diff --git a/README.md b/README.md
index 8edae03a..7cfdb6d4 100644
--- a/README.md
+++ b/README.md
@@ -203,7 +203,7 @@ To get going with Rhai, create an instance of the scripting engine via `Engine::
 ```rust
 use rhai::{Engine, EvalAltResult};
 
-fn main() -> Result<(), EvalAltResult>
+fn main() -> Result<(), Box<EvalAltResult>>
 {
     let engine = Engine::new();
 
@@ -324,7 +324,7 @@ let script = "fn calc(x, y) { x + y.len() < 42 }";
 //   1) a tuple made up of the types of the script function's parameters
 //   2) the return type of the script function
 //
-// 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, EvalAltResult>> and is callable!
+// 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, Box<EvalAltResult>>> and is callable!
 let func = Func::<(i64, String), bool>::create_from_script(
 //                ^^^^^^^^^^^^^ function parameter types in tuple
 
@@ -340,7 +340,7 @@ schedule_callback(func);                        // pass it as a callback to anot
 // Although there is nothing you can't do by manually writing out the closure yourself...
 let engine = Engine::new();
 let ast = engine.compile(script)?;
-schedule_callback(Box::new(move |x: i64, y: String| -> Result<bool, EvalAltResult> {
+schedule_callback(Box::new(move |x: i64, y: String| -> Result<bool, Box<EvalAltResult>> {
     engine.call_fn(&mut Scope::new(), &ast, "calc", (x, y))
 }));
 ```
@@ -560,12 +560,12 @@ Traits
 
 A number of traits, under the `rhai::` module namespace, provide additional functionalities.
 
-| Trait               | Description                                                                       | Methods                                 |
-| ------------------- | --------------------------------------------------------------------------------- | --------------------------------------- |
-| `RegisterFn`        | Trait for registering functions                                                   | `register_fn`                           |
-| `RegisterDynamicFn` | Trait for registering functions returning [`Dynamic`]                             | `register_dynamic_fn`                   |
-| `RegisterResultFn`  | Trait for registering fallible functions returning `Result<`_T_`, EvalAltResult>` | `register_result_fn`                    |
-| `Func`              | Trait for creating anonymous functions from script                                | `create_from_ast`, `create_from_script` |
+| Trait               | Description                                                                            | Methods                                 |
+| ------------------- | -------------------------------------------------------------------------------------- | --------------------------------------- |
+| `RegisterFn`        | Trait for registering functions                                                        | `register_fn`                           |
+| `RegisterDynamicFn` | Trait for registering functions returning [`Dynamic`]                                  | `register_dynamic_fn`                   |
+| `RegisterResultFn`  | Trait for registering fallible functions returning `Result<`_T_`, Box<EvalAltResult>>` | `register_result_fn`                    |
+| `Func`              | Trait for creating anonymous functions from script                                     | `create_from_ast`, `create_from_script` |
 
 Working with functions
 ----------------------
@@ -588,7 +588,7 @@ fn get_an_any() -> Dynamic {
     Dynamic::from(42_i64)
 }
 
-fn main() -> Result<(), EvalAltResult>
+fn main() -> Result<(), Box<EvalAltResult>>
 {
     let engine = Engine::new();
 
@@ -657,18 +657,20 @@ Fallible functions
 If a function is _fallible_ (i.e. it returns a `Result<_, Error>`), it can be registered with `register_result_fn`
 (using the `RegisterResultFn` trait).
 
-The function must return `Result<_, EvalAltResult>`. `EvalAltResult` implements `From<&str>` and `From<String>` etc.
-and the error text gets converted into `EvalAltResult::ErrorRuntime`.
+The function must return `Result<_, Box<EvalAltResult>>`. `Box<EvalAltResult>` implements `From<&str>` and `From<String>` etc.
+and the error text gets converted into `Box<EvalAltResult::ErrorRuntime>`.
+
+The error values are `Box`-ed in order to reduce memory footprint of the error path, which should be hit rarely.
 
 ```rust
 use rhai::{Engine, EvalAltResult, Position};
 use rhai::RegisterResultFn;                     // use 'RegisterResultFn' trait for 'register_result_fn'
 
 // Function that may fail
-fn safe_divide(x: i64, y: i64) -> Result<i64, EvalAltResult> {
+fn safe_divide(x: i64, y: i64) -> Result<i64, Box<EvalAltResult>> {
     if y == 0 {
         // Return an error if y is zero
-        Err("Division by zero!".into())         // short-cut to create EvalAltResult
+        Err("Division by zero!".into())         // short-cut to create Box<EvalAltResult::ErrorRuntime>
     } else {
         Ok(x / y)
     }
@@ -682,7 +684,7 @@ fn main()
     engine.register_result_fn("divide", safe_divide);
 
     if let Err(error) = engine.eval::<i64>("divide(40, 0)") {
-       println!("Error: {:?}", error);          // prints ErrorRuntime("Division by zero detected!", (1, 1)")
+       println!("Error: {:?}", *error);          // prints ErrorRuntime("Division by zero detected!", (1, 1)")
     }
 }
 ```
@@ -769,7 +771,7 @@ impl TestStruct {
     }
 }
 
-fn main() -> Result<(), EvalAltResult>
+fn main() -> Result<(), Box<EvalAltResult>>
 {
     let engine = Engine::new();
 
@@ -933,7 +935,7 @@ threaded through multiple invocations:
 ```rust
 use rhai::{Engine, Scope, EvalAltResult};
 
-fn main() -> Result<(), EvalAltResult>
+fn main() -> Result<(), Box<EvalAltResult>>
 {
     let engine = Engine::new();
 
@@ -1794,7 +1796,7 @@ return 123 + 456;           // returns 579
 Errors and `throw`-ing exceptions
 --------------------------------
 
-All of [`Engine`]'s evaluation/consuming methods return `Result<T, rhai::EvalAltResult>` with `EvalAltResult`
+All of [`Engine`]'s evaluation/consuming methods return `Result<T, Box<rhai::EvalAltResult>>` with `EvalAltResult`
 holding error information. To deliberately return an error during an evaluation, use the `throw` keyword.
 
 ```rust
diff --git a/examples/custom_types_and_methods.rs b/examples/custom_types_and_methods.rs
index c912520d..d152dc9b 100644
--- a/examples/custom_types_and_methods.rs
+++ b/examples/custom_types_and_methods.rs
@@ -16,7 +16,7 @@ impl TestStruct {
 }
 
 #[cfg(not(feature = "no_object"))]
-fn main() -> Result<(), EvalAltResult> {
+fn main() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     engine.register_type::<TestStruct>();
diff --git a/examples/hello.rs b/examples/hello.rs
index e999861f..edec8cb8 100644
--- a/examples/hello.rs
+++ b/examples/hello.rs
@@ -1,7 +1,7 @@
 use rhai::{packages::*, Engine, EvalAltResult, INT};
 use std::rc::Rc;
 
-fn main() -> Result<(), EvalAltResult> {
+fn main() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new_raw();
     engine.load_package(ArithmeticPackage::new().get());
 
diff --git a/examples/no_std.rs b/examples/no_std.rs
index ad9d9a8a..ed1647ef 100644
--- a/examples/no_std.rs
+++ b/examples/no_std.rs
@@ -2,7 +2,7 @@
 
 use rhai::{Engine, EvalAltResult, INT};
 
-fn main() -> Result<(), EvalAltResult> {
+fn main() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let result = engine.eval::<INT>("40 + 2")?;
diff --git a/examples/repl.rs b/examples/repl.rs
index 4c807814..4ae1c44f 100644
--- a/examples/repl.rs
+++ b/examples/repl.rs
@@ -157,7 +157,7 @@ fn main() {
             Ok(_) => (),
             Err(err) => {
                 println!();
-                print_error(&input, err);
+                print_error(&input, *err);
                 println!();
             }
         }
diff --git a/examples/reuse_scope.rs b/examples/reuse_scope.rs
index ab936656..a762ac8a 100644
--- a/examples/reuse_scope.rs
+++ b/examples/reuse_scope.rs
@@ -1,6 +1,6 @@
 use rhai::{Engine, EvalAltResult, Scope, INT};
 
-fn main() -> Result<(), EvalAltResult> {
+fn main() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     let mut scope = Scope::new();
 
diff --git a/examples/rhai_runner.rs b/examples/rhai_runner.rs
index 166e1c3e..2bc273e2 100644
--- a/examples/rhai_runner.rs
+++ b/examples/rhai_runner.rs
@@ -72,7 +72,7 @@ fn main() {
             eprintln!("{:=<1$}", "", filename.len());
             eprintln!("");
 
-            eprint_error(&contents, err);
+            eprint_error(&contents, *err);
         }
     }
 }
diff --git a/examples/simple_fn.rs b/examples/simple_fn.rs
index 796b8114..21f532ae 100644
--- a/examples/simple_fn.rs
+++ b/examples/simple_fn.rs
@@ -1,6 +1,6 @@
 use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
-fn main() -> Result<(), EvalAltResult> {
+fn main() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
 
     fn add(x: INT, y: INT) -> INT {
diff --git a/src/any.rs b/src/any.rs
index cb60384e..9c0e3288 100644
--- a/src/any.rs
+++ b/src/any.rs
@@ -450,7 +450,7 @@ impl Dynamic {
 
     /// Cast the `Dynamic` as the system integer type `INT` and return it.
     /// Returns the name of the actual type if the cast fails.
-    pub(crate) fn as_int(&self) -> Result<INT, &'static str> {
+    pub fn as_int(&self) -> Result<INT, &'static str> {
         match self.0 {
             Union::Int(n) => Ok(n),
             _ => Err(self.type_name()),
@@ -459,7 +459,7 @@ impl Dynamic {
 
     /// Cast the `Dynamic` as a `bool` and return it.
     /// Returns the name of the actual type if the cast fails.
-    pub(crate) fn as_bool(&self) -> Result<bool, &'static str> {
+    pub fn as_bool(&self) -> Result<bool, &'static str> {
         match self.0 {
             Union::Bool(b) => Ok(b),
             _ => Err(self.type_name()),
@@ -468,7 +468,7 @@ impl Dynamic {
 
     /// Cast the `Dynamic` as a `char` and return it.
     /// Returns the name of the actual type if the cast fails.
-    pub(crate) fn as_char(&self) -> Result<char, &'static str> {
+    pub fn as_char(&self) -> Result<char, &'static str> {
         match self.0 {
             Union::Char(n) => Ok(n),
             _ => Err(self.type_name()),
@@ -477,7 +477,7 @@ impl Dynamic {
 
     /// Cast the `Dynamic` as a string and return the string slice.
     /// Returns the name of the actual type if the cast fails.
-    pub(crate) fn as_str(&self) -> Result<&str, &'static str> {
+    pub fn as_str(&self) -> Result<&str, &'static str> {
         match &self.0 {
             Union::Str(s) => Ok(s),
             _ => Err(self.type_name()),
@@ -486,30 +486,36 @@ impl Dynamic {
 
     /// Convert the `Dynamic` into `String` and return it.
     /// Returns the name of the actual type if the cast fails.
-    pub(crate) fn take_string(self) -> Result<String, &'static str> {
+    pub fn take_string(self) -> Result<String, &'static str> {
         match self.0 {
             Union::Str(s) => Ok(*s),
             _ => Err(self.type_name()),
         }
     }
 
-    pub(crate) fn from_unit() -> Self {
+    /// Create a `Dynamic` from `()`.
+    pub fn from_unit() -> Self {
         Self(Union::Unit(()))
     }
-    pub(crate) fn from_bool(value: bool) -> Self {
+    /// Create a `Dynamic` from a `bool`.
+    pub fn from_bool(value: bool) -> Self {
         Self(Union::Bool(value))
     }
-    pub(crate) fn from_int(value: INT) -> Self {
+    /// Create a `Dynamic` from an `INT`.
+    pub fn from_int(value: INT) -> Self {
         Self(Union::Int(value))
     }
+    /// Create a `Dynamic` from a `FLOAT`. Not available under `no_float`.
     #[cfg(not(feature = "no_float"))]
     pub(crate) fn from_float(value: FLOAT) -> Self {
         Self(Union::Float(value))
     }
-    pub(crate) fn from_char(value: char) -> Self {
+    /// Create a `Dynamic` from a `char`.
+    pub fn from_char(value: char) -> Self {
         Self(Union::Char(value))
     }
-    pub(crate) fn from_string(value: String) -> Self {
+    /// Create a `Dynamic` from a `String`.
+    pub fn from_string(value: String) -> Self {
         Self(Union::Str(Box::new(value)))
     }
 }
diff --git a/src/api.rs b/src/api.rs
index 71a94b30..86cf39c0 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -76,7 +76,7 @@ impl Engine {
     ///     fn update(&mut self, offset: i64)   { self.field += offset; }
     /// }
     ///
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// let mut engine = Engine::new();
@@ -116,7 +116,7 @@ impl Engine {
     ///     fn new() -> Self { TestStruct { field: 1 } }
     /// }
     ///
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// let mut engine = Engine::new();
@@ -182,7 +182,7 @@ impl Engine {
     ///     fn get_field(&mut self) -> i64  { self.field }
     /// }
     ///
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// let mut engine = Engine::new();
@@ -224,7 +224,7 @@ impl Engine {
     ///     fn set_field(&mut self, new_val: i64)   { self.field = new_val; }
     /// }
     ///
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// let mut engine = Engine::new();
@@ -275,7 +275,7 @@ impl Engine {
     ///     fn set_field(&mut self, new_val: i64)   { self.field = new_val; }
     /// }
     ///
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// let mut engine = Engine::new();
@@ -310,7 +310,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -324,7 +324,7 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn compile(&self, script: &str) -> Result<AST, ParseError> {
+    pub fn compile(&self, script: &str) -> Result<AST, Box<ParseError>> {
         self.compile_with_scope(&Scope::new(), script)
     }
 
@@ -335,7 +335,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # #[cfg(not(feature = "no_optimize"))]
     /// # {
     /// use rhai::{Engine, Scope, OptimizationLevel};
@@ -365,7 +365,7 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn compile_with_scope(&self, scope: &Scope, script: &str) -> Result<AST, ParseError> {
+    pub fn compile_with_scope(&self, scope: &Scope, script: &str) -> Result<AST, Box<ParseError>> {
         self.compile_with_scope_and_optimization_level(scope, script, self.optimization_level)
     }
 
@@ -375,22 +375,22 @@ impl Engine {
         scope: &Scope,
         script: &str,
         optimization_level: OptimizationLevel,
-    ) -> Result<AST, ParseError> {
+    ) -> Result<AST, Box<ParseError>> {
         let scripts = [script];
         let stream = lex(&scripts);
-        parse(&mut stream.peekable(), self, scope, optimization_level).map_err(|err| *err)
+        parse(&mut stream.peekable(), self, scope, optimization_level)
     }
 
     /// Read the contents of a file into a string.
     #[cfg(not(feature = "no_std"))]
-    fn read_file(path: PathBuf) -> Result<String, EvalAltResult> {
+    fn read_file(path: PathBuf) -> Result<String, Box<EvalAltResult>> {
         let mut f = File::open(path.clone())
-            .map_err(|err| EvalAltResult::ErrorReadingScriptFile(path.clone(), err))?;
+            .map_err(|err| Box::new(EvalAltResult::ErrorReadingScriptFile(path.clone(), err)))?;
 
         let mut contents = String::new();
 
         f.read_to_string(&mut contents)
-            .map_err(|err| EvalAltResult::ErrorReadingScriptFile(path.clone(), err))?;
+            .map_err(|err| Box::new(EvalAltResult::ErrorReadingScriptFile(path.clone(), err)))?;
 
         Ok(contents)
     }
@@ -400,7 +400,7 @@ impl Engine {
     /// # Example
     ///
     /// ```no_run
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -416,7 +416,7 @@ impl Engine {
     /// # }
     /// ```
     #[cfg(not(feature = "no_std"))]
-    pub fn compile_file(&self, path: PathBuf) -> Result<AST, EvalAltResult> {
+    pub fn compile_file(&self, path: PathBuf) -> Result<AST, Box<EvalAltResult>> {
         self.compile_file_with_scope(&Scope::new(), path)
     }
 
@@ -427,7 +427,7 @@ impl Engine {
     /// # Example
     ///
     /// ```no_run
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # #[cfg(not(feature = "no_optimize"))]
     /// # {
     /// use rhai::{Engine, Scope, OptimizationLevel};
@@ -455,7 +455,7 @@ impl Engine {
         &self,
         scope: &Scope,
         path: PathBuf,
-    ) -> Result<AST, EvalAltResult> {
+    ) -> Result<AST, Box<EvalAltResult>> {
         Self::read_file(path).and_then(|contents| Ok(self.compile_with_scope(scope, &contents)?))
     }
 
@@ -467,7 +467,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -483,7 +483,7 @@ impl Engine {
     /// # }
     /// ```
     #[cfg(not(feature = "no_object"))]
-    pub fn parse_json(&self, json: &str, has_null: bool) -> Result<Map, EvalAltResult> {
+    pub fn parse_json(&self, json: &str, has_null: bool) -> Result<Map, Box<EvalAltResult>> {
         let mut scope = Scope::new();
 
         // Trims the JSON string and add a '#' in front
@@ -510,7 +510,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -524,7 +524,7 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn compile_expression(&self, script: &str) -> Result<AST, ParseError> {
+    pub fn compile_expression(&self, script: &str) -> Result<AST, Box<ParseError>> {
         self.compile_expression_with_scope(&Scope::new(), script)
     }
 
@@ -537,7 +537,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # #[cfg(not(feature = "no_optimize"))]
     /// # {
     /// use rhai::{Engine, Scope, OptimizationLevel};
@@ -571,12 +571,11 @@ impl Engine {
         &self,
         scope: &Scope,
         script: &str,
-    ) -> Result<AST, ParseError> {
+    ) -> Result<AST, Box<ParseError>> {
         let scripts = [script];
         let stream = lex(&scripts);
 
         parse_global_expr(&mut stream.peekable(), self, scope, self.optimization_level)
-            .map_err(|err| *err)
     }
 
     /// Evaluate a script file.
@@ -584,7 +583,7 @@ impl Engine {
     /// # Example
     ///
     /// ```no_run
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -595,7 +594,7 @@ impl Engine {
     /// # }
     /// ```
     #[cfg(not(feature = "no_std"))]
-    pub fn eval_file<T: Variant + Clone>(&self, path: PathBuf) -> Result<T, EvalAltResult> {
+    pub fn eval_file<T: Variant + Clone>(&self, path: PathBuf) -> Result<T, Box<EvalAltResult>> {
         Self::read_file(path).and_then(|contents| self.eval::<T>(&contents))
     }
 
@@ -604,7 +603,7 @@ impl Engine {
     /// # Example
     ///
     /// ```no_run
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Scope};
     ///
     /// let engine = Engine::new();
@@ -623,7 +622,7 @@ impl Engine {
         &self,
         scope: &mut Scope,
         path: PathBuf,
-    ) -> Result<T, EvalAltResult> {
+    ) -> Result<T, Box<EvalAltResult>> {
         Self::read_file(path).and_then(|contents| self.eval_with_scope::<T>(scope, &contents))
     }
 
@@ -632,7 +631,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -641,7 +640,7 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn eval<T: Variant + Clone>(&self, script: &str) -> Result<T, EvalAltResult> {
+    pub fn eval<T: Variant + Clone>(&self, script: &str) -> Result<T, Box<EvalAltResult>> {
         self.eval_with_scope(&mut Scope::new(), script)
     }
 
@@ -650,7 +649,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Scope};
     ///
     /// let engine = Engine::new();
@@ -671,7 +670,7 @@ impl Engine {
         &self,
         scope: &mut Scope,
         script: &str,
-    ) -> Result<T, EvalAltResult> {
+    ) -> Result<T, Box<EvalAltResult>> {
         // Since the AST will be thrown away afterwards, don't bother to optimize it
         let ast =
             self.compile_with_scope_and_optimization_level(scope, script, OptimizationLevel::None)?;
@@ -683,7 +682,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -692,7 +691,10 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn eval_expression<T: Variant + Clone>(&self, script: &str) -> Result<T, EvalAltResult> {
+    pub fn eval_expression<T: Variant + Clone>(
+        &self,
+        script: &str,
+    ) -> Result<T, Box<EvalAltResult>> {
         self.eval_expression_with_scope(&mut Scope::new(), script)
     }
 
@@ -701,7 +703,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Scope};
     ///
     /// let engine = Engine::new();
@@ -718,7 +720,7 @@ impl Engine {
         &self,
         scope: &mut Scope,
         script: &str,
-    ) -> Result<T, EvalAltResult> {
+    ) -> Result<T, Box<EvalAltResult>> {
         let scripts = [script];
         let stream = lex(&scripts);
         // Since the AST will be thrown away afterwards, don't bother to optimize it
@@ -731,7 +733,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::Engine;
     ///
     /// let engine = Engine::new();
@@ -744,7 +746,7 @@ impl Engine {
     /// # Ok(())
     /// # }
     /// ```
-    pub fn eval_ast<T: Variant + Clone>(&self, ast: &AST) -> Result<T, EvalAltResult> {
+    pub fn eval_ast<T: Variant + Clone>(&self, ast: &AST) -> Result<T, Box<EvalAltResult>> {
         self.eval_ast_with_scope(&mut Scope::new(), ast)
     }
 
@@ -753,7 +755,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Scope};
     ///
     /// let engine = Engine::new();
@@ -781,15 +783,16 @@ impl Engine {
         &self,
         scope: &mut Scope,
         ast: &AST,
-    ) -> Result<T, EvalAltResult> {
-        let result = self
-            .eval_ast_with_scope_raw(scope, ast)
-            .map_err(|err| *err)?;
+    ) -> Result<T, Box<EvalAltResult>> {
+        let result = self.eval_ast_with_scope_raw(scope, ast)?;
 
         let return_type = self.map_type_name(result.type_name());
 
         return result.try_cast::<T>().ok_or_else(|| {
-            EvalAltResult::ErrorMismatchOutputType(return_type.to_string(), Position::none())
+            Box::new(EvalAltResult::ErrorMismatchOutputType(
+                return_type.to_string(),
+                Position::none(),
+            ))
         });
     }
 
@@ -812,7 +815,7 @@ impl Engine {
     /// Evaluate a file, but throw away the result and only return error (if any).
     /// Useful for when you don't need the result, but still need to keep track of possible errors.
     #[cfg(not(feature = "no_std"))]
-    pub fn consume_file(&self, path: PathBuf) -> Result<(), EvalAltResult> {
+    pub fn consume_file(&self, path: PathBuf) -> Result<(), Box<EvalAltResult>> {
         Self::read_file(path).and_then(|contents| self.consume(&contents))
     }
 
@@ -823,19 +826,23 @@ impl Engine {
         &self,
         scope: &mut Scope,
         path: PathBuf,
-    ) -> Result<(), EvalAltResult> {
+    ) -> Result<(), Box<EvalAltResult>> {
         Self::read_file(path).and_then(|contents| self.consume_with_scope(scope, &contents))
     }
 
     /// Evaluate a string, but throw away the result and only return error (if any).
     /// Useful for when you don't need the result, but still need to keep track of possible errors.
-    pub fn consume(&self, script: &str) -> Result<(), EvalAltResult> {
+    pub fn consume(&self, script: &str) -> Result<(), Box<EvalAltResult>> {
         self.consume_with_scope(&mut Scope::new(), script)
     }
 
     /// Evaluate a string with own scope, but throw away the result and only return error (if any).
     /// Useful for when you don't need the result, but still need to keep track of possible errors.
-    pub fn consume_with_scope(&self, scope: &mut Scope, script: &str) -> Result<(), EvalAltResult> {
+    pub fn consume_with_scope(
+        &self,
+        scope: &mut Scope,
+        script: &str,
+    ) -> Result<(), Box<EvalAltResult>> {
         let scripts = [script];
         let stream = lex(&scripts);
 
@@ -846,7 +853,7 @@ impl Engine {
 
     /// Evaluate an AST, but throw away the result and only return error (if any).
     /// Useful for when you don't need the result, but still need to keep track of possible errors.
-    pub fn consume_ast(&self, ast: &AST) -> Result<(), EvalAltResult> {
+    pub fn consume_ast(&self, ast: &AST) -> Result<(), Box<EvalAltResult>> {
         self.consume_ast_with_scope(&mut Scope::new(), ast)
     }
 
@@ -856,7 +863,7 @@ impl Engine {
         &self,
         scope: &mut Scope,
         ast: &AST,
-    ) -> Result<(), EvalAltResult> {
+    ) -> Result<(), Box<EvalAltResult>> {
         ast.0
             .iter()
             .try_fold(Dynamic::from_unit(), |_, stmt| {
@@ -865,7 +872,7 @@ impl Engine {
             .map_or_else(
                 |err| match *err {
                     EvalAltResult::Return(_, _) => Ok(()),
-                    err => Err(err),
+                    err => Err(Box::new(err)),
                 },
                 |_| Ok(()),
             )
@@ -876,7 +883,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # #[cfg(not(feature = "no_function"))]
     /// # {
     /// use rhai::{Engine, Scope};
@@ -913,21 +920,22 @@ impl Engine {
         ast: &AST,
         name: &str,
         args: A,
-    ) -> Result<T, EvalAltResult> {
+    ) -> Result<T, Box<EvalAltResult>> {
         let mut arg_values = args.into_vec();
         let mut args: Vec<_> = arg_values.iter_mut().collect();
         let fn_lib = Some(ast.1.as_ref());
         let pos = Position::none();
 
-        let result = self
-            .call_fn_raw(Some(scope), fn_lib, name, &mut args, None, pos, 0)
-            .map_err(|err| *err)?;
+        let result = self.call_fn_raw(Some(scope), fn_lib, name, &mut args, None, pos, 0)?;
 
         let return_type = self.map_type_name(result.type_name());
 
-        return result
-            .try_cast()
-            .ok_or_else(|| EvalAltResult::ErrorMismatchOutputType(return_type.into(), pos));
+        return result.try_cast().ok_or_else(|| {
+            Box::new(EvalAltResult::ErrorMismatchOutputType(
+                return_type.into(),
+                pos,
+            ))
+        });
     }
 
     /// Optimize the `AST` with constants defined in an external Scope.
@@ -961,7 +969,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # use std::sync::RwLock;
     /// # use std::sync::Arc;
     /// use rhai::Engine;
@@ -989,7 +997,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # use std::sync::RwLock;
     /// # use std::sync::Arc;
     /// use rhai::Engine;
@@ -1046,7 +1054,7 @@ impl Engine {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # use std::sync::RwLock;
     /// # use std::sync::Arc;
     /// use rhai::Engine;
diff --git a/src/engine.rs b/src/engine.rs
index 340dd7d9..d846c2d7 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -205,7 +205,7 @@ impl DerefMut for FunctionsLib {
 /// Rhai main scripting engine.
 ///
 /// ```
-/// # fn main() -> Result<(), rhai::EvalAltResult> {
+/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
 /// use rhai::Engine;
 ///
 /// let engine = Engine::new();
@@ -1383,13 +1383,11 @@ impl Engine {
 
                         // Compile the script text
                         // No optimizations because we only run it once
-                        let mut ast = self
-                            .compile_with_scope_and_optimization_level(
-                                &Scope::new(),
-                                script,
-                                OptimizationLevel::None,
-                            )
-                            .map_err(|err| EvalAltResult::ErrorParsing(Box::new(err)))?;
+                        let mut ast = self.compile_with_scope_and_optimization_level(
+                            &Scope::new(),
+                            script,
+                            OptimizationLevel::None,
+                        )?;
 
                         // If new functions are defined within the eval string, it is an error
                         if ast.1.len() > 0 {
diff --git a/src/fn_func.rs b/src/fn_func.rs
index 4c3544de..b9add7e4 100644
--- a/src/fn_func.rs
+++ b/src/fn_func.rs
@@ -21,18 +21,18 @@ pub trait Func<ARGS, RET> {
     /// # Examples
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Func};                       // use 'Func' for 'create_from_ast'
     ///
     /// let engine = Engine::new();                     // create a new 'Engine' just for this
     ///
-    /// let ast = engine.compile("fn calc(x, y) { x + y.len() < 42 }")?;
+    /// let ast = engine.compile("fn calc(x, y) { x + len(y) < 42 }")?;
     ///
     /// // Func takes two type parameters:
     /// //   1) a tuple made up of the types of the script function's parameters
     /// //   2) the return type of the script function
     /// //
-    /// // 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, EvalAltResult>> and is callable!
+    /// // 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, Box<EvalAltResult>>> and is callable!
     /// let func = Func::<(i64, String), bool>::create_from_ast(
     /// //                ^^^^^^^^^^^^^ function parameter types in tuple
     ///
@@ -52,18 +52,18 @@ pub trait Func<ARGS, RET> {
     /// # Examples
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Func};                       // use 'Func' for 'create_from_script'
     ///
     /// let engine = Engine::new();                     // create a new 'Engine' just for this
     ///
-    /// let script = "fn calc(x, y) { x + y.len() < 42 }";
+    /// let script = "fn calc(x, y) { x + len(y) < 42 }";
     ///
     /// // Func takes two type parameters:
     /// //   1) a tuple made up of the types of the script function's parameters
     /// //   2) the return type of the script function
     /// //
-    /// // 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, EvalAltResult>> and is callable!
+    /// // 'func' will have type Box<dyn Fn(i64, String) -> Result<bool, Box<EvalAltResult>>> and is callable!
     /// let func = Func::<(i64, String), bool>::create_from_script(
     /// //                ^^^^^^^^^^^^^ function parameter types in tuple
     ///
@@ -80,7 +80,7 @@ pub trait Func<ARGS, RET> {
         self,
         script: &str,
         entry_point: &str,
-    ) -> Result<Self::Output, ParseError>;
+    ) -> Result<Self::Output, Box<ParseError>>;
 }
 
 macro_rules! def_anonymous_fn {
@@ -91,10 +91,10 @@ macro_rules! def_anonymous_fn {
         impl<$($par: Variant + Clone,)* RET: Variant + Clone> Func<($($par,)*), RET> for Engine
         {
             #[cfg(feature = "sync")]
-            type Output = Box<dyn Fn($($par),*) -> Result<RET, EvalAltResult> + Send + Sync>;
+            type Output = Box<dyn Fn($($par),*) -> Result<RET, Box<EvalAltResult>> + Send + Sync>;
 
             #[cfg(not(feature = "sync"))]
-            type Output = Box<dyn Fn($($par),*) -> Result<RET, EvalAltResult>>;
+            type Output = Box<dyn Fn($($par),*) -> Result<RET, Box<EvalAltResult>>>;
 
             fn create_from_ast(self, ast: AST, entry_point: &str) -> Self::Output {
                 let name = entry_point.to_string();
@@ -104,7 +104,7 @@ macro_rules! def_anonymous_fn {
                 })
             }
 
-            fn create_from_script(self, script: &str, entry_point: &str) -> Result<Self::Output, ParseError> {
+            fn create_from_script(self, script: &str, entry_point: &str) -> Result<Self::Output, Box<ParseError>> {
                 let ast = self.compile(script)?;
                 Ok(Func::<($($par,)*), RET>::create_from_ast(self, ast, entry_point))
             }
diff --git a/src/fn_register.rs b/src/fn_register.rs
index 393bda5a..4e490b67 100644
--- a/src/fn_register.rs
+++ b/src/fn_register.rs
@@ -16,7 +16,7 @@ pub trait RegisterFn<FN, ARGS, RET> {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, RegisterFn};
     ///
     /// // Normal function
@@ -48,7 +48,7 @@ pub trait RegisterDynamicFn<FN, ARGS> {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// use rhai::{Engine, Dynamic, RegisterDynamicFn};
     ///
     /// // Function that returns a Dynamic value
@@ -68,7 +68,7 @@ pub trait RegisterDynamicFn<FN, ARGS> {
     fn register_dynamic_fn(&mut self, name: &str, f: FN);
 }
 
-/// A trait to register fallible custom functions returning Result<_, EvalAltResult> with the `Engine`.
+/// A trait to register fallible custom functions returning `Result<_, Box<EvalAltResult>>` with the `Engine`.
 pub trait RegisterResultFn<FN, ARGS, RET> {
     /// Register a custom fallible function with the `Engine`.
     ///
@@ -78,9 +78,9 @@ pub trait RegisterResultFn<FN, ARGS, RET> {
     /// use rhai::{Engine, RegisterResultFn, EvalAltResult};
     ///
     /// // Normal function
-    /// fn div(x: i64, y: i64) -> Result<i64, EvalAltResult> {
+    /// fn div(x: i64, y: i64) -> Result<i64, Box<EvalAltResult>> {
     ///     if y == 0 {
-    ///         // '.into()' automatically converts to 'EvalAltResult::ErrorRuntime'
+    ///         // '.into()' automatically converts to 'Box<EvalAltResult::ErrorRuntime>'
     ///         Err("division by zero!".into())
     ///     } else {
     ///         Ok(x / y)
@@ -180,10 +180,10 @@ pub fn map_identity(data: Dynamic, _pos: Position) -> Result<Dynamic, Box<EvalAl
     Ok(data)
 }
 
-/// To Result<Dynamic, EvalAltResult> mapping function.
+/// To `Result<Dynamic, Box<EvalAltResult>>` mapping function.
 #[inline]
 pub fn map_result<T: Variant + Clone>(
-    data: Result<T, EvalAltResult>,
+    data: Result<T, Box<EvalAltResult>>,
     pos: Position,
 ) -> Result<Dynamic, Box<EvalAltResult>> {
     data.map(|v| v.into_dynamic())
@@ -241,9 +241,9 @@ macro_rules! def_register {
             $($par: Variant + Clone,)*
 
             #[cfg(feature = "sync")]
-            FN: Fn($($param),*) -> Result<RET, EvalAltResult> + Send + Sync + 'static,
+            FN: Fn($($param),*) -> Result<RET, Box<EvalAltResult>> + Send + Sync + 'static,
             #[cfg(not(feature = "sync"))]
-            FN: Fn($($param),*) -> Result<RET, EvalAltResult> + 'static,
+            FN: Fn($($param),*) -> Result<RET, Box<EvalAltResult>> + 'static,
 
             RET: Variant + Clone
         > RegisterResultFn<FN, ($($mark,)*), RET> for Engine
diff --git a/src/lib.rs b/src/lib.rs
index 3729e1f4..f7fd783c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -23,7 +23,7 @@
 //! ```,no_run
 //! use rhai::{Engine, EvalAltResult, RegisterFn};
 //!
-//! fn main() -> Result<(), EvalAltResult>
+//! fn main() -> Result<(), Box<EvalAltResult>>
 //! {
 //!     // Define external function
 //!     fn compute_something(x: i64) -> bool {
@@ -71,7 +71,7 @@ extern crate alloc;
 
 mod any;
 mod api;
-mod builtin;
+//mod builtin;
 mod engine;
 mod error;
 mod fn_call;
diff --git a/src/packages/arithmetic.rs b/src/packages/arithmetic.rs
index 24bf9687..3ccbf5e7 100644
--- a/src/packages/arithmetic.rs
+++ b/src/packages/arithmetic.rs
@@ -22,67 +22,73 @@ use crate::stdlib::{
 };
 
 // Checked add
-fn add<T: Display + CheckedAdd>(x: T, y: T) -> Result<T, EvalAltResult> {
+fn add<T: Display + CheckedAdd>(x: T, y: T) -> Result<T, Box<EvalAltResult>> {
     x.checked_add(&y).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Addition overflow: {} + {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Checked subtract
-fn sub<T: Display + CheckedSub>(x: T, y: T) -> Result<T, EvalAltResult> {
+fn sub<T: Display + CheckedSub>(x: T, y: T) -> Result<T, Box<EvalAltResult>> {
     x.checked_sub(&y).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Subtraction underflow: {} - {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Checked multiply
-fn mul<T: Display + CheckedMul>(x: T, y: T) -> Result<T, EvalAltResult> {
+fn mul<T: Display + CheckedMul>(x: T, y: T) -> Result<T, Box<EvalAltResult>> {
     x.checked_mul(&y).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Multiplication overflow: {} * {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Checked divide
-fn div<T>(x: T, y: T) -> Result<T, EvalAltResult>
+fn div<T>(x: T, y: T) -> Result<T, Box<EvalAltResult>>
 where
     T: Display + CheckedDiv + PartialEq + Zero,
 {
     // Detect division by zero
     if y == T::zero() {
-        return Err(EvalAltResult::ErrorArithmetic(
+        return Err(Box::new(EvalAltResult::ErrorArithmetic(
             format!("Division by zero: {} / {}", x, y),
             Position::none(),
-        ));
+        )));
     }
 
     x.checked_div(&y).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Division overflow: {} / {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Checked negative - e.g. -(i32::MIN) will overflow i32::MAX
-fn neg<T: Display + CheckedNeg>(x: T) -> Result<T, EvalAltResult> {
+fn neg<T: Display + CheckedNeg>(x: T) -> Result<T, Box<EvalAltResult>> {
     x.checked_neg().ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(format!("Negation overflow: -{}", x), Position::none())
+        Box::new(EvalAltResult::ErrorArithmetic(
+            format!("Negation overflow: -{}", x),
+            Position::none(),
+        ))
     })
 }
 // Checked absolute
-fn abs<T: Display + CheckedNeg + PartialOrd + Zero>(x: T) -> Result<T, EvalAltResult> {
+fn abs<T: Display + CheckedNeg + PartialOrd + Zero>(x: T) -> Result<T, Box<EvalAltResult>> {
     // FIX - We don't use Signed::abs() here because, contrary to documentation, it panics
     //       when the number is ::MIN instead of returning ::MIN itself.
     if x >= <T as Zero>::zero() {
         Ok(x)
     } else {
         x.checked_neg().ok_or_else(|| {
-            EvalAltResult::ErrorArithmetic(format!("Negation overflow: -{}", x), Position::none())
+            Box::new(EvalAltResult::ErrorArithmetic(
+                format!("Negation overflow: -{}", x),
+                Position::none(),
+            ))
         })
     }
 }
@@ -129,37 +135,37 @@ fn binary_xor<T: BitXor>(x: T, y: T) -> <T as BitXor>::Output {
     x ^ y
 }
 // Checked left-shift
-fn shl<T: Display + CheckedShl>(x: T, y: INT) -> Result<T, EvalAltResult> {
+fn shl<T: Display + CheckedShl>(x: T, y: INT) -> Result<T, Box<EvalAltResult>> {
     // Cannot shift by a negative number of bits
     if y < 0 {
-        return Err(EvalAltResult::ErrorArithmetic(
+        return Err(Box::new(EvalAltResult::ErrorArithmetic(
             format!("Left-shift by a negative number: {} << {}", x, y),
             Position::none(),
-        ));
+        )));
     }
 
     CheckedShl::checked_shl(&x, y as u32).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Left-shift by too many bits: {} << {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Checked right-shift
-fn shr<T: Display + CheckedShr>(x: T, y: INT) -> Result<T, EvalAltResult> {
+fn shr<T: Display + CheckedShr>(x: T, y: INT) -> Result<T, Box<EvalAltResult>> {
     // Cannot shift by a negative number of bits
     if y < 0 {
-        return Err(EvalAltResult::ErrorArithmetic(
+        return Err(Box::new(EvalAltResult::ErrorArithmetic(
             format!("Right-shift by a negative number: {} >> {}", x, y),
             Position::none(),
-        ));
+        )));
     }
 
     CheckedShr::checked_shr(&x, y as u32).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Right-shift by too many bits: {} % {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Unchecked left-shift - may panic if shifting by a negative number of bits
@@ -171,12 +177,12 @@ fn shr_u<T: Shr<T>>(x: T, y: T) -> <T as Shr<T>>::Output {
     x.shr(y)
 }
 // Checked modulo
-fn modulo<T: Display + CheckedRem>(x: T, y: T) -> Result<T, EvalAltResult> {
+fn modulo<T: Display + CheckedRem>(x: T, y: T) -> Result<T, Box<EvalAltResult>> {
     x.checked_rem(&y).ok_or_else(|| {
-        EvalAltResult::ErrorArithmetic(
+        Box::new(EvalAltResult::ErrorArithmetic(
             format!("Modulo division by zero or overflow: {} % {}", x, y),
             Position::none(),
-        )
+        ))
     })
 }
 // Unchecked modulo - may panic if dividing by zero
@@ -184,25 +190,25 @@ fn modulo_u<T: Rem>(x: T, y: T) -> <T as Rem>::Output {
     x % y
 }
 // Checked power
-fn pow_i_i(x: INT, y: INT) -> Result<INT, EvalAltResult> {
+fn pow_i_i(x: INT, y: INT) -> Result<INT, Box<EvalAltResult>> {
     #[cfg(not(feature = "only_i32"))]
     {
         if y > (u32::MAX as INT) {
-            Err(EvalAltResult::ErrorArithmetic(
+            Err(Box::new(EvalAltResult::ErrorArithmetic(
                 format!("Integer raised to too large an index: {} ~ {}", x, y),
                 Position::none(),
-            ))
+            )))
         } else if y < 0 {
-            Err(EvalAltResult::ErrorArithmetic(
+            Err(Box::new(EvalAltResult::ErrorArithmetic(
                 format!("Integer raised to a negative index: {} ~ {}", x, y),
                 Position::none(),
-            ))
+            )))
         } else {
             x.checked_pow(y as u32).ok_or_else(|| {
-                EvalAltResult::ErrorArithmetic(
+                Box::new(EvalAltResult::ErrorArithmetic(
                     format!("Power overflow: {} ~ {}", x, y),
                     Position::none(),
-                )
+                ))
             })
         }
     }
@@ -210,16 +216,16 @@ fn pow_i_i(x: INT, y: INT) -> Result<INT, EvalAltResult> {
     #[cfg(feature = "only_i32")]
     {
         if y < 0 {
-            Err(EvalAltResult::ErrorArithmetic(
+            Err(Box::new(EvalAltResult::ErrorArithmetic(
                 format!("Integer raised to a negative index: {} ~ {}", x, y),
                 Position::none(),
-            ))
+            )))
         } else {
             x.checked_pow(y as u32).ok_or_else(|| {
-                EvalAltResult::ErrorArithmetic(
+                Box::new(EvalAltResult::ErrorArithmetic(
                     format!("Power overflow: {} ~ {}", x, y),
                     Position::none(),
-                )
+                ))
             })
         }
     }
@@ -235,13 +241,13 @@ fn pow_f_f(x: FLOAT, y: FLOAT) -> FLOAT {
 }
 // Checked power
 #[cfg(not(feature = "no_float"))]
-fn pow_f_i(x: FLOAT, y: INT) -> Result<FLOAT, EvalAltResult> {
+fn pow_f_i(x: FLOAT, y: INT) -> Result<FLOAT, Box<EvalAltResult>> {
     // Raise to power that is larger than an i32
     if y > (i32::MAX as INT) {
-        return Err(EvalAltResult::ErrorArithmetic(
+        return Err(Box::new(EvalAltResult::ErrorArithmetic(
             format!("Number raised to too large an index: {} ~ {}", x, y),
             Position::none(),
-        ));
+        )));
     }
 
     Ok(x.powi(y as i32))
diff --git a/src/packages/array_basic.rs b/src/packages/array_basic.rs
index e6b3fd1a..2c4c342c 100644
--- a/src/packages/array_basic.rs
+++ b/src/packages/array_basic.rs
@@ -1,7 +1,7 @@
 use super::{reg_binary, reg_binary_mut, reg_trinary_mut, reg_unary_mut};
 
-use crate::def_package;
 use crate::any::{Dynamic, Variant};
+use crate::def_package;
 use crate::engine::Array;
 use crate::fn_register::{map_dynamic as map, map_identity as pass};
 use crate::parser::INT;
diff --git a/src/packages/iter_basic.rs b/src/packages/iter_basic.rs
index eefc9e0f..830193eb 100644
--- a/src/packages/iter_basic.rs
+++ b/src/packages/iter_basic.rs
@@ -1,7 +1,7 @@
 use super::{reg_binary, reg_trinary, reg_unary_mut, PackageStore};
 
-use crate::def_package;
 use crate::any::{Dynamic, Union, Variant};
+use crate::def_package;
 use crate::engine::{Array, Map};
 use crate::fn_register::map_dynamic as map;
 use crate::parser::INT;
diff --git a/src/packages/map_basic.rs b/src/packages/map_basic.rs
index b1fb3706..72f6a698 100644
--- a/src/packages/map_basic.rs
+++ b/src/packages/map_basic.rs
@@ -1,7 +1,7 @@
 use super::{reg_binary, reg_binary_mut, reg_unary_mut};
 
-use crate::def_package;
 use crate::any::Dynamic;
+use crate::def_package;
 use crate::engine::Map;
 use crate::fn_register::map_dynamic as map;
 use crate::parser::INT;
diff --git a/src/packages/math_basic.rs b/src/packages/math_basic.rs
index eee708c9..72b953c0 100644
--- a/src/packages/math_basic.rs
+++ b/src/packages/math_basic.rs
@@ -95,10 +95,10 @@ def_package!(BasicMathPackage:"Basic mathematic functions.", lib, {
                 "to_int",
                 |x: f32| {
                     if x > (MAX_INT as f32) {
-                        return Err(EvalAltResult::ErrorArithmetic(
+                        return Err(Box::new(EvalAltResult::ErrorArithmetic(
                             format!("Integer overflow: to_int({})", x),
                             Position::none(),
-                        ));
+                        )));
                     }
 
                     Ok(x.trunc() as INT)
@@ -110,10 +110,10 @@ def_package!(BasicMathPackage:"Basic mathematic functions.", lib, {
                 "to_int",
                 |x: FLOAT| {
                     if x > (MAX_INT as FLOAT) {
-                        return Err(EvalAltResult::ErrorArithmetic(
+                        return Err(Box::new(EvalAltResult::ErrorArithmetic(
                             format!("Integer overflow: to_int({})", x),
                             Position::none(),
-                        ));
+                        )));
                     }
 
                     Ok(x.trunc() as INT)
diff --git a/src/packages/mod.rs b/src/packages/mod.rs
index 25318d23..611dfef8 100644
--- a/src/packages/mod.rs
+++ b/src/packages/mod.rs
@@ -18,9 +18,11 @@ mod time_basic;
 mod utils;
 
 pub use arithmetic::ArithmeticPackage;
+#[cfg(not(feature = "no_index"))]
 pub use array_basic::BasicArrayPackage;
 pub use iter_basic::BasicIteratorPackage;
 pub use logic::LogicPackage;
+#[cfg(not(feature = "no_object"))]
 pub use map_basic::BasicMapPackage;
 pub use math_basic::BasicMathPackage;
 pub use pkg_core::CorePackage;
diff --git a/src/packages/pkg_std.rs b/src/packages/pkg_std.rs
index f17c275e..51aa9dc0 100644
--- a/src/packages/pkg_std.rs
+++ b/src/packages/pkg_std.rs
@@ -1,4 +1,6 @@
+#[cfg(not(feature = "no_index"))]
 use super::array_basic::BasicArrayPackage;
+#[cfg(not(feature = "no_object"))]
 use super::map_basic::BasicMapPackage;
 use super::math_basic::BasicMathPackage;
 use super::pkg_core::CorePackage;
diff --git a/src/packages/time_basic.rs b/src/packages/time_basic.rs
index 91d5c9bc..13faad95 100644
--- a/src/packages/time_basic.rs
+++ b/src/packages/time_basic.rs
@@ -31,13 +31,13 @@ def_package!(BasicTimePackage:"Basic timing utilities.", lib, {
                         #[cfg(not(feature = "unchecked"))]
                         {
                             if seconds > (MAX_INT as u64) {
-                                return Err(EvalAltResult::ErrorArithmetic(
+                                return Err(Box::new(EvalAltResult::ErrorArithmetic(
                                     format!(
                                         "Integer overflow for timestamp duration: {}",
                                         -(seconds as i64)
                                     ),
                                     Position::none(),
-                                ));
+                                )));
                             }
                         }
                         return Ok(-(seconds as INT));
@@ -53,10 +53,10 @@ def_package!(BasicTimePackage:"Basic timing utilities.", lib, {
                         #[cfg(not(feature = "unchecked"))]
                         {
                             if seconds > (MAX_INT as u64) {
-                                return Err(EvalAltResult::ErrorArithmetic(
+                                return Err(Box::new(EvalAltResult::ErrorArithmetic(
                                     format!("Integer overflow for timestamp duration: {}", seconds),
                                     Position::none(),
-                                ));
+                                )));
                             }
                         }
                         return Ok(seconds as INT);
diff --git a/src/parser.rs b/src/parser.rs
index c77262a9..ea7b9a3c 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -72,7 +72,7 @@ impl AST {
     /// # Example
     ///
     /// ```
-    /// # fn main() -> Result<(), rhai::EvalAltResult> {
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
     /// # #[cfg(not(feature = "no_function"))]
     /// # {
     /// use rhai::Engine;
diff --git a/src/result.rs b/src/result.rs
index 21fe7ef8..4a4cb6bc 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -228,20 +228,23 @@ impl fmt::Display for EvalAltResult {
     }
 }
 
-impl From<ParseError> for EvalAltResult {
+impl From<ParseError> for Box<EvalAltResult> {
     fn from(err: ParseError) -> Self {
-        Self::ErrorParsing(Box::new(err))
+        Box::new(EvalAltResult::ErrorParsing(Box::new(err)))
     }
 }
-impl From<Box<ParseError>> for EvalAltResult {
+impl From<Box<ParseError>> for Box<EvalAltResult> {
     fn from(err: Box<ParseError>) -> Self {
-        Self::ErrorParsing(err)
+        Box::new(EvalAltResult::ErrorParsing(err))
     }
 }
 
-impl<T: AsRef<str>> From<T> for EvalAltResult {
+impl<T: AsRef<str>> From<T> for Box<EvalAltResult> {
     fn from(err: T) -> Self {
-        Self::ErrorRuntime(err.as_ref().to_string(), Position::none())
+        Box::new(EvalAltResult::ErrorRuntime(
+            err.as_ref().to_string(),
+            Position::none(),
+        ))
     }
 }
 
diff --git a/src/scope.rs b/src/scope.rs
index a9fd579c..6abfb40f 100644
--- a/src/scope.rs
+++ b/src/scope.rs
@@ -42,7 +42,7 @@ pub(crate) struct EntryRef<'a> {
 /// # Example
 ///
 /// ```
-/// # fn main() -> Result<(), rhai::EvalAltResult> {
+/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
 /// use rhai::{Engine, Scope};
 ///
 /// let engine = Engine::new();
diff --git a/tests/arrays.rs b/tests/arrays.rs
index a41f0a63..60a41be4 100644
--- a/tests/arrays.rs
+++ b/tests/arrays.rs
@@ -2,7 +2,7 @@
 use rhai::{Array, Engine, EvalAltResult, RegisterFn, INT};
 
 #[test]
-fn test_arrays() -> Result<(), EvalAltResult> {
+fn test_arrays() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = [1, 2, 3]; x[1]")?, 2);
@@ -58,7 +58,7 @@ fn test_arrays() -> Result<(), EvalAltResult> {
 
 #[test]
 #[cfg(not(feature = "no_object"))]
-fn test_array_with_structs() -> Result<(), EvalAltResult> {
+fn test_array_with_structs() -> Result<(), Box<EvalAltResult>> {
     #[derive(Clone)]
     struct TestStruct {
         x: INT,
diff --git a/tests/binary_ops.rs b/tests/binary_ops.rs
index 922c6a43..7ede89fb 100644
--- a/tests/binary_ops.rs
+++ b/tests/binary_ops.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_binary_ops() -> Result<(), EvalAltResult> {
+fn test_binary_ops() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("10 % 4")?, 2);
diff --git a/tests/bit_shift.rs b/tests/bit_shift.rs
index e8e360f3..0b888e32 100644
--- a/tests/bit_shift.rs
+++ b/tests/bit_shift.rs
@@ -1,14 +1,14 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_left_shift() -> Result<(), EvalAltResult> {
+fn test_left_shift() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("4 << 2")?, 16);
     Ok(())
 }
 
 #[test]
-fn test_right_shift() -> Result<(), EvalAltResult> {
+fn test_right_shift() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("9 >> 1")?, 4);
     Ok(())
diff --git a/tests/bool_op.rs b/tests/bool_op.rs
index 3bd5859a..913106e6 100644
--- a/tests/bool_op.rs
+++ b/tests/bool_op.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult};
 
 #[test]
-fn test_bool_op1() -> Result<(), EvalAltResult> {
+fn test_bool_op1() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<bool>("true && (false || true)")?, true);
@@ -11,7 +11,7 @@ fn test_bool_op1() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_bool_op2() -> Result<(), EvalAltResult> {
+fn test_bool_op2() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<bool>("false && (false || true)")?, false);
@@ -21,7 +21,7 @@ fn test_bool_op2() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_bool_op3() -> Result<(), EvalAltResult> {
+fn test_bool_op3() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert!(engine.eval::<bool>("true && (false || 123)").is_err());
@@ -33,7 +33,7 @@ fn test_bool_op3() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_bool_op_short_circuit() -> Result<(), EvalAltResult> {
+fn test_bool_op_short_circuit() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/call_fn.rs b/tests/call_fn.rs
index fc658a15..f3d2a689 100644
--- a/tests/call_fn.rs
+++ b/tests/call_fn.rs
@@ -2,7 +2,7 @@
 use rhai::{Engine, EvalAltResult, Func, ParseErrorType, Scope, INT};
 
 #[test]
-fn test_fn() -> Result<(), EvalAltResult> {
+fn test_fn() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     // Expect duplicated parameters error
@@ -19,7 +19,7 @@ fn test_fn() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_call_fn() -> Result<(), EvalAltResult> {
+fn test_call_fn() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     let mut scope = Scope::new();
 
@@ -61,7 +61,7 @@ fn test_call_fn() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_anonymous_fn() -> Result<(), EvalAltResult> {
+fn test_anonymous_fn() -> Result<(), Box<EvalAltResult>> {
     let calc_func = Func::<(INT, INT, INT), INT>::create_from_script(
         Engine::new(),
         "fn calc(x, y, z) { (x + y) * z }",
diff --git a/tests/chars.rs b/tests/chars.rs
index db13f840..6882633a 100644
--- a/tests/chars.rs
+++ b/tests/chars.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult};
 
 #[test]
-fn test_chars() -> Result<(), EvalAltResult> {
+fn test_chars() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<char>("'y'")?, 'y');
diff --git a/tests/compound_equality.rs b/tests/compound_equality.rs
index b516bb97..b09115a0 100644
--- a/tests/compound_equality.rs
+++ b/tests/compound_equality.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_or_equals() -> Result<(), EvalAltResult> {
+fn test_or_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 16; x |= 74; x")?, 90);
@@ -12,7 +12,7 @@ fn test_or_equals() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_and_equals() -> Result<(), EvalAltResult> {
+fn test_and_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 16; x &= 31; x")?, 16);
@@ -24,42 +24,42 @@ fn test_and_equals() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_xor_equals() -> Result<(), EvalAltResult> {
+fn test_xor_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 90; x ^= 12; x")?, 86);
     Ok(())
 }
 
 #[test]
-fn test_multiply_equals() -> Result<(), EvalAltResult> {
+fn test_multiply_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 2; x *= 3; x")?, 6);
     Ok(())
 }
 
 #[test]
-fn test_divide_equals() -> Result<(), EvalAltResult> {
+fn test_divide_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 6; x /= 2; x")?, 3);
     Ok(())
 }
 
 #[test]
-fn test_left_shift_equals() -> Result<(), EvalAltResult> {
+fn test_left_shift_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 9; x >>=1; x")?, 4);
     Ok(())
 }
 
 #[test]
-fn test_right_shift_equals() -> Result<(), EvalAltResult> {
+fn test_right_shift_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 4; x<<= 2; x")?, 16);
     Ok(())
 }
 
 #[test]
-fn test_modulo_equals() -> Result<(), EvalAltResult> {
+fn test_modulo_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<INT>("let x = 10; x %= 4; x")?, 2);
     Ok(())
diff --git a/tests/constants.rs b/tests/constants.rs
index 2dd62000..55752d28 100644
--- a/tests/constants.rs
+++ b/tests/constants.rs
@@ -1,21 +1,21 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_constant() -> Result<(), EvalAltResult> {
+fn test_constant() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("const x = 123; x")?, 123);
 
-    assert!(
-        matches!(engine.eval::<INT>("const x = 123; x = 42;").expect_err("expects error"),
-        EvalAltResult::ErrorAssignmentToConstant(var, _) if var == "x")
-    );
+    assert!(matches!(
+        *engine.eval::<INT>("const x = 123; x = 42;").expect_err("expects error"),
+        EvalAltResult::ErrorAssignmentToConstant(var, _) if var == "x"
+    ));
 
     #[cfg(not(feature = "no_index"))]
-    assert!(
-        matches!(engine.eval::<INT>("const x = [1, 2, 3, 4, 5]; x[2] = 42;").expect_err("expects error"),
-        EvalAltResult::ErrorAssignmentToConstant(var, _) if var == "x")
-    );
+    assert!(matches!(
+        *engine.eval::<INT>("const x = [1, 2, 3, 4, 5]; x[2] = 42;").expect_err("expects error"),
+        EvalAltResult::ErrorAssignmentToConstant(var, _) if var == "x"
+    ));
 
     Ok(())
 }
diff --git a/tests/decrement.rs b/tests/decrement.rs
index a8cb2634..ab1f9376 100644
--- a/tests/decrement.rs
+++ b/tests/decrement.rs
@@ -1,14 +1,15 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_decrement() -> Result<(), EvalAltResult> {
+fn test_decrement() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 10; x -= 7; x")?, 3);
 
-    assert!(matches!(engine
-            .eval::<String>(r#"let s = "test"; s -= "ing"; s"#)
-            .expect_err("expects error"), EvalAltResult::ErrorFunctionNotFound(err, _) if err == "- (string, string)"));
+    assert!(matches!(
+        *engine.eval::<String>(r#"let s = "test"; s -= "ing"; s"#).expect_err("expects error"),
+        EvalAltResult::ErrorFunctionNotFound(err, _) if err == "- (string, string)"
+    ));
 
     Ok(())
 }
diff --git a/tests/eval.rs b/tests/eval.rs
index bf6f750f..c9027a25 100644
--- a/tests/eval.rs
+++ b/tests/eval.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, Scope, INT};
 
 #[test]
-fn test_eval() -> Result<(), EvalAltResult> {
+fn test_eval() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -18,7 +18,7 @@ fn test_eval() -> Result<(), EvalAltResult> {
 
 #[test]
 #[cfg(not(feature = "no_function"))]
-fn test_eval_function() -> Result<(), EvalAltResult> {
+fn test_eval_function() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     let mut scope = Scope::new();
 
@@ -61,7 +61,7 @@ fn test_eval_function() -> Result<(), EvalAltResult> {
 
 #[test]
 #[cfg(not(feature = "no_function"))]
-fn test_eval_override() -> Result<(), EvalAltResult> {
+fn test_eval_override() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/expressions.rs b/tests/expressions.rs
index 2091fe4e..35a6b90c 100644
--- a/tests/expressions.rs
+++ b/tests/expressions.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, Scope, INT};
 
 #[test]
-fn test_expressions() -> Result<(), EvalAltResult> {
+fn test_expressions() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     let mut scope = Scope::new();
 
@@ -28,7 +28,7 @@ fn test_expressions() -> Result<(), EvalAltResult> {
 /// This example taken from https://github.com/jonathandturner/rhai/issues/115
 #[test]
 #[cfg(not(feature = "no_object"))]
-fn test_expressions_eval() -> Result<(), EvalAltResult> {
+fn test_expressions_eval() -> Result<(), Box<EvalAltResult>> {
     #[derive(Debug, Clone)]
     struct AGENT {
         pub gender: String,
diff --git a/tests/float.rs b/tests/float.rs
index 94ec7a03..8d70c7b3 100644
--- a/tests/float.rs
+++ b/tests/float.rs
@@ -4,7 +4,7 @@ use rhai::{Engine, EvalAltResult, RegisterFn, FLOAT};
 const EPSILON: FLOAT = 0.000_000_000_1;
 
 #[test]
-fn test_float() -> Result<(), EvalAltResult> {
+fn test_float() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -22,7 +22,7 @@ fn test_float() -> Result<(), EvalAltResult> {
 
 #[test]
 #[cfg(not(feature = "no_object"))]
-fn struct_with_float() -> Result<(), EvalAltResult> {
+fn struct_with_float() -> Result<(), Box<EvalAltResult>> {
     #[derive(Clone)]
     struct TestStruct {
         x: f64,
diff --git a/tests/for.rs b/tests/for.rs
index f36f3ae3..081fddb9 100644
--- a/tests/for.rs
+++ b/tests/for.rs
@@ -2,7 +2,7 @@ use rhai::{Engine, EvalAltResult, INT};
 
 #[cfg(not(feature = "no_index"))]
 #[test]
-fn test_for_array() -> Result<(), EvalAltResult> {
+fn test_for_array() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let script = r"
@@ -32,7 +32,7 @@ fn test_for_array() -> Result<(), EvalAltResult> {
 
 #[cfg(not(feature = "no_object"))]
 #[test]
-fn test_for_object() -> Result<(), EvalAltResult> {
+fn test_for_object() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let script = r#"
diff --git a/tests/get_set.rs b/tests/get_set.rs
index 9f63a365..5859ea2e 100644
--- a/tests/get_set.rs
+++ b/tests/get_set.rs
@@ -3,7 +3,7 @@
 use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
 #[test]
-fn test_get_set() -> Result<(), EvalAltResult> {
+fn test_get_set() -> Result<(), Box<EvalAltResult>> {
     #[derive(Clone)]
     struct TestStruct {
         x: INT,
@@ -36,7 +36,7 @@ fn test_get_set() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_big_get_set() -> Result<(), EvalAltResult> {
+fn test_big_get_set() -> Result<(), Box<EvalAltResult>> {
     #[derive(Clone)]
     struct TestChild {
         x: INT,
diff --git a/tests/if_block.rs b/tests/if_block.rs
index dcde8143..a5d5125a 100644
--- a/tests/if_block.rs
+++ b/tests/if_block.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_if() -> Result<(), EvalAltResult> {
+fn test_if() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("if true { 55 }")?, 55);
@@ -29,7 +29,7 @@ fn test_if() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_if_expr() -> Result<(), EvalAltResult> {
+fn test_if_expr() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/increment.rs b/tests/increment.rs
index 9642af0a..f622ab21 100644
--- a/tests/increment.rs
+++ b/tests/increment.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_increment() -> Result<(), EvalAltResult> {
+fn test_increment() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 1; x += 2; x")?, 3);
diff --git a/tests/internal_fn.rs b/tests/internal_fn.rs
index cc99187a..764cf601 100644
--- a/tests/internal_fn.rs
+++ b/tests/internal_fn.rs
@@ -3,7 +3,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_internal_fn() -> Result<(), EvalAltResult> {
+fn test_internal_fn() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -16,7 +16,7 @@ fn test_internal_fn() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_big_internal_fn() -> Result<(), EvalAltResult> {
+fn test_big_internal_fn() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -35,7 +35,7 @@ fn test_big_internal_fn() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_internal_fn_overloading() -> Result<(), EvalAltResult> {
+fn test_internal_fn_overloading() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/looping.rs b/tests/looping.rs
index c7aace27..a973c98f 100644
--- a/tests/looping.rs
+++ b/tests/looping.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_loop() -> Result<(), EvalAltResult> {
+fn test_loop() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/maps.rs b/tests/maps.rs
index c1b91187..897f8430 100644
--- a/tests/maps.rs
+++ b/tests/maps.rs
@@ -3,7 +3,7 @@
 use rhai::{Engine, EvalAltResult, Map, Scope, INT};
 
 #[test]
-fn test_map_indexing() -> Result<(), EvalAltResult> {
+fn test_map_indexing() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     #[cfg(not(feature = "no_index"))]
@@ -81,7 +81,7 @@ fn test_map_indexing() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_map_assign() -> Result<(), EvalAltResult> {
+fn test_map_assign() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let x = engine.eval::<Map>(r#"let x = #{a: 1, b: true, "c$": "hello"}; x"#)?;
@@ -112,7 +112,7 @@ fn test_map_assign() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_map_return() -> Result<(), EvalAltResult> {
+fn test_map_return() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let x = engine.eval::<Map>(r#"#{a: 1, b: true, "c$": "hello"}"#)?;
@@ -143,7 +143,7 @@ fn test_map_return() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_map_for() -> Result<(), EvalAltResult> {
+fn test_map_for() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -170,7 +170,7 @@ fn test_map_for() -> Result<(), EvalAltResult> {
 #[test]
 /// Because a Rhai object map literal is almost the same as JSON,
 /// it is possible to convert from JSON into a Rhai object map.
-fn test_map_json() -> Result<(), EvalAltResult> {
+fn test_map_json() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     let json = r#"{"a":1, "b":true, "c":42, "$d e f!":"hello", "z":null}"#;
diff --git a/tests/math.rs b/tests/math.rs
index 500b35b8..4e4a5d4b 100644
--- a/tests/math.rs
+++ b/tests/math.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_math() -> Result<(), EvalAltResult> {
+fn test_math() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("1 + 2")?, 3);
@@ -25,37 +25,37 @@ fn test_math() -> Result<(), EvalAltResult> {
         #[cfg(not(feature = "only_i32"))]
         {
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("abs(-9223372036854775808)")
                     .expect_err("expects negation overflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("9223372036854775807 + 1")
                     .expect_err("expects overflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("-9223372036854775808 - 1")
                     .expect_err("expects underflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("9223372036854775807 * 9223372036854775807")
                     .expect_err("expects overflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("9223372036854775807 / 0")
                     .expect_err("expects division by zero"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("9223372036854775807 % 0")
                     .expect_err("expects division by zero"),
                 EvalAltResult::ErrorArithmetic(_, _)
@@ -65,31 +65,31 @@ fn test_math() -> Result<(), EvalAltResult> {
         #[cfg(feature = "only_i32")]
         {
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("2147483647 + 1")
                     .expect_err("expects overflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("-2147483648 - 1")
                     .expect_err("expects underflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("2147483647 * 2147483647")
                     .expect_err("expects overflow"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("2147483647 / 0")
                     .expect_err("expects division by zero"),
                 EvalAltResult::ErrorArithmetic(_, _)
             ));
             assert!(matches!(
-                engine
+                *engine
                     .eval::<INT>("2147483647 % 0")
                     .expect_err("expects division by zero"),
                 EvalAltResult::ErrorArithmetic(_, _)
diff --git a/tests/method_call.rs b/tests/method_call.rs
index a4e19251..99d1d0bd 100644
--- a/tests/method_call.rs
+++ b/tests/method_call.rs
@@ -3,7 +3,7 @@
 use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
 #[test]
-fn test_method_call() -> Result<(), EvalAltResult> {
+fn test_method_call() -> Result<(), Box<EvalAltResult>> {
     #[derive(Debug, Clone, Eq, PartialEq)]
     struct TestStruct {
         x: INT,
diff --git a/tests/mismatched_op.rs b/tests/mismatched_op.rs
index e6e6e15d..b129f29b 100644
--- a/tests/mismatched_op.rs
+++ b/tests/mismatched_op.rs
@@ -4,10 +4,10 @@ use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 fn test_mismatched_op() {
     let engine = Engine::new();
 
-    assert!(
-        matches!(engine.eval::<INT>(r#""hello, " + "world!""#).expect_err("expects error"),
-        EvalAltResult::ErrorMismatchOutputType(err, _) if err == "string")
-    );
+    assert!(matches!(
+        *engine.eval::<INT>(r#""hello, " + "world!""#).expect_err("expects error"),
+        EvalAltResult::ErrorMismatchOutputType(err, _) if err == "string"
+    ));
 }
 
 #[test]
@@ -33,12 +33,14 @@ fn test_mismatched_op_custom_type() {
         .expect_err("expects error");
 
     #[cfg(feature = "only_i32")]
-    assert!(
-        matches!(r, EvalAltResult::ErrorFunctionNotFound(err, _) if err == "+ (i32, TestStruct)")
-    );
+    assert!(matches!(
+        *r,
+        EvalAltResult::ErrorFunctionNotFound(err, _) if err == "+ (i32, TestStruct)"
+    ));
 
     #[cfg(not(feature = "only_i32"))]
-    assert!(
-        matches!(r, EvalAltResult::ErrorFunctionNotFound(err, _) if err == "+ (i64, TestStruct)")
-    );
+    assert!(matches!(
+        *r,
+        EvalAltResult::ErrorFunctionNotFound(err, _) if err == "+ (i64, TestStruct)"
+    ));
 }
diff --git a/tests/not.rs b/tests/not.rs
index 4ce9cd3e..ffc1d21d 100644
--- a/tests/not.rs
+++ b/tests/not.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult};
 
 #[test]
-fn test_not() -> Result<(), EvalAltResult> {
+fn test_not() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/number_literals.rs b/tests/number_literals.rs
index 3fe8c78f..699de19a 100644
--- a/tests/number_literals.rs
+++ b/tests/number_literals.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_number_literal() -> Result<(), EvalAltResult> {
+fn test_number_literal() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("65")?, 65);
@@ -10,7 +10,7 @@ fn test_number_literal() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_hex_literal() -> Result<(), EvalAltResult> {
+fn test_hex_literal() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 0xf; x")?, 15);
@@ -20,7 +20,7 @@ fn test_hex_literal() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_octal_literal() -> Result<(), EvalAltResult> {
+fn test_octal_literal() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 0o77; x")?, 63);
@@ -30,7 +30,7 @@ fn test_octal_literal() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_binary_literal() -> Result<(), EvalAltResult> {
+fn test_binary_literal() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 0b1111; x")?, 15);
diff --git a/tests/ops.rs b/tests/ops.rs
index c817d65d..e087a8d0 100644
--- a/tests/ops.rs
+++ b/tests/ops.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_ops() -> Result<(), EvalAltResult> {
+fn test_ops() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("60 + 5")?, 65);
@@ -11,7 +11,7 @@ fn test_ops() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_op_precedence() -> Result<(), EvalAltResult> {
+fn test_op_precedence() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/optimizer.rs b/tests/optimizer.rs
index eb9f1d5c..49b15c25 100644
--- a/tests/optimizer.rs
+++ b/tests/optimizer.rs
@@ -3,8 +3,8 @@
 use rhai::{Engine, EvalAltResult, OptimizationLevel, INT};
 
 #[test]
-fn test_optimizer() -> Result<(), EvalAltResult> {
-    fn run_test(engine: &mut Engine) -> Result<(), EvalAltResult> {
+fn test_optimizer() -> Result<(), Box<EvalAltResult>> {
+    fn run_test(engine: &mut Engine) -> Result<(), Box<EvalAltResult>> {
         assert_eq!(engine.eval::<INT>(r"if true { 42 } else { 123 }")?, 42);
         assert_eq!(
             engine.eval::<INT>(r"if 1 == 1 || 2 > 3 { 42 } else { 123 }")?,
diff --git a/tests/power_of.rs b/tests/power_of.rs
index 3762ff0f..a3b6fd43 100644
--- a/tests/power_of.rs
+++ b/tests/power_of.rs
@@ -7,7 +7,7 @@ use rhai::FLOAT;
 const EPSILON: FLOAT = 0.000_000_000_1;
 
 #[test]
-fn test_power_of() -> Result<(), EvalAltResult> {
+fn test_power_of() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("2 ~ 3")?, 8);
@@ -28,7 +28,7 @@ fn test_power_of() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_power_of_equals() -> Result<(), EvalAltResult> {
+fn test_power_of_equals() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = 2; x ~= 3; x")?, 8);
diff --git a/tests/side_effects.rs b/tests/side_effects.rs
index 259d1f63..fb364747 100644
--- a/tests/side_effects.rs
+++ b/tests/side_effects.rs
@@ -40,7 +40,7 @@ impl CommandWrapper {
 
 #[cfg(not(feature = "no_object"))]
 #[test]
-fn test_side_effects_command() -> Result<(), EvalAltResult> {
+fn test_side_effects_command() -> Result<(), Box<EvalAltResult>> {
     let mut engine = Engine::new();
     let mut scope = Scope::new();
 
@@ -80,7 +80,7 @@ fn test_side_effects_command() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_side_effects_print() -> Result<(), EvalAltResult> {
+fn test_side_effects_print() -> Result<(), Box<EvalAltResult>> {
     use std::sync::Arc;
     use std::sync::RwLock;
 
diff --git a/tests/stack.rs b/tests/stack.rs
index 8efc759e..503bcbde 100644
--- a/tests/stack.rs
+++ b/tests/stack.rs
@@ -2,7 +2,7 @@
 use rhai::{Engine, EvalAltResult};
 
 #[test]
-fn test_stack_overflow() -> Result<(), EvalAltResult> {
+fn test_stack_overflow() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -22,8 +22,10 @@ fn test_stack_overflow() -> Result<(), EvalAltResult> {
     ",
     ) {
         Ok(_) => panic!("should be stack overflow"),
-        Err(EvalAltResult::ErrorStackOverflow(_)) => (),
-        Err(_) => panic!("should be stack overflow"),
+        Err(err) => match *err {
+            EvalAltResult::ErrorStackOverflow(_) => (),
+            _ => panic!("should be stack overflow"),
+        },
     }
 
     Ok(())
diff --git a/tests/string.rs b/tests/string.rs
index 1ec77e2e..981d19eb 100644
--- a/tests/string.rs
+++ b/tests/string.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_string() -> Result<(), EvalAltResult> {
+fn test_string() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
@@ -37,7 +37,7 @@ fn test_string() -> Result<(), EvalAltResult> {
 #[cfg(not(feature = "no_stdlib"))]
 #[cfg(not(feature = "no_object"))]
 #[test]
-fn test_string_substring() -> Result<(), EvalAltResult> {
+fn test_string_substring() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(
diff --git a/tests/throw.rs b/tests/throw.rs
index 6e55303c..5f5c58a0 100644
--- a/tests/throw.rs
+++ b/tests/throw.rs
@@ -5,10 +5,12 @@ fn test_throw() {
     let engine = Engine::new();
 
     assert!(matches!(
-        engine.eval::<()>(r#"if true { throw "hello" }"#).expect_err("expects error"),
-        EvalAltResult::ErrorRuntime(s, _) if s == "hello"));
+        *engine.eval::<()>(r#"if true { throw "hello" }"#).expect_err("expects error"),
+        EvalAltResult::ErrorRuntime(s, _) if s == "hello"
+    ));
 
     assert!(matches!(
-        engine.eval::<()>(r#"throw"#).expect_err("expects error"),
-        EvalAltResult::ErrorRuntime(s, _) if s == ""));
+        *engine.eval::<()>(r#"throw"#).expect_err("expects error"),
+        EvalAltResult::ErrorRuntime(s, _) if s == ""
+    ));
 }
diff --git a/tests/time.rs b/tests/time.rs
index eddb652d..aa5239b1 100644
--- a/tests/time.rs
+++ b/tests/time.rs
@@ -7,7 +7,7 @@ use rhai::{Engine, EvalAltResult, INT};
 use rhai::FLOAT;
 
 #[test]
-fn test_timestamp() -> Result<(), EvalAltResult> {
+fn test_timestamp() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<String>("type_of(timestamp())")?, "timestamp");
diff --git a/tests/types.rs b/tests/types.rs
index 658d8b3f..d5a5928e 100644
--- a/tests/types.rs
+++ b/tests/types.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, RegisterFn, INT};
 
 #[test]
-fn test_type_of() -> Result<(), EvalAltResult> {
+fn test_type_of() -> Result<(), Box<EvalAltResult>> {
     #[derive(Clone)]
     struct TestStruct {
         x: INT,
diff --git a/tests/unary_after_binary.rs b/tests/unary_after_binary.rs
index ba74c9f9..d2366be7 100644
--- a/tests/unary_after_binary.rs
+++ b/tests/unary_after_binary.rs
@@ -3,7 +3,7 @@ use rhai::{Engine, EvalAltResult, INT};
 #[test]
 // TODO also add test case for unary after compound
 // Hah, turns out unary + has a good use after all!
-fn test_unary_after_binary() -> Result<(), EvalAltResult> {
+fn test_unary_after_binary() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("10 % +4")?, 2);
diff --git a/tests/unary_minus.rs b/tests/unary_minus.rs
index e1a359d7..87e2aa2b 100644
--- a/tests/unary_minus.rs
+++ b/tests/unary_minus.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_unary_minus() -> Result<(), EvalAltResult> {
+fn test_unary_minus() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(engine.eval::<INT>("let x = -5; x")?, -5);
diff --git a/tests/unit.rs b/tests/unit.rs
index 465c7b48..2777ae54 100644
--- a/tests/unit.rs
+++ b/tests/unit.rs
@@ -1,21 +1,21 @@
 use rhai::{Engine, EvalAltResult};
 
 #[test]
-fn test_unit() -> Result<(), EvalAltResult> {
+fn test_unit() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     engine.eval::<()>("let x = (); x")?;
     Ok(())
 }
 
 #[test]
-fn test_unit_eq() -> Result<(), EvalAltResult> {
+fn test_unit_eq() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     assert_eq!(engine.eval::<bool>("let x = (); let y = (); x == y")?, true);
     Ok(())
 }
 
 #[test]
-fn test_unit_with_spaces() -> Result<(), EvalAltResult> {
+fn test_unit_with_spaces() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     engine.eval::<()>("let x = ( ); x")?;
     Ok(())
diff --git a/tests/var_scope.rs b/tests/var_scope.rs
index 8d5244c8..fde83a05 100644
--- a/tests/var_scope.rs
+++ b/tests/var_scope.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, Scope, INT};
 
 #[test]
-fn test_var_scope() -> Result<(), EvalAltResult> {
+fn test_var_scope() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
     let mut scope = Scope::new();
 
@@ -20,7 +20,7 @@ fn test_var_scope() -> Result<(), EvalAltResult> {
 }
 
 #[test]
-fn test_scope_eval() -> Result<(), EvalAltResult> {
+fn test_scope_eval() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     // First create the state
diff --git a/tests/while_loop.rs b/tests/while_loop.rs
index 3a035039..8916cd7c 100644
--- a/tests/while_loop.rs
+++ b/tests/while_loop.rs
@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, INT};
 
 #[test]
-fn test_while() -> Result<(), EvalAltResult> {
+fn test_while() -> Result<(), Box<EvalAltResult>> {
     let engine = Engine::new();
 
     assert_eq!(