get_mut(key.index).expect("invalid index in Scope");
+        assert_eq!(entry.typ, key.typ, "entry type not matched");
 
         // assert_ne!(
-        //     entry.var_type,
+        //     entry.typ,
-        //     VariableType::Constant,
+        //     EntryType::Constant,
-        //     "get mut of constant variable"
+        //     "get mut of constant entry"
         // );
-        assert_eq!(entry.name, name, "incorrect key at Scope entry");
+        assert_eq!(entry.name, key.name, "incorrect key at Scope entry");
 
         &mut entry.value
     }
 
-    /// Get a mutable reference to a variable in the Scope and downcast it to a specific type
+    /// Get a mutable reference to an entry in the Scope and downcast it to a specific type
-    #[cfg(not(feature = "no_index"))]
+    pub(crate) fn get_mut_by_type<T: Any + Clone>(&mut self, key: EntryRef) -> &mut T {
-    pub(crate) fn get_mut_by_type<T: Any + Clone>(&mut self, name: &str, index: usize) -> &mut T {
+        self.get_mut(key)
-        self.get_mut(name, index)
             .downcast_mut::<T>()
             .expect("wrong type cast")
     }
 
-    /// Get an iterator to variables in the Scope.
+    /// Get an iterator to entries in the Scope.
-    pub fn iter(&self) -> impl Iterator<Item = &ScopeEntry> {
+    pub fn iter(&self) -> impl Iterator<Item = &Entry> {
         self.0.iter().rev() // Always search a Scope in reverse order
     }
 }
 
-impl<'a, K> iter::Extend<(K, VariableType, Dynamic)> for Scope<'a>
+impl Default for Scope<'_> {
+    fn default() -> Self {
+        Scope::new()
+    }
+}
+
+impl<'a, K> iter::Extend<(K, EntryType, Dynamic)> for Scope<'a>
 where
     K: Into<Cow<'a, str>>,
 {
-    fn extend<T: IntoIterator<Item = (K, VariableType, Dynamic)>>(&mut self, iter: T) {
+    fn extend<T: IntoIterator<Item = (K, EntryType, Dynamic)>>(&mut self, iter: T) {
         self.0
-            .extend(iter.into_iter().map(|(name, var_type, value)| ScopeEntry {
+            .extend(iter.into_iter().map(|(name, typ, value)| Entry {
                 name: name.into(),
-                var_type,
+                typ,
                 value,
                 expr: None,
             }));

tests/call_fn.rs

@@ -1,5 +1,22 @@
 #![cfg(not(feature = "no_function"))]
-use rhai::{Engine, EvalAltResult, INT};
+use rhai::{Engine, EvalAltResult, ParseErrorType, INT};
+
+#[test]
+fn test_fn() -> Result<(), EvalAltResult> {
+    let engine = Engine::new();
+
+    // Expect duplicated parameters error
+    match engine
+        .compile("fn hello(x, x) { x }")
+        .expect_err("should be error")
+        .error_type()
+    {
+        ParseErrorType::FnDuplicateParam(f, p) if f == "hello" && p == "x" => (),
+        _ => assert!(false, "wrong error"),
+    }
+
+    Ok(())
+}
 
 #[test]
 fn test_call_fn() -> Result<(), EvalAltResult> {

tests/expressions.rs

@@ -12,14 +12,64 @@ fn test_expressions() -> Result<(), EvalAltResult> {
         engine.eval_expression_with_scope::<INT>(&mut scope, "2 + (x + 10) * 2")?,
         42
     );
+    assert_eq!(
+        engine.eval_expression_with_scope::<INT>(&mut scope, "if x > 0 { 42 } else { 123 }")?,
+        42
+    );
 
     assert!(engine.eval_expression::<()>("40 + 2;").is_err());
     assert!(engine.eval_expression::<()>("40 + { 2 }").is_err());
     assert!(engine.eval_expression::<()>("x = 42").is_err());
     assert!(engine.compile_expression("let x = 42").is_err());
-    assert!(engine
+
-        .eval_expression_with_scope::<INT>(&mut scope, "if x > 0 { 42 } else { 123 }")
+    Ok(())
-        .is_err());
+}
+
+/// This example taken from https://github.com/jonathandturner/rhai/issues/115
+#[test]
+fn test_expressions_eval() -> Result<(), EvalAltResult> {
+    #[derive(Debug, Clone)]
+    struct AGENT {
+        pub gender: String,
+        pub age: INT,
+    }
+
+    impl AGENT {
+        pub fn get_gender(&mut self) -> String {
+            self.gender.clone()
+        }
+        pub fn get_age(&mut self) -> INT {
+            self.age
+        }
+    }
+
+    // This is your agent
+    let my_agent = AGENT {
+        gender: "male".into(),
+        age: 42,
+    };
+
+    // Create the engine
+    let mut engine = Engine::new();
+
+    // Register your AGENT type
+    engine.register_type_with_name::<AGENT>("AGENT");
+    engine.register_get("gender", AGENT::get_gender);
+    engine.register_get("age", AGENT::get_age);
+
+    // Create your context, add the agent as a constant
+    let mut scope = Scope::new();
+    scope.push_constant("agent", my_agent);
+
+    // Evaluate the expression
+    let result: bool = engine.eval_expression_with_scope(
+        &mut scope,
+        r#"
+                agent.age > 10 && agent.gender == "male"
+        "#,
+    )?;
+
+    assert_eq!(result, true);
 
     Ok(())
 }

tests/float.rs

@@ -1,5 +1,7 @@
 #![cfg(not(feature = "no_float"))]
-use rhai::{Engine, EvalAltResult, RegisterFn};
+use rhai::{Engine, EvalAltResult, RegisterFn, FLOAT};
+
+const EPSILON: FLOAT = 0.000_000_000_1;
 
 #[test]
 fn test_float() -> Result<(), EvalAltResult> {
@@ -13,7 +15,7 @@ fn test_float() -> Result<(), EvalAltResult> {
         engine.eval::<bool>("let x = 0.0; let y = 1.0; x > y")?,
         false
     );
-    assert_eq!(engine.eval::<f64>("let x = 9.9999; x")?, 9.9999);
+    assert!((engine.eval::<FLOAT>("let x = 9.9999; x")? - 9.9999 as FLOAT).abs() < EPSILON);
 
     Ok(())
 }
@@ -51,13 +53,12 @@ fn struct_with_float() -> Result<(), EvalAltResult> {
     engine.register_fn("update", TestStruct::update);
     engine.register_fn("new_ts", TestStruct::new);
 
-    assert_eq!(
+    assert!(
-        engine.eval::<f64>("let ts = new_ts(); ts.update(); ts.x")?,
+        (engine.eval::<FLOAT>("let ts = new_ts(); ts.update(); ts.x")? - 6.789).abs() < EPSILON
-        6.789
     );
-    assert_eq!(
+    assert!(
-        engine.eval::<f64>("let ts = new_ts(); ts.x = 10.1001; ts.x")?,
+        (engine.eval::<FLOAT>("let ts = new_ts(); ts.x = 10.1001; ts.x")? - 10.1001).abs()
-        10.1001
+            < EPSILON
     );
 
     Ok(())

tests/if_block.rs

@@ -27,3 +27,21 @@ fn test_if() -> Result<(), EvalAltResult> {
 
     Ok(())
 }
+
+#[test]
+fn test_if_expr() -> Result<(), EvalAltResult> {
+    let mut engine = Engine::new();
+
+    assert_eq!(
+        engine.eval::<INT>(
+            r"
+                let x = 42;
+                let y = 1 + if x > 40 { 100 } else { 0 } / x;
+                y
+        "
+        )?,
+        3
+    );
+
+    Ok(())
+}

tests/math.rs

@@ -13,7 +13,7 @@ fn test_math() -> Result<(), EvalAltResult> {
     #[cfg(not(feature = "only_i32"))]
     assert_eq!(
         engine.eval::<INT>("(-9223372036854775807).abs()")?,
-        9223372036854775807
+        9_223_372_036_854_775_807
     );
 
     #[cfg(feature = "only_i32")]

tests/method_call.rs

@@ -25,8 +25,10 @@ fn test_method_call() -> Result<(), EvalAltResult> {
     engine.register_fn("new_ts", TestStruct::new);
 
     let ts = engine.eval::<TestStruct>("let x = new_ts(); x.update(); x")?;
-
     assert_eq!(ts.x, 1001);
 
+    let ts = engine.eval::<TestStruct>("let x = new_ts(); update(x); x")?;
+    assert_eq!(ts.x, 1);
+
     Ok(())
 }

tests/power_of.rs

@@ -4,7 +4,7 @@ use rhai::{Engine, EvalAltResult, INT};
 use rhai::FLOAT;
 
 #[cfg(not(feature = "no_float"))]
-const EPSILON: FLOAT = 0.0000000001;
+const EPSILON: FLOAT = 0.000_000_000_1;
 
 #[test]
 fn test_power_of() -> Result<(), EvalAltResult> {
@@ -16,11 +16,11 @@ fn test_power_of() -> Result<(), EvalAltResult> {
     #[cfg(not(feature = "no_float"))]
     {
         assert!(
-            (engine.eval::<FLOAT>("2.2 ~ 3.3")? - 13.489468760533386 as FLOAT).abs() <= EPSILON
+            (engine.eval::<FLOAT>("2.2 ~ 3.3")? - 13.489_468_760_533_386 as FLOAT).abs() <= EPSILON
         );
-        assert_eq!(engine.eval::<FLOAT>("2.0~-2.0")?, 0.25 as FLOAT);
+        assert!((engine.eval::<FLOAT>("2.0~-2.0")? - 0.25 as FLOAT).abs() < EPSILON);
-        assert_eq!(engine.eval::<FLOAT>("(-2.0~-2.0)")?, 0.25 as FLOAT);
+        assert!((engine.eval::<FLOAT>("(-2.0~-2.0)")? - 0.25 as FLOAT).abs() < EPSILON);
-        assert_eq!(engine.eval::<FLOAT>("(-2.0~-2)")?, 0.25 as FLOAT);
+        assert!((engine.eval::<FLOAT>("(-2.0~-2)")? - 0.25 as FLOAT).abs() < EPSILON);
         assert_eq!(engine.eval::<INT>("4~3")?, 64);
     }
 
@@ -37,20 +37,18 @@ fn test_power_of_equals() -> Result<(), EvalAltResult> {
     #[cfg(not(feature = "no_float"))]
     {
         assert!(
-            (engine.eval::<FLOAT>("let x = 2.2; x ~= 3.3; x")? - 13.489468760533386 as FLOAT).abs()
+            (engine.eval::<FLOAT>("let x = 2.2; x ~= 3.3; x")? - 13.489_468_760_533_386 as FLOAT)
+                .abs()
                 <= EPSILON
         );
-        assert_eq!(
+        assert!(
-            engine.eval::<FLOAT>("let x = 2.0; x ~= -2.0; x")?,
+            (engine.eval::<FLOAT>("let x = 2.0; x ~= -2.0; x")? - 0.25 as FLOAT).abs() < EPSILON
-            0.25 as FLOAT
         );
-        assert_eq!(
+        assert!(
-            engine.eval::<FLOAT>("let x = -2.0; x ~= -2.0; x")?,
+            (engine.eval::<FLOAT>("let x = -2.0; x ~= -2.0; x")? - 0.25 as FLOAT).abs() < EPSILON
-            0.25 as FLOAT
         );
-        assert_eq!(
+        assert!(
-            engine.eval::<FLOAT>("let x = -2.0; x ~= -2; x")?,
+            (engine.eval::<FLOAT>("let x = -2.0; x ~= -2; x")? - 0.25 as FLOAT).abs() < EPSILON
-            0.25 as FLOAT
         );
         assert_eq!(engine.eval::<INT>("let x =4; x ~= 3; x")?, 64);
     }

tests/unit.rs

@@ -3,7 +3,7 @@ use rhai::{Engine, EvalAltResult};
 #[test]
 fn test_unit() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
-    assert_eq!(engine.eval::<()>("let x = (); x")?, ());
+    engine.eval::<()>("let x = (); x")?;
     Ok(())
 }
 
@@ -17,6 +17,6 @@ fn test_unit_eq() -> Result<(), EvalAltResult> {
 #[test]
 fn test_unit_with_spaces() -> Result<(), EvalAltResult> {
     let mut engine = Engine::new();
-    assert_eq!(engine.eval::<()>("let x = ( ); x")?, ());
+    engine.eval::<()>("let x = ( ); x")?;
     Ok(())
 }

tests/var_scope.rs

@@ -9,7 +9,7 @@ fn test_var_scope() -> Result<(), EvalAltResult> {
     assert_eq!(engine.eval_with_scope::<INT>(&mut scope, "x")?, 9);
     engine.eval_with_scope::<()>(&mut scope, "x = x + 1; x = x + 2;")?;
     assert_eq!(engine.eval_with_scope::<INT>(&mut scope, "x")?, 12);
-    assert_eq!(engine.eval_with_scope::<()>(&mut scope, "{let x = 3}")?, ());
+    engine.eval_with_scope::<()>(&mut scope, "{let x = 3}")?;
     assert_eq!(engine.eval_with_scope::<INT>(&mut scope, "x")?, 12);
 
     Ok(())