diff --git a/CHANGELOG.md b/CHANGELOG.md
index b6f6d5c7..f73ee408 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,11 +26,11 @@ New features
 * Normal loops return `()` as the value.
 * Loop expressions can be enabled/disabled via `Engine::set_allow_loop_expressions`
 
-### Stable hashing
+### Static hashing
 
-* It is now possible to specify a fixed _seed_ for use with the `ahash` hasher, via an environment variable, in order to force stable (i.e. deterministic) hashes for function signatures.
+* It is now possible to specify a fixed _seed_ for use with the `ahash` hasher, via a static function `rhai::config::hashing::set_ahash_seed` or an environment variable, in order to force static (i.e. deterministic) hashes for function signatures.
 * This is necessary when using Rhai across shared-library boundaries.
-* A build script is used to extract the environment variable (`RHAI_AHASH_SEED`) and splice it into the source code before compilation.
+* A build script is used to extract the environment variable (`RHAI_AHASH_SEED`, if any) and splice it into the source code before compilation.
 
 ### No Timestamps
 
diff --git a/build.template b/build.template
index a165e5ed..bce322e8 100644
--- a/build.template
+++ b/build.template
@@ -1,2 +1,3 @@
-// This file is automatically set during build time by build.rs and build.template.
+//! This file is automatically recreated during build time by `build.rs` from `build.template`.
+
 pub(crate) const AHASH_SEED: Option<[u64; 4]> = {{AHASH_SEED}};
diff --git a/src/api/call_fn.rs b/src/api/call_fn.rs
index 3b0a7615..1a9e2347 100644
--- a/src/api/call_fn.rs
+++ b/src/api/call_fn.rs
@@ -259,35 +259,36 @@ impl Engine {
             ast.resolver().cloned(),
         );
 
-        let mut result = Ok(Dynamic::UNIT);
-
-        if eval_ast && !statements.is_empty() {
-            result = self.eval_global_statements(scope, global, caches, statements, lib, 0);
+        let result = if eval_ast && !statements.is_empty() {
+            let r = self.eval_global_statements(global, caches, lib, 0, scope, statements);
 
             if rewind_scope {
                 scope.rewind(orig_scope_len);
             }
-        }
 
-        result = result.and_then(|_| {
+            r
+        } else {
+            Ok(Dynamic::UNIT)
+        }
+        .and_then(|_| {
             let mut args: StaticVec<_> = arg_values.iter_mut().collect();
 
             // Check for data race.
             #[cfg(not(feature = "no_closure"))]
-            crate::func::call::ensure_no_data_race(name, &args, false).map(|_| Dynamic::UNIT)?;
+            crate::func::ensure_no_data_race(name, &args, false).map(|_| Dynamic::UNIT)?;
 
             if let Some(fn_def) = ast.shared_lib().get_script_fn(name, args.len()) {
                 self.call_script_fn(
-                    scope,
                     global,
                     caches,
                     lib,
+                    0,
+                    scope,
                     &mut this_ptr,
                     fn_def,
                     &mut args,
                     rewind_scope,
                     Position::NONE,
-                    0,
                 )
             } else {
                 Err(ERR::ErrorFunctionNotFound(name.into(), Position::NONE).into())
@@ -305,7 +306,7 @@ impl Engine {
         if self.debugger.is_some() {
             global.debugger.status = crate::eval::DebuggerStatus::Terminate;
             let node = &crate::ast::Stmt::Noop(Position::NONE);
-            self.run_debugger(scope, global, lib, &mut this_ptr, node, 0)?;
+            self.run_debugger(global, caches, lib, 0, scope, &mut this_ptr, node)?;
         }
 
         Ok(result)
diff --git a/src/api/custom_syntax.rs b/src/api/custom_syntax.rs
index 868b9931..a12ea593 100644
--- a/src/api/custom_syntax.rs
+++ b/src/api/custom_syntax.rs
@@ -228,7 +228,13 @@ impl Engine {
                 continue;
             }
 
-            let token = Token::lookup_from_syntax(s);
+            let token = Token::lookup_symbol_from_syntax(s).or_else(|| {
+                if Token::is_reserved_keyword(s) {
+                    Some(Token::Reserved(Box::new(s.into())))
+                } else {
+                    None
+                }
+            });
 
             let seg = match s {
                 // Markers not in first position
@@ -273,7 +279,7 @@ impl Engine {
                     .into_err(Position::NONE));
                 }
                 // Identifier in first position
-                _ if segments.is_empty() && is_valid_identifier(s.chars()) => {
+                _ if segments.is_empty() && is_valid_identifier(s) => {
                     // Make it a custom keyword/symbol if it is disabled or reserved
                     if (!self.disabled_symbols.is_empty() && self.disabled_symbols.contains(s))
                         || token.map_or(false, |v| v.is_reserved())
diff --git a/src/api/eval.rs b/src/api/eval.rs
index 3f37264d..ffef8623 100644
--- a/src/api/eval.rs
+++ b/src/api/eval.rs
@@ -186,8 +186,9 @@ impl Engine {
         ast: &AST,
     ) -> RhaiResultOf<T> {
         let global = &mut GlobalRuntimeState::new(self);
+        let caches = &mut Caches::new();
 
-        let result = self.eval_ast_with_scope_raw(scope, global, ast, 0)?;
+        let result = self.eval_ast_with_scope_raw(global, caches, 0, scope, ast)?;
 
         #[cfg(feature = "debugging")]
         if self.debugger.is_some() {
@@ -197,7 +198,7 @@ impl Engine {
                 ast.as_ref(),
             ];
             let node = &crate::ast::Stmt::Noop(Position::NONE);
-            self.run_debugger(scope, global, lib, &mut None, node, 0)?;
+            self.run_debugger(global, caches, lib, 0, scope, &mut None, node)?;
         }
 
         let typ = self.map_type_name(result.type_name());
@@ -211,12 +212,12 @@ impl Engine {
     #[inline]
     pub(crate) fn eval_ast_with_scope_raw<'a>(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
-        ast: &'a AST,
+        caches: &mut Caches,
         level: usize,
+        scope: &mut Scope,
+        ast: &'a AST,
     ) -> RhaiResult {
-        let mut caches = Caches::new();
         global.source = ast.source_raw().cloned();
 
         #[cfg(not(feature = "no_module"))]
@@ -240,8 +241,7 @@ impl Engine {
             _lib = &[];
         }
 
-        let result =
-            self.eval_global_statements(scope, global, &mut caches, statements, _lib, level);
+        let result = self.eval_global_statements(global, caches, _lib, level, scope, statements);
 
         #[cfg(not(feature = "no_module"))]
         {
@@ -262,14 +262,14 @@ impl Engine {
     #[inline(always)]
     pub fn eval_statements_raw(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
-        statements: &[crate::ast::Stmt],
         lib: &[&crate::Module],
         level: usize,
+        scope: &mut Scope,
+        statements: &[crate::ast::Stmt],
     ) -> RhaiResult {
-        self.eval_global_statements(scope, global, caches, statements, lib, level)
+        self.eval_global_statements(global, caches, lib, level, scope, statements)
     }
 }
 
diff --git a/src/api/mod.rs b/src/api/mod.rs
index 5f85f140..71973732 100644
--- a/src/api/mod.rs
+++ b/src/api/mod.rs
@@ -154,7 +154,7 @@ impl Engine {
 
         let keyword = keyword.as_ref();
 
-        match Token::lookup_from_syntax(keyword) {
+        match Token::lookup_symbol_from_syntax(keyword) {
             // Standard identifiers and reserved keywords are OK
             None | Some(Token::Reserved(..)) => (),
             // custom keywords are OK
diff --git a/src/api/run.rs b/src/api/run.rs
index e32136e6..effdd4b6 100644
--- a/src/api/run.rs
+++ b/src/api/run.rs
@@ -131,7 +131,7 @@ impl Engine {
             } else {
                 &lib
             };
-            self.eval_global_statements(scope, global, caches, statements, lib, 0)?;
+            self.eval_global_statements(global, caches, lib, 0, scope, statements)?;
         }
 
         #[cfg(feature = "debugging")]
@@ -142,7 +142,7 @@ impl Engine {
                 ast.as_ref(),
             ];
             let node = &crate::ast::Stmt::Noop(crate::Position::NONE);
-            self.run_debugger(scope, global, lib, &mut None, node, 0)?;
+            self.run_debugger(global, caches, lib, 0, scope, &mut None, node)?;
         }
 
         Ok(())
diff --git a/src/api/type_names.rs b/src/api/type_names.rs
index f7897bf0..dda879fc 100644
--- a/src/api/type_names.rs
+++ b/src/api/type_names.rs
@@ -108,11 +108,15 @@ fn map_std_type_name(name: &str, shorthands: bool) -> &str {
 
 /// Format a Rust type to be display-friendly.
 ///
+/// * `rhai::` prefix is cleared.
 /// * `()` is cleared.
+/// * `&mut` is cleared.
 /// * `INT` and `FLOAT` are expanded.
 /// * [`RhaiResult`][crate::RhaiResult] and [`RhaiResultOf<T>`][crate::RhaiResultOf] are expanded.
 #[cfg(feature = "metadata")]
 pub fn format_type(typ: &str, is_return_type: bool) -> std::borrow::Cow<str> {
+    const RESULT_TYPE: &str = "Result<";
+    const ERROR_TYPE: &str = ",Box<EvalAltResult>>";
     const RHAI_RESULT_TYPE: &str = "RhaiResult";
     const RHAI_RESULT_TYPE_EXPAND: &str = "Result<Dynamic, Box<EvalAltResult>>";
     const RHAI_RESULT_OF_TYPE: &str = "RhaiResultOf<";
@@ -135,6 +139,10 @@ pub fn format_type(typ: &str, is_return_type: bool) -> std::borrow::Cow<str> {
         } else {
             format!("&mut {r}").into()
         };
+    } else if typ.contains(" ") {
+        let typ = typ.replace(" ", "");
+        let r = format_type(&typ, is_return_type);
+        return r.into_owned().into();
     }
 
     match typ {
@@ -167,6 +175,12 @@ pub fn format_type(typ: &str, is_return_type: bool) -> std::borrow::Cow<str> {
                 .replace("{}", format_type(inner, false).trim())
                 .into()
         }
+        ty if ty.starts_with(RESULT_TYPE) && ty.ends_with(ERROR_TYPE) => {
+            let inner = &ty[RESULT_TYPE.len()..ty.len() - ERROR_TYPE.len()];
+            RHAI_RESULT_OF_TYPE_EXPAND
+                .replace("{}", format_type(inner, false).trim())
+                .into()
+        }
         ty => ty.into(),
     }
 }
diff --git a/src/ast/expr.rs b/src/ast/expr.rs
index 863299c8..163fdbc9 100644
--- a/src/ast/expr.rs
+++ b/src/ast/expr.rs
@@ -17,7 +17,7 @@ use std::{
     fmt::Write,
     hash::Hash,
     iter::once,
-    num::{NonZeroU8, NonZeroUsize},
+    num::{NonZeroU64, NonZeroU8, NonZeroUsize},
 };
 
 #[cfg(not(feature = "no_float"))]
@@ -86,7 +86,7 @@ impl CustomExpr {
 ///
 /// Two separate hashes are pre-calculated because of the following patterns:
 ///
-/// ```js
+/// ```rhai
 /// func(a, b, c);      // Native: func(a, b, c)        - 3 parameters
 ///                     // Script: func(a, b, c)        - 3 parameters
 ///
@@ -100,20 +100,22 @@ impl CustomExpr {
 ///
 /// Function call hashes are used in the following manner:
 ///
-/// * First, the script hash is tried, which contains only the called function's name plus the
-///   number of parameters.
+/// * First, the script hash (if any) is tried, which contains only the called function's name plus
+///   the number of parameters.
 ///
 /// * Next, the actual types of arguments are hashed and _combined_ with the native hash, which is
-///   then used to search for a native function. In other words, a complete native function call
-///   hash always contains the called function's name plus the types of the arguments.  This is due
-///   to possible function overloading for different parameter types.
-#[derive(Clone, Copy, Eq, PartialEq, Hash, Default)]
+///   then used to search for a native function.
+///
+///   In other words, a complete native function call hash always contains the called function's
+///   name plus the types of the arguments.  This is due to possible function overloading for
+///   different parameter types.
+#[derive(Clone, Copy, Eq, PartialEq, Hash)]
 pub struct FnCallHashes {
-    /// Pre-calculated hash for a script-defined function (zero if native functions only).
+    /// Pre-calculated hash for a script-defined function ([`None`] if native functions only).
     #[cfg(not(feature = "no_function"))]
-    pub script: u64,
+    script: Option<NonZeroU64>,
     /// Pre-calculated hash for a native Rust function with no parameter types.
-    pub native: u64,
+    native: NonZeroU64,
 }
 
 impl fmt::Debug for FnCallHashes {
@@ -121,11 +123,11 @@ impl fmt::Debug for FnCallHashes {
     #[inline(never)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         #[cfg(not(feature = "no_function"))]
-        if self.script != 0 {
-            return if self.script == self.native {
+        if let Some(script) = self.script {
+            return if script == self.native {
                 fmt::Debug::fmt(&self.native, f)
             } else {
-                write!(f, "({}, {})", self.script, self.native)
+                write!(f, "({}, {})", script, self.native)
             };
         }
 
@@ -136,11 +138,11 @@ impl fmt::Debug for FnCallHashes {
 impl From<u64> for FnCallHashes {
     #[inline]
     fn from(hash: u64) -> Self {
-        let hash = if hash == 0 { ALT_ZERO_HASH } else { hash };
+        let hash = NonZeroU64::new(if hash == 0 { ALT_ZERO_HASH } else { hash }).unwrap();
 
         Self {
             #[cfg(not(feature = "no_function"))]
-            script: hash,
+            script: Some(hash),
             native: hash,
         }
     }
@@ -150,33 +152,54 @@ impl FnCallHashes {
     /// Create a [`FnCallHashes`] with only the native Rust hash.
     #[inline]
     #[must_use]
-    pub const fn from_native(hash: u64) -> Self {
+    pub fn from_native(hash: u64) -> Self {
         Self {
             #[cfg(not(feature = "no_function"))]
-            script: 0,
-            native: if hash == 0 { ALT_ZERO_HASH } else { hash },
+            script: None,
+            native: NonZeroU64::new(if hash == 0 { ALT_ZERO_HASH } else { hash }).unwrap(),
         }
     }
     /// Create a [`FnCallHashes`] with both native Rust and script function hashes.
     #[inline]
     #[must_use]
-    pub const fn from_all(#[cfg(not(feature = "no_function"))] script: u64, native: u64) -> Self {
+    pub fn from_all(#[cfg(not(feature = "no_function"))] script: u64, native: u64) -> Self {
         Self {
             #[cfg(not(feature = "no_function"))]
-            script: if script == 0 { ALT_ZERO_HASH } else { script },
-            native: if native == 0 { ALT_ZERO_HASH } else { native },
+            script: NonZeroU64::new(if script == 0 { ALT_ZERO_HASH } else { script }),
+            native: NonZeroU64::new(if native == 0 { ALT_ZERO_HASH } else { native }).unwrap(),
         }
     }
-    /// Is this [`FnCallHashes`] native Rust only?
+    /// Is this [`FnCallHashes`] native-only?
     #[inline(always)]
     #[must_use]
     pub const fn is_native_only(&self) -> bool {
         #[cfg(not(feature = "no_function"))]
-        return self.script == 0;
-
+        return self.script.is_none();
         #[cfg(feature = "no_function")]
         return true;
     }
+    /// Get the native hash.
+    ///
+    /// The hash returned is never zero.
+    #[inline(always)]
+    #[must_use]
+    pub fn native(&self) -> u64 {
+        self.native.get()
+    }
+    /// Get the script hash.
+    ///
+    /// The hash returned is never zero.
+    ///
+    /// # Panics
+    ///
+    /// Panics if this [`FnCallHashes`] is native-only.
+    #[cfg(not(feature = "no_function"))]
+    #[inline(always)]
+    #[must_use]
+    pub fn script(&self) -> u64 {
+        assert!(self.script.is_some());
+        self.script.as_ref().unwrap().get()
+    }
 }
 
 /// _(internals)_ A function call.
@@ -195,12 +218,7 @@ pub struct FnCallExpr {
     /// Does this function call capture the parent scope?
     pub capture_parent_scope: bool,
     /// Is this function call a native operator?
-    pub operator_token: Option<Token>,
-    /// Can this function call be a scripted function?
-    #[cfg(not(feature = "no_function"))]
-    pub can_be_script: bool,
-    /// [Position] of the function name.
-    pub pos: Position,
+    pub op_token: Option<Token>,
 }
 
 impl fmt::Debug for FnCallExpr {
@@ -215,17 +233,12 @@ impl fmt::Debug for FnCallExpr {
         ff.field("hash", &self.hashes)
             .field("name", &self.name)
             .field("args", &self.args);
-        if let Some(ref token) = self.operator_token {
-            ff.field("operator_token", token);
+        if let Some(ref token) = self.op_token {
+            ff.field("op_token", token);
         }
         if self.capture_parent_scope {
             ff.field("capture_parent_scope", &self.capture_parent_scope);
         }
-        #[cfg(not(feature = "no_function"))]
-        if self.can_be_script {
-            ff.field("can_be_script", &self.can_be_script);
-        }
-        ff.field("pos", &self.pos);
         ff.finish()
     }
 }
@@ -248,6 +261,16 @@ impl FnCallExpr {
     pub fn into_fn_call_expr(self, pos: Position) -> Expr {
         Expr::FnCall(self.into(), pos)
     }
+    /// Are all arguments constant?
+    #[inline]
+    #[must_use]
+    pub fn constant_args(&self) -> bool {
+        if self.args.is_empty() {
+            true
+        } else {
+            self.args.iter().all(Expr::is_constant)
+        }
+    }
 }
 
 /// A type that wraps a floating-point number and implements [`Hash`].
@@ -690,10 +713,7 @@ impl Expr {
                     hashes: calc_fn_hash(None, f.fn_name(), 1).into(),
                     args: once(Self::StringConstant(f.fn_name().into(), pos)).collect(),
                     capture_parent_scope: false,
-                    operator_token: None,
-                    #[cfg(not(feature = "no_function"))]
-                    can_be_script: true,
-                    pos,
+                    op_token: None,
                 }
                 .into(),
                 pos,
@@ -748,6 +768,8 @@ impl Expr {
             | Self::And(.., pos)
             | Self::Or(.., pos)
             | Self::Coalesce(.., pos)
+            | Self::FnCall(.., pos)
+            | Self::MethodCall(.., pos)
             | Self::Index(.., pos)
             | Self::Dot(.., pos)
             | Self::InterpolatedString(.., pos)
@@ -756,8 +778,6 @@ impl Expr {
             #[cfg(not(feature = "no_custom_syntax"))]
             Self::Custom(.., pos) => *pos,
 
-            Self::FnCall(x, ..) | Self::MethodCall(x, ..) => x.pos,
-
             Self::Stmt(x) => x.position(),
         }
     }
diff --git a/src/ast/flags.rs b/src/ast/flags.rs
index e26fb55c..452a57e6 100644
--- a/src/ast/flags.rs
+++ b/src/ast/flags.rs
@@ -18,7 +18,7 @@ pub enum FnAccess {
 
 impl FnAccess {
     /// Is this function private?
-    #[inline]
+    #[inline(always)]
     #[must_use]
     pub const fn is_private(self) -> bool {
         match self {
@@ -27,7 +27,7 @@ impl FnAccess {
         }
     }
     /// Is this function public?
-    #[inline]
+    #[inline(always)]
     #[must_use]
     pub const fn is_public(self) -> bool {
         match self {
diff --git a/src/ast/stmt.rs b/src/ast/stmt.rs
index e272e1e9..541332c3 100644
--- a/src/ast/stmt.rs
+++ b/src/ast/stmt.rs
@@ -61,7 +61,10 @@ impl OpAssignment {
     #[must_use]
     #[inline(always)]
     pub fn new_op_assignment(name: &str, pos: Position) -> Self {
-        Self::new_op_assignment_from_token(&Token::lookup_from_syntax(name).expect("operator"), pos)
+        Self::new_op_assignment_from_token(
+            &Token::lookup_symbol_from_syntax(name).expect("operator"),
+            pos,
+        )
     }
     /// Create a new [`OpAssignment`] from a [`Token`].
     ///
@@ -90,7 +93,7 @@ impl OpAssignment {
     #[inline(always)]
     pub fn new_op_assignment_from_base(name: &str, pos: Position) -> Self {
         Self::new_op_assignment_from_base_token(
-            &Token::lookup_from_syntax(name).expect("operator"),
+            &Token::lookup_symbol_from_syntax(name).expect("operator"),
             pos,
         )
     }
diff --git a/src/config/hashing.rs b/src/config/hashing.rs
index 2355a405..58374d21 100644
--- a/src/config/hashing.rs
+++ b/src/config/hashing.rs
@@ -2,18 +2,30 @@
 //!
 //! Set to [`None`] to disable stable hashing.
 //!
-//! See [`set_rhai_ahash_seed`] for more.
+//! See [`set_rhai_ahash_seed`].
 //!
-//! Alternatively, You can also set this at compile time by setting the `RHAI_AHASH_SEED`
-//! environment variable instead.
+//! # Example
 //!
-//! E.g. `env RHAI_AHASH_SEED ="[236,800,954,213]"`
+//! ```rust
+//! // Set the hashing seed to [1, 2, 3, 4]
+//! rhai::config::hashing::set_ahash_seed(Some([1, 2, 3, 4])).unwrap();
+//! ```
+//! Alternatively, set this at compile time via the `RHAI_AHASH_SEED` environment variable.
+//!
+//! # Example
+//!
+//! ```sh
+//! env RHAI_AHASH_SEED ="[236,800,954,213]"
+//! ```
 // [236,800,954,213], haha funny yume nikki reference epic uboachan face numberworld nexus moment 100
 
 use crate::config::hashing_env;
-use core::{
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+use std::{
     cell::UnsafeCell,
     marker::PhantomData,
+    mem,
     mem::MaybeUninit,
     panic::{RefUnwindSafe, UnwindSafe},
     sync::atomic::{AtomicBool, AtomicUsize, Ordering},
@@ -23,23 +35,25 @@ use core::{
 // what does this do?
 // so what this does is keep track of a global address in memory that acts as a global lock
 // i stole this from crossbeam so read their docs for more
+#[must_use]
 struct HokmaLock {
     lock: AtomicUsize,
 }
 
 impl HokmaLock {
+    #[inline(always)]
     pub const fn new() -> Self {
         Self {
             lock: AtomicUsize::new(0),
         }
     }
 
-    pub fn write(&'static self) -> WhenTheHokmaSupression {
+    pub fn write(&'static self) -> WhenTheHokmaSuppression {
         loop {
             let previous = self.lock.swap(1, Ordering::SeqCst);
 
             if previous != 1 {
-                return WhenTheHokmaSupression {
+                return WhenTheHokmaSuppression {
                     hokma: self,
                     state: previous,
                 };
@@ -48,21 +62,21 @@ impl HokmaLock {
     }
 }
 
-struct WhenTheHokmaSupression {
+struct WhenTheHokmaSuppression {
     hokma: &'static HokmaLock,
-
     state: usize,
 }
 
-impl WhenTheHokmaSupression {
+impl WhenTheHokmaSuppression {
+    #[inline]
     pub fn the_price_of_silence(self) {
         self.hokma.lock.store(self.state, Ordering::SeqCst);
-
-        core::mem::forget(self)
+        mem::forget(self)
     }
 }
 
-impl Drop for WhenTheHokmaSupression {
+impl Drop for WhenTheHokmaSuppression {
+    #[inline]
     fn drop(&mut self) {
         self.hokma
             .lock
@@ -70,6 +84,8 @@ impl Drop for WhenTheHokmaSupression {
     }
 }
 
+#[inline(always)]
+#[must_use]
 fn hokmalock(address: usize) -> &'static HokmaLock {
     const LEN: usize = 787;
     const LCK: HokmaLock = HokmaLock::new();
@@ -79,11 +95,12 @@ fn hokmalock(address: usize) -> &'static HokmaLock {
 }
 
 // Safety: lol, there is a reason its called "SusLock<T>"
+#[must_use]
 struct SusLock<T>
 where
     T: 'static + Copy,
 {
-    initalized: AtomicBool,
+    initialized: AtomicBool,
     data: UnsafeCell<MaybeUninit<T>>,
     _marker: PhantomData<T>,
 }
@@ -92,17 +109,19 @@ impl<T> SusLock<T>
 where
     T: 'static + Copy,
 {
+    #[inline]
     pub const fn new() -> SusLock<T> {
         SusLock {
-            initalized: AtomicBool::new(false),
+            initialized: AtomicBool::new(false),
             data: UnsafeCell::new(MaybeUninit::uninit()),
             _marker: PhantomData,
         }
     }
 
+    #[must_use]
     pub fn get(&self) -> Option<T> {
-        if self.initalized.load(Ordering::SeqCst) {
-            let hokma = hokmalock(unsafe { core::mem::transmute(self.data.get()) });
+        if self.initialized.load(Ordering::SeqCst) {
+            let hokma = hokmalock(unsafe { mem::transmute(self.data.get()) });
             // we forgo the optimistic read, because we don't really care
             let guard = hokma.write();
             let val = {
@@ -116,11 +135,12 @@ where
         }
     }
 
+    #[must_use]
     pub fn get_or_init(&self, f: impl FnOnce() -> T) -> Option<T> {
         let value = f();
-        if !self.initalized.load(Ordering::SeqCst) {
-            self.initalized.store(true, Ordering::SeqCst);
-            let hokma = hokmalock(unsafe { core::mem::transmute(self.data.get()) });
+        if !self.initialized.load(Ordering::SeqCst) {
+            self.initialized.store(true, Ordering::SeqCst);
+            let hokma = hokmalock(unsafe { mem::transmute(self.data.get()) });
             hokma.write();
             unsafe {
                 self.data.get().write(MaybeUninit::new(value));
@@ -131,7 +151,7 @@ where
     }
 
     pub fn set(&self, value: T) -> Result<(), T> {
-        if self.initalized.load(Ordering::SeqCst) {
+        if self.initialized.load(Ordering::SeqCst) {
             Err(value)
         } else {
             let _ = self.get_or_init(|| value);
@@ -148,8 +168,9 @@ impl<T> Drop for SusLock<T>
 where
     T: 'static + Copy,
 {
+    #[inline]
     fn drop(&mut self) {
-        if self.initalized.load(Ordering::SeqCst) {
+        if self.initialized.load(Ordering::SeqCst) {
             unsafe { (&mut *self.data.get()).assume_init_drop() };
         }
     }
@@ -157,27 +178,44 @@ where
 
 static AHASH_SEED: SusLock<Option<[u64; 4]>> = SusLock::new();
 
-// #[doc(cfg(feature = "stable_hash"))]
-/// Sets the Rhai Ahash seed. This is used to hash functions and the like.
+/// Set the hashing seed. This is used to hash functions etc.
 ///
-/// This is a global variable, and thus will affect every Rhai instance.
+/// This is a static global value and affects every Rhai instance.
 /// This should not be used _unless_ you know you need it.
 ///
-/// # Warnings
-/// - You can only call this function **ONCE** for the whole of your program execution.
-/// - You should gracefully handle the `Err(())`.
-/// - You **MUST** call this before **ANY** Rhai operation occurs (e.g. creating an [`Engine`]).
+/// # Warning
 ///
-/// # Errors
-/// This will error if the AHashSeed is already set.
+/// * You can only call this function **ONCE** for the entire duration of program execution.
+/// * You **MUST** call this before performing **ANY** Rhai operation (e.g. creating an [`Engine`]).
+///
+/// # Error
+///
+/// Returns an error containing the existing hashing seed if already set.
+///
+/// # Example
+///
+/// ```rust
+/// # use rhai::Engine;
+/// // Set the hashing seed to [1, 2, 3, 4]
+/// rhai::config::hashing::set_ahash_seed(Some([1, 2, 3, 4])).unwrap();
+///
+/// // Use Rhai AFTER setting the hashing seed
+/// let engine = Engine::new();
+/// ```
+#[inline(always)]
 pub fn set_ahash_seed(new_seed: Option<[u64; 4]>) -> Result<(), Option<[u64; 4]>> {
     AHASH_SEED.set(new_seed)
 }
 
-/// Gets the current Rhai Ahash Seed. If the seed is not yet defined, this will automatically set a seed.
-/// The default seed is not stable and may change between versions.
+/// Get the current hashing Seed.
+///
+/// If the seed is not yet defined, the `RHAI_AHASH_SEED` environment variable (if any) is used.
+///
+/// Otherwise, the hashing seed is randomized to protect against DOS attacks.
 ///
 /// See [`set_rhai_ahash_seed`] for more.
+#[inline]
+#[must_use]
 pub fn get_ahash_seed() -> Option<[u64; 4]> {
     AHASH_SEED.get_or_init(|| hashing_env::AHASH_SEED).flatten()
 }
diff --git a/src/config/hashing_env.rs b/src/config/hashing_env.rs
index ee2b35db..59930ad8 100644
--- a/src/config/hashing_env.rs
+++ b/src/config/hashing_env.rs
@@ -1,2 +1,3 @@
-// This file is automatically set during build time by build.rs and build.template.
+//! This file is automatically recreated during build time by `build.rs` from `build.template`.
+
 pub(crate) const AHASH_SEED: Option<[u64; 4]> = None;
diff --git a/src/config/mod.rs b/src/config/mod.rs
index db5448f6..35aac0af 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -1,4 +1,4 @@
-//! Contains Configuration for Rhai.
+//! Configuration for Rhai.
 
 pub mod hashing;
 mod hashing_env;
diff --git a/src/eval/chaining.rs b/src/eval/chaining.rs
index dbf40e3a..ecc40fc7 100644
--- a/src/eval/chaining.rs
+++ b/src/eval/chaining.rs
@@ -41,6 +41,7 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         this_ptr: &mut Option<&mut Dynamic>,
         target: &mut Target,
         root: (&str, Position),
@@ -49,7 +50,6 @@ impl Engine {
         rhs: &Expr,
         idx_values: &mut FnArgsVec<Dynamic>,
         chain_type: ChainType,
-        level: usize,
         new_val: &mut Option<(Dynamic, &OpAssignment)>,
     ) -> RhaiResultOf<(Dynamic, bool)> {
         let is_ref_mut = target.is_ref();
@@ -73,7 +73,7 @@ impl Engine {
                         if !parent_options.contains(ASTFlags::BREAK) =>
                     {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, _parent, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, _parent)?;
 
                         let idx_val = &mut idx_values.pop().unwrap();
                         let mut idx_val_for_setter = idx_val.clone();
@@ -82,14 +82,14 @@ impl Engine {
 
                         let (try_setter, result) = {
                             let mut obj = self.get_indexed_mut(
-                                global, caches, lib, target, idx_val, idx_pos, false, true, level,
+                                global, caches, lib, level, target, idx_val, idx_pos, false, true,
                             )?;
                             let is_obj_temp_val = obj.is_temp_value();
                             let obj_ptr = &mut obj;
 
                             match self.eval_dot_index_chain_helper(
-                                global, caches, lib, this_ptr, obj_ptr, root, rhs, *options,
-                                &x.rhs, idx_values, rhs_chain, level, new_val,
+                                global, caches, lib, level, this_ptr, obj_ptr, root, rhs, *options,
+                                &x.rhs, idx_values, rhs_chain, new_val,
                             ) {
                                 Ok((result, true)) if is_obj_temp_val => {
                                     (Some(obj.take_or_clone()), (result, true))
@@ -104,7 +104,7 @@ impl Engine {
                             let idx = &mut idx_val_for_setter;
                             let new_val = &mut new_val;
                             self.call_indexer_set(
-                                global, caches, lib, target, idx, new_val, is_ref_mut, level,
+                                global, caches, lib, level, target, idx, new_val, is_ref_mut,
                             )
                             .or_else(|e| match *e {
                                 ERR::ErrorIndexingType(..) => Ok((Dynamic::UNIT, false)),
@@ -117,19 +117,19 @@ impl Engine {
                     // xxx[rhs] op= new_val
                     _ if new_val.is_some() => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, _parent, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, _parent)?;
 
                         let (new_val, op_info) = new_val.take().expect("`Some`");
                         let idx_val = &mut idx_values.pop().unwrap();
                         let idx = &mut idx_val.clone();
 
                         let try_setter = match self.get_indexed_mut(
-                            global, caches, lib, target, idx, pos, true, false, level,
+                            global, caches, lib, level, target, idx, pos, true, false,
                         ) {
                             // Indexed value is not a temp value - update directly
                             Ok(ref mut obj_ptr) => {
                                 self.eval_op_assignment(
-                                    global, caches, lib, op_info, obj_ptr, root, new_val, level,
+                                    global, caches, lib, level, op_info, obj_ptr, root, new_val,
                                 )?;
                                 self.check_data_size(obj_ptr, op_info.pos)?;
                                 None
@@ -148,13 +148,13 @@ impl Engine {
 
                                 // Call the index getter to get the current value
                                 if let Ok(val) =
-                                    self.call_indexer_get(global, caches, lib, target, idx, level)
+                                    self.call_indexer_get(global, caches, lib, level, target, idx)
                                 {
                                     let mut val = val.into();
                                     // Run the op-assignment
                                     self.eval_op_assignment(
-                                        global, caches, lib, op_info, &mut val, root, new_val,
-                                        level,
+                                        global, caches, lib, level, op_info, &mut val, root,
+                                        new_val,
                                     )?;
                                     // Replace new value
                                     new_val = val.take_or_clone();
@@ -166,7 +166,7 @@ impl Engine {
                             let new_val = &mut new_val;
 
                             self.call_indexer_set(
-                                global, caches, lib, target, idx_val, new_val, is_ref_mut, level,
+                                global, caches, lib, level, target, idx_val, new_val, is_ref_mut,
                             )?;
                         }
 
@@ -175,12 +175,12 @@ impl Engine {
                     // xxx[rhs]
                     _ => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, _parent, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, _parent)?;
 
                         let idx_val = &mut idx_values.pop().unwrap();
 
                         self.get_indexed_mut(
-                            global, caches, lib, target, idx_val, pos, false, true, level,
+                            global, caches, lib, level, target, idx_val, pos, false, true,
                         )
                         .map(|v| (v.take_or_clone(), false))
                     }
@@ -198,8 +198,9 @@ impl Engine {
                     // xxx.fn_name(arg_expr_list)
                     Expr::MethodCall(x, pos) if !x.is_qualified() && new_val.is_none() => {
                         #[cfg(feature = "debugging")]
-                        let reset_debugger =
-                            self.run_debugger_with_reset(scope, global, lib, this_ptr, rhs, level)?;
+                        let reset_debugger = self.run_debugger_with_reset(
+                            global, caches, lib, level, scope, this_ptr, rhs,
+                        )?;
 
                         let crate::ast::FnCallExpr {
                             name, hashes, args, ..
@@ -210,8 +211,8 @@ impl Engine {
                         let pos1 = args.get(0).map_or(Position::NONE, Expr::position);
 
                         let result = self.make_method_call(
-                            global, caches, lib, name, *hashes, target, call_args, pos1, *pos,
-                            level,
+                            global, caches, lib, level, name, *hashes, target, call_args, pos1,
+                            *pos,
                         );
 
                         idx_values.truncate(offset);
@@ -232,16 +233,16 @@ impl Engine {
                     // {xxx:map}.id op= ???
                     Expr::Property(x, pos) if target.is::<crate::Map>() && new_val.is_some() => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, rhs, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, rhs)?;
 
                         let index = &mut x.2.clone().into();
                         let (new_val, op_info) = new_val.take().expect("`Some`");
                         {
                             let val_target = &mut self.get_indexed_mut(
-                                global, caches, lib, target, index, *pos, true, false, level,
+                                global, caches, lib, level, target, index, *pos, true, false,
                             )?;
                             self.eval_op_assignment(
-                                global, caches, lib, op_info, val_target, root, new_val, level,
+                                global, caches, lib, level, op_info, val_target, root, new_val,
                             )?;
                         }
                         self.check_data_size(target.source(), op_info.pos)?;
@@ -250,18 +251,18 @@ impl Engine {
                     // {xxx:map}.id
                     Expr::Property(x, pos) if target.is::<crate::Map>() => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, rhs, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, rhs)?;
 
                         let index = &mut x.2.clone().into();
                         let val = self.get_indexed_mut(
-                            global, caches, lib, target, index, *pos, false, false, level,
+                            global, caches, lib, level, target, index, *pos, false, false,
                         )?;
                         Ok((val.take_or_clone(), false))
                     }
                     // xxx.id op= ???
                     Expr::Property(x, pos) if new_val.is_some() => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, rhs, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, rhs)?;
 
                         let ((getter, hash_get), (setter, hash_set), name) = &**x;
                         let (mut new_val, op_info) = new_val.take().expect("`Some`");
@@ -269,16 +270,16 @@ impl Engine {
                         if op_info.is_op_assignment() {
                             let args = &mut [target.as_mut()];
                             let (mut orig_val, ..) = self
-                                .call_native_fn(
-                                    global, caches, lib, getter, *hash_get, args, is_ref_mut,
-                                    false, *pos, level,
+                                .exec_native_fn_call(
+                                    global, caches, lib, level, getter, None, *hash_get, args,
+                                    is_ref_mut, *pos,
                                 )
                                 .or_else(|err| match *err {
                                     // Try an indexer if property does not exist
                                     ERR::ErrorDotExpr(..) => {
                                         let mut prop = name.into();
                                         self.call_indexer_get(
-                                            global, caches, lib, target, &mut prop, level,
+                                            global, caches, lib, level, target, &mut prop,
                                         )
                                         .map(|r| (r, false))
                                         .map_err(|e| {
@@ -295,7 +296,7 @@ impl Engine {
                                 let orig_val = &mut (&mut orig_val).into();
 
                                 self.eval_op_assignment(
-                                    global, caches, lib, op_info, orig_val, root, new_val, level,
+                                    global, caches, lib, level, op_info, orig_val, root, new_val,
                                 )?;
                             }
 
@@ -303,9 +304,9 @@ impl Engine {
                         }
 
                         let args = &mut [target.as_mut(), &mut new_val];
-                        self.call_native_fn(
-                            global, caches, lib, setter, *hash_set, args, is_ref_mut, false, *pos,
-                            level,
+                        self.exec_native_fn_call(
+                            global, caches, lib, level, setter, None, *hash_set, args, is_ref_mut,
+                            *pos,
                         )
                         .or_else(|err| match *err {
                             // Try an indexer if property does not exist
@@ -313,7 +314,7 @@ impl Engine {
                                 let idx = &mut name.into();
                                 let new_val = &mut new_val;
                                 self.call_indexer_set(
-                                    global, caches, lib, target, idx, new_val, is_ref_mut, level,
+                                    global, caches, lib, level, target, idx, new_val, is_ref_mut,
                                 )
                                 .map_err(|e| match *e {
                                     ERR::ErrorIndexingType(..) => err,
@@ -326,13 +327,13 @@ impl Engine {
                     // xxx.id
                     Expr::Property(x, pos) => {
                         #[cfg(feature = "debugging")]
-                        self.run_debugger(scope, global, lib, this_ptr, rhs, level)?;
+                        self.run_debugger(global, caches, lib, level, scope, this_ptr, rhs)?;
 
                         let ((getter, hash_get), _, name) = &**x;
                         let args = &mut [target.as_mut()];
-                        self.call_native_fn(
-                            global, caches, lib, getter, *hash_get, args, is_ref_mut, false, *pos,
-                            level,
+                        self.exec_native_fn_call(
+                            global, caches, lib, level, getter, None, *hash_get, args, is_ref_mut,
+                            *pos,
                         )
                         .map_or_else(
                             |err| match *err {
@@ -340,7 +341,7 @@ impl Engine {
                                 ERR::ErrorDotExpr(..) => {
                                     let mut prop = name.into();
                                     self.call_indexer_get(
-                                        global, caches, lib, target, &mut prop, level,
+                                        global, caches, lib, level, target, &mut prop,
                                     )
                                     .map(|r| (r, false))
                                     .map_err(|e| match *e {
@@ -363,18 +364,20 @@ impl Engine {
                         let val_target = &mut match x.lhs {
                             Expr::Property(ref p, pos) => {
                                 #[cfg(feature = "debugging")]
-                                self.run_debugger(scope, global, lib, this_ptr, _node, level)?;
+                                self.run_debugger(
+                                    global, caches, lib, level, scope, this_ptr, _node,
+                                )?;
 
                                 let index = &mut p.2.clone().into();
                                 self.get_indexed_mut(
-                                    global, caches, lib, target, index, pos, false, true, level,
+                                    global, caches, lib, level, target, index, pos, false, true,
                                 )?
                             }
                             // {xxx:map}.fn_name(arg_expr_list)[expr] | {xxx:map}.fn_name(arg_expr_list).expr
                             Expr::MethodCall(ref x, pos) if !x.is_qualified() => {
                                 #[cfg(feature = "debugging")]
                                 let reset_debugger = self.run_debugger_with_reset(
-                                    scope, global, lib, this_ptr, _node, level,
+                                    global, caches, lib, level, scope, this_ptr, _node,
                                 )?;
 
                                 let crate::ast::FnCallExpr {
@@ -386,8 +389,8 @@ impl Engine {
                                 let pos1 = args.get(0).map_or(Position::NONE, Expr::position);
 
                                 let result = self.make_method_call(
-                                    global, caches, lib, name, *hashes, target, call_args, pos1,
-                                    pos, level,
+                                    global, caches, lib, level, name, *hashes, target, call_args,
+                                    pos1, pos,
                                 );
 
                                 idx_values.truncate(offset);
@@ -407,8 +410,8 @@ impl Engine {
                         let rhs_chain = rhs.into();
 
                         self.eval_dot_index_chain_helper(
-                            global, caches, lib, this_ptr, val_target, root, rhs, *options, &x.rhs,
-                            idx_values, rhs_chain, level, new_val,
+                            global, caches, lib, level, this_ptr, val_target, root, rhs, *options,
+                            &x.rhs, idx_values, rhs_chain, new_val,
                         )
                         .map_err(|err| err.fill_position(*x_pos))
                     }
@@ -420,7 +423,9 @@ impl Engine {
                             // xxx.prop[expr] | xxx.prop.expr
                             Expr::Property(ref p, pos) => {
                                 #[cfg(feature = "debugging")]
-                                self.run_debugger(scope, global, lib, this_ptr, _node, level)?;
+                                self.run_debugger(
+                                    global, caches, lib, level, scope, this_ptr, _node,
+                                )?;
 
                                 let ((getter, hash_get), (setter, hash_set), name) = &**p;
                                 let rhs_chain = rhs.into();
@@ -429,16 +434,16 @@ impl Engine {
 
                                 // Assume getters are always pure
                                 let (mut val, ..) = self
-                                    .call_native_fn(
-                                        global, caches, lib, getter, *hash_get, args, is_ref_mut,
-                                        false, pos, level,
+                                    .exec_native_fn_call(
+                                        global, caches, lib, level, getter, None, *hash_get, args,
+                                        is_ref_mut, pos,
                                     )
                                     .or_else(|err| match *err {
                                         // Try an indexer if property does not exist
                                         ERR::ErrorDotExpr(..) => {
                                             let mut prop = name.into();
                                             self.call_indexer_get(
-                                                global, caches, lib, target, &mut prop, level,
+                                                global, caches, lib, level, target, &mut prop,
                                             )
                                             .map(|r| (r, false))
                                             .map_err(
@@ -455,8 +460,8 @@ impl Engine {
 
                                 let (result, may_be_changed) = self
                                     .eval_dot_index_chain_helper(
-                                        global, caches, lib, this_ptr, val, root, rhs, *options,
-                                        &x.rhs, idx_values, rhs_chain, level, new_val,
+                                        global, caches, lib, level, this_ptr, val, root, rhs,
+                                        *options, &x.rhs, idx_values, rhs_chain, new_val,
                                     )
                                     .map_err(|err| err.fill_position(*x_pos))?;
 
@@ -465,9 +470,9 @@ impl Engine {
                                     // Re-use args because the first &mut parameter will not be consumed
                                     let mut arg_values = [target.as_mut(), val.as_mut()];
                                     let args = &mut arg_values;
-                                    self.call_native_fn(
-                                        global, caches, lib, setter, *hash_set, args, is_ref_mut,
-                                        false, pos, level,
+                                    self.exec_native_fn_call(
+                                        global, caches, lib, level, setter, None, *hash_set, args,
+                                        is_ref_mut, pos,
                                     )
                                     .or_else(
                                         |err| match *err {
@@ -476,8 +481,8 @@ impl Engine {
                                                 let idx = &mut name.into();
                                                 let new_val = val;
                                                 self.call_indexer_set(
-                                                    global, caches, lib, target, idx, new_val,
-                                                    is_ref_mut, level,
+                                                    global, caches, lib, level, target, idx,
+                                                    new_val, is_ref_mut,
                                                 )
                                                 .or_else(|e| match *e {
                                                     // If there is no setter, no need to feed it
@@ -499,7 +504,7 @@ impl Engine {
                             Expr::MethodCall(ref f, pos) if !f.is_qualified() => {
                                 #[cfg(feature = "debugging")]
                                 let reset_debugger = self.run_debugger_with_reset(
-                                    scope, global, lib, this_ptr, _node, level,
+                                    global, caches, lib, level, scope, this_ptr, _node,
                                 )?;
 
                                 let crate::ast::FnCallExpr {
@@ -512,8 +517,8 @@ impl Engine {
                                 let pos1 = args.get(0).map_or(Position::NONE, Expr::position);
 
                                 let result = self.make_method_call(
-                                    global, caches, lib, name, *hashes, target, call_args, pos1,
-                                    pos, level,
+                                    global, caches, lib, level, name, *hashes, target, call_args,
+                                    pos1, pos,
                                 );
 
                                 idx_values.truncate(offset);
@@ -525,8 +530,8 @@ impl Engine {
                                 let val = &mut val.into();
 
                                 self.eval_dot_index_chain_helper(
-                                    global, caches, lib, this_ptr, val, root, rhs, *options,
-                                    &x.rhs, idx_values, rhs_chain, level, new_val,
+                                    global, caches, lib, level, this_ptr, val, root, rhs, *options,
+                                    &x.rhs, idx_values, rhs_chain, new_val,
                                 )
                                 .map_err(|err| err.fill_position(pos))
                             }
@@ -548,13 +553,13 @@ impl Engine {
     /// Evaluate a dot/index chain.
     pub(crate) fn eval_dot_index_chain(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         expr: &Expr,
-        level: usize,
         new_val: &mut Option<(Dynamic, &OpAssignment)>,
     ) -> RhaiResult {
         let chain_type = ChainType::from(expr);
@@ -592,8 +597,8 @@ impl Engine {
             // All other patterns - evaluate the arguments chain
             _ => {
                 self.eval_dot_index_chain_arguments(
-                    scope, global, caches, lib, this_ptr, rhs, options, chain_type, idx_values,
-                    level,
+                    global, caches, lib, level, scope, this_ptr, rhs, options, chain_type,
+                    idx_values,
                 )?;
             }
         }
@@ -602,18 +607,18 @@ impl Engine {
             // id.??? or id[???]
             Expr::Variable(x, .., var_pos) => {
                 #[cfg(feature = "debugging")]
-                self.run_debugger(scope, global, lib, this_ptr, lhs, level)?;
+                self.run_debugger(global, caches, lib, level, scope, this_ptr, lhs)?;
                 self.track_operation(global, *var_pos)?;
 
                 let (mut target, ..) =
-                    self.search_namespace(scope, global, lib, this_ptr, lhs, level)?;
+                    self.search_namespace(global, caches, lib, level, scope, this_ptr, lhs)?;
 
                 let obj_ptr = &mut target;
                 let root = (x.3.as_str(), *var_pos);
 
                 self.eval_dot_index_chain_helper(
-                    global, caches, lib, &mut None, obj_ptr, root, expr, options, rhs, idx_values,
-                    chain_type, level, new_val,
+                    global, caches, lib, level, &mut None, obj_ptr, root, expr, options, rhs,
+                    idx_values, chain_type, new_val,
                 )
             }
             // {expr}.??? = ??? or {expr}[???] = ???
@@ -621,14 +626,14 @@ impl Engine {
             // {expr}.??? or {expr}[???]
             expr => {
                 let value = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, expr, level)?
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, expr)?
                     .flatten();
                 let obj_ptr = &mut value.into();
                 let root = ("", expr.start_position());
 
                 self.eval_dot_index_chain_helper(
-                    global, caches, lib, this_ptr, obj_ptr, root, expr, options, rhs, idx_values,
-                    chain_type, level, new_val,
+                    global, caches, lib, level, this_ptr, obj_ptr, root, expr, options, rhs,
+                    idx_values, chain_type, new_val,
                 )
             }
         }
@@ -639,16 +644,16 @@ impl Engine {
     /// Evaluate a chain of indexes and store the results in a [`FnArgsVec`].
     fn eval_dot_index_chain_arguments(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         expr: &Expr,
         parent_options: ASTFlags,
         parent_chain_type: ChainType,
         idx_values: &mut FnArgsVec<Dynamic>,
-        level: usize,
     ) -> RhaiResultOf<()> {
         self.track_operation(global, expr.position())?;
 
@@ -659,7 +664,7 @@ impl Engine {
             {
                 for arg_expr in &x.args {
                     idx_values.push(
-                        self.get_arg_value(scope, global, caches, lib, this_ptr, arg_expr, level)?
+                        self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg_expr)?
                             .0
                             .flatten(),
                     );
@@ -694,7 +699,7 @@ impl Engine {
                         for arg_expr in &x.args {
                             _arg_values.push(
                                 self.get_arg_value(
-                                    scope, global, caches, lib, this_ptr, arg_expr, level,
+                                    global, caches, lib, level, scope, this_ptr, arg_expr,
                                 )?
                                 .0
                                 .flatten(),
@@ -712,7 +717,7 @@ impl Engine {
                     #[cfg(not(feature = "no_index"))]
                     _ if parent_chain_type == ChainType::Indexing => {
                         _arg_values.push(
-                            self.eval_expr(scope, global, caches, lib, this_ptr, lhs, level)?
+                            self.eval_expr(global, caches, lib, level, scope, this_ptr, lhs)?
                                 .flatten(),
                         );
                     }
@@ -723,8 +728,8 @@ impl Engine {
                 let chain_type = expr.into();
 
                 self.eval_dot_index_chain_arguments(
-                    scope, global, caches, lib, this_ptr, rhs, *options, chain_type, idx_values,
-                    level,
+                    global, caches, lib, level, scope, this_ptr, rhs, *options, chain_type,
+                    idx_values,
                 )?;
 
                 if !_arg_values.is_empty() {
@@ -738,7 +743,7 @@ impl Engine {
             }
             #[cfg(not(feature = "no_index"))]
             _ if parent_chain_type == ChainType::Indexing => idx_values.push(
-                self.eval_expr(scope, global, caches, lib, this_ptr, expr, level)?
+                self.eval_expr(global, caches, lib, level, scope, this_ptr, expr)?
                     .flatten(),
             ),
             _ => unreachable!("unknown chained expression: {:?}", expr),
@@ -754,9 +759,9 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         target: &mut Dynamic,
         idx: &mut Dynamic,
-        level: usize,
     ) -> RhaiResultOf<Dynamic> {
         let args = &mut [target, idx];
         let hash = global.hash_idx_get();
@@ -764,8 +769,8 @@ impl Engine {
         let pos = Position::NONE;
         let level = level + 1;
 
-        self.call_native_fn(
-            global, caches, lib, fn_name, hash, args, true, false, pos, level,
+        self.exec_native_fn_call(
+            global, caches, lib, level, fn_name, None, hash, args, true, pos,
         )
         .map(|(r, ..)| r)
     }
@@ -777,11 +782,11 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         target: &mut Dynamic,
         idx: &mut Dynamic,
         new_val: &mut Dynamic,
         is_ref_mut: bool,
-        level: usize,
     ) -> RhaiResultOf<(Dynamic, bool)> {
         let hash = global.hash_idx_set();
         let args = &mut [target, idx, new_val];
@@ -789,8 +794,8 @@ impl Engine {
         let pos = Position::NONE;
         let level = level + 1;
 
-        self.call_native_fn(
-            global, caches, lib, fn_name, hash, args, is_ref_mut, false, pos, level,
+        self.exec_native_fn_call(
+            global, caches, lib, level, fn_name, None, hash, args, is_ref_mut, pos,
         )
     }
 
@@ -801,12 +806,12 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         target: &'t mut Dynamic,
         idx: &mut Dynamic,
         idx_pos: Position,
         _add_if_not_found: bool,
         use_indexers: bool,
-        level: usize,
     ) -> RhaiResultOf<Target<'t>> {
         self.track_operation(global, Position::NONE)?;
 
@@ -1010,7 +1015,7 @@ impl Engine {
             }
 
             _ if use_indexers => self
-                .call_indexer_get(global, caches, lib, target, idx, level)
+                .call_indexer_get(global, caches, lib, level, target, idx)
                 .map(Into::into),
 
             _ => Err(ERR::ErrorIndexingType(
diff --git a/src/eval/debugger.rs b/src/eval/debugger.rs
index f87e4a81..9b516fdf 100644
--- a/src/eval/debugger.rs
+++ b/src/eval/debugger.rs
@@ -1,7 +1,7 @@
 //! Module defining the debugging interface.
 #![cfg(feature = "debugging")]
 
-use super::{EvalContext, GlobalRuntimeState};
+use super::{Caches, EvalContext, GlobalRuntimeState};
 use crate::ast::{ASTNode, Expr, Stmt};
 use crate::{
     Dynamic, Engine, EvalAltResult, ImmutableString, Module, Position, RhaiResultOf, Scope,
@@ -411,16 +411,17 @@ impl Engine {
     #[inline(always)]
     pub(crate) fn run_debugger<'a>(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         node: impl Into<ASTNode<'a>>,
-        level: usize,
     ) -> RhaiResultOf<()> {
         if self.debugger.is_some() {
             if let Some(cmd) =
-                self.run_debugger_with_reset_raw(scope, global, lib, this_ptr, node, level)?
+                self.run_debugger_with_reset_raw(global, caches, lib, level, scope, this_ptr, node)?
             {
                 global.debugger.status = cmd;
             }
@@ -430,41 +431,43 @@ impl Engine {
     }
     /// Run the debugger callback if there is a debugging interface registered.
     ///
-    /// Returns `Some` if the debugger needs to be reactivated at the end of the block, statement or
+    /// Returns [`Some`] if the debugger needs to be reactivated at the end of the block, statement or
     /// function call.
     ///
     /// It is up to the [`Engine`] to reactivate the debugger.
     #[inline(always)]
     pub(crate) fn run_debugger_with_reset<'a>(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         node: impl Into<ASTNode<'a>>,
-        level: usize,
     ) -> RhaiResultOf<Option<DebuggerStatus>> {
         if self.debugger.is_some() {
-            self.run_debugger_with_reset_raw(scope, global, lib, this_ptr, node, level)
+            self.run_debugger_with_reset_raw(global, caches, lib, level, scope, this_ptr, node)
         } else {
             Ok(None)
         }
     }
     /// Run the debugger callback.
     ///
-    /// Returns `Some` if the debugger needs to be reactivated at the end of the block, statement or
+    /// Returns [`Some`] if the debugger needs to be reactivated at the end of the block, statement or
     /// function call.
     ///
     /// It is up to the [`Engine`] to reactivate the debugger.
     #[inline]
     pub(crate) fn run_debugger_with_reset_raw<'a>(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         node: impl Into<ASTNode<'a>>,
-        level: usize,
     ) -> RhaiResultOf<Option<DebuggerStatus>> {
         let node = node.into();
 
@@ -494,28 +497,30 @@ impl Engine {
             },
         };
 
-        self.run_debugger_raw(scope, global, lib, this_ptr, node, event, level)
+        self.run_debugger_raw(global, caches, lib, level, scope, this_ptr, node, event)
     }
     /// Run the debugger callback unconditionally.
     ///
-    /// Returns `Some` if the debugger needs to be reactivated at the end of the block, statement or
+    /// Returns [`Some`] if the debugger needs to be reactivated at the end of the block, statement or
     /// function call.
     ///
     /// It is up to the [`Engine`] to reactivate the debugger.
     #[inline]
     pub(crate) fn run_debugger_raw<'a>(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         node: ASTNode<'a>,
         event: DebuggerEvent,
-        level: usize,
     ) -> Result<Option<DebuggerStatus>, Box<crate::EvalAltResult>> {
         let src = global.source_raw().cloned();
         let src = src.as_ref().map(|s| s.as_str());
-        let context = crate::EvalContext::new(self, scope, global, None, lib, this_ptr, level);
+        let context =
+            crate::EvalContext::new(self, global, Some(caches), lib, level, scope, this_ptr);
 
         if let Some((.., ref on_debugger)) = self.debugger {
             let command = on_debugger(context, event, node, src, node.position())?;
diff --git a/src/eval/eval_context.rs b/src/eval/eval_context.rs
index b1185a39..172720cd 100644
--- a/src/eval/eval_context.rs
+++ b/src/eval/eval_context.rs
@@ -31,12 +31,12 @@ impl<'a, 's, 'ps, 'g, 'pg, 'c, 'pc, 't, 'pt> EvalContext<'a, 's, 'ps, 'g, 'pg, '
     #[must_use]
     pub fn new(
         engine: &'a Engine,
-        scope: &'s mut Scope<'ps>,
         global: &'g mut GlobalRuntimeState<'pg>,
         caches: Option<&'c mut Caches<'pc>>,
         lib: &'a [&'a Module],
-        this_ptr: &'t mut Option<&'pt mut Dynamic>,
         level: usize,
+        scope: &'s mut Scope<'ps>,
+        this_ptr: &'t mut Option<&'pt mut Dynamic>,
     ) -> Self {
         Self {
             engine,
@@ -182,23 +182,23 @@ impl<'a, 's, 'ps, 'g, 'pg, 'c, 'pc, 't, 'pt> EvalContext<'a, 's, 'ps, 'g, 'pg, '
 
         match expr {
             crate::ast::Expr::Stmt(statements) => self.engine.eval_stmt_block(
-                self.scope,
                 self.global,
                 caches,
                 self.lib,
+                self.level,
+                self.scope,
                 self.this_ptr,
                 statements,
                 rewind_scope,
-                self.level,
             ),
             _ => self.engine.eval_expr(
-                self.scope,
                 self.global,
                 caches,
                 self.lib,
+                self.level,
+                self.scope,
                 self.this_ptr,
                 expr,
-                self.level,
             ),
         }
     }
diff --git a/src/eval/expr.rs b/src/eval/expr.rs
index 5afd07d9..0a9558da 100644
--- a/src/eval/expr.rs
+++ b/src/eval/expr.rs
@@ -1,9 +1,8 @@
 //! Module defining functions for evaluating an expression.
 
 use super::{Caches, EvalContext, GlobalRuntimeState, Target};
-use crate::ast::{Expr, FnCallExpr, OpAssignment};
+use crate::ast::{Expr, OpAssignment};
 use crate::engine::{KEYWORD_THIS, OP_CONCAT};
-use crate::func::get_builtin_binary_op_fn;
 use crate::types::dynamic::AccessMode;
 use crate::{Dynamic, Engine, Module, Position, RhaiResult, RhaiResultOf, Scope, ERR};
 use std::num::NonZeroUsize;
@@ -50,25 +49,28 @@ impl Engine {
     /// depending on whether the variable name is namespace-qualified.
     pub(crate) fn search_namespace<'s>(
         &self,
-        scope: &'s mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &'s mut Scope,
         this_ptr: &'s mut Option<&mut Dynamic>,
         expr: &Expr,
-        level: usize,
     ) -> RhaiResultOf<(Target<'s>, Position)> {
         match expr {
             Expr::Variable(_, Some(_), _) => {
-                self.search_scope_only(scope, global, lib, this_ptr, expr, level)
+                self.search_scope_only(global, caches, lib, level, scope, this_ptr, expr)
             }
             Expr::Variable(v, None, _var_pos) => match &**v {
                 // Normal variable access
                 #[cfg(not(feature = "no_module"))]
                 (_, ns, ..) if ns.is_empty() => {
-                    self.search_scope_only(scope, global, lib, this_ptr, expr, level)
+                    self.search_scope_only(global, caches, lib, level, scope, this_ptr, expr)
                 }
                 #[cfg(feature = "no_module")]
-                (_, (), ..) => self.search_scope_only(scope, global, lib, this_ptr, expr, level),
+                (_, (), ..) => {
+                    self.search_scope_only(global, caches, lib, level, scope, this_ptr, expr)
+                }
 
                 // Qualified variable access
                 #[cfg(not(feature = "no_module"))]
@@ -133,12 +135,13 @@ impl Engine {
     /// Panics if `expr` is not [`Expr::Variable`].
     pub(crate) fn search_scope_only<'s>(
         &self,
-        scope: &'s mut Scope,
         global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &'s mut Scope,
         this_ptr: &'s mut Option<&mut Dynamic>,
         expr: &Expr,
-        level: usize,
     ) -> RhaiResultOf<(Target<'s>, Position)> {
         // Make sure that the pointer indirection is taken only when absolutely necessary.
 
@@ -170,7 +173,7 @@ impl Engine {
 
         // Check the variable resolver, if any
         if let Some(ref resolve_var) = self.resolve_var {
-            let context = EvalContext::new(self, scope, global, None, lib, this_ptr, level);
+            let context = EvalContext::new(self, global, Some(caches), lib, level, scope, this_ptr);
             let var_name = expr.get_variable_name(true).expect("`Expr::Variable`");
             match resolve_var(var_name, index, context) {
                 Ok(Some(mut result)) => {
@@ -206,98 +209,6 @@ impl Engine {
         Ok((val.into(), var_pos))
     }
 
-    /// Evaluate a function call expression.
-    pub(crate) fn eval_fn_call_expr(
-        &self,
-        scope: &mut Scope,
-        global: &mut GlobalRuntimeState,
-        caches: &mut Caches,
-        lib: &[&Module],
-        this_ptr: &mut Option<&mut Dynamic>,
-        expr: &FnCallExpr,
-        pos: Position,
-        level: usize,
-    ) -> RhaiResult {
-        let FnCallExpr {
-            name,
-            hashes,
-            args,
-            operator_token,
-            #[cfg(not(feature = "no_function"))]
-            can_be_script,
-            ..
-        } = expr;
-
-        #[cfg(not(feature = "no_function"))]
-        let native = !can_be_script;
-        #[cfg(feature = "no_function")]
-        let native = true;
-
-        // Short-circuit native binary operator call if under Fast Operators mode
-        if operator_token.is_some() && self.fast_operators() && args.len() == 2 {
-            let mut lhs = self
-                .get_arg_value(scope, global, caches, lib, this_ptr, &args[0], level)?
-                .0
-                .flatten();
-
-            let mut rhs = self
-                .get_arg_value(scope, global, caches, lib, this_ptr, &args[1], level)?
-                .0
-                .flatten();
-
-            let operands = &mut [&mut lhs, &mut rhs];
-
-            if let Some(func) =
-                get_builtin_binary_op_fn(operator_token.as_ref().unwrap(), operands[0], operands[1])
-            {
-                // Built-in found
-                let context = (self, name.as_str(), None, &*global, lib, pos, level + 1).into();
-                return func(context, operands);
-            }
-
-            return self
-                .exec_fn_call(
-                    None, global, caches, lib, name, native, *hashes, operands, false, false, pos,
-                    level,
-                )
-                .map(|(v, ..)| v);
-        }
-
-        #[cfg(not(feature = "no_module"))]
-        if !expr.namespace.is_empty() {
-            // Qualified function call
-            let hash = hashes.native;
-            let namespace = &expr.namespace;
-
-            return self.make_qualified_function_call(
-                scope, global, caches, lib, this_ptr, namespace, name, args, hash, pos, level,
-            );
-        }
-
-        // Normal function call
-        let (first_arg, args) = args.split_first().map_or_else(
-            || (None, args.as_ref()),
-            |(first, rest)| (Some(first), rest),
-        );
-
-        self.make_function_call(
-            scope,
-            global,
-            caches,
-            lib,
-            this_ptr,
-            name,
-            native,
-            first_arg,
-            args,
-            *hashes,
-            expr.capture_parent_scope,
-            expr.operator_token.as_ref(),
-            pos,
-            level,
-        )
-    }
-
     /// Evaluate an expression.
     //
     // # Implementation Notes
@@ -308,28 +219,28 @@ impl Engine {
     // Errors that are not recoverable, such as system errors or safety errors, can use `?`.
     pub(crate) fn eval_expr(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         expr: &Expr,
-        level: usize,
     ) -> RhaiResult {
         // Coded this way for better branch prediction.
         // Popular branches are lifted out of the `match` statement into their own branches.
 
         // Function calls should account for a relatively larger portion of expressions because
         // binary operators are also function calls.
-        if let Expr::FnCall(x, ..) = expr {
+        if let Expr::FnCall(x, pos) = expr {
             #[cfg(feature = "debugging")]
             let reset_debugger =
-                self.run_debugger_with_reset(scope, global, lib, this_ptr, expr, level)?;
+                self.run_debugger_with_reset(global, caches, lib, level, scope, this_ptr, expr)?;
 
             self.track_operation(global, expr.position())?;
 
             let result =
-                self.eval_fn_call_expr(scope, global, caches, lib, this_ptr, x, x.pos, level);
+                self.eval_fn_call_expr(global, caches, lib, level, scope, this_ptr, x, *pos);
 
             #[cfg(feature = "debugging")]
             global.debugger.reset_status(reset_debugger);
@@ -342,7 +253,7 @@ impl Engine {
         // will cost more than the mis-predicted `match` branch.
         if let Expr::Variable(x, index, var_pos) = expr {
             #[cfg(feature = "debugging")]
-            self.run_debugger(scope, global, lib, this_ptr, expr, level)?;
+            self.run_debugger(global, caches, lib, level, scope, this_ptr, expr)?;
 
             self.track_operation(global, expr.position())?;
 
@@ -352,14 +263,14 @@ impl Engine {
                     .cloned()
                     .ok_or_else(|| ERR::ErrorUnboundThis(*var_pos).into())
             } else {
-                self.search_namespace(scope, global, lib, this_ptr, expr, level)
+                self.search_namespace(global, caches, lib, level, scope, this_ptr, expr)
                     .map(|(val, ..)| val.take_or_clone())
             };
         }
 
         #[cfg(feature = "debugging")]
         let reset_debugger =
-            self.run_debugger_with_reset(scope, global, lib, this_ptr, expr, level)?;
+            self.run_debugger_with_reset(global, caches, lib, level, scope, this_ptr, expr)?;
 
         self.track_operation(global, expr.position())?;
 
@@ -386,12 +297,12 @@ impl Engine {
                     .iter()
                     .try_for_each(|expr| {
                         let item =
-                            self.eval_expr(scope, global, caches, lib, this_ptr, expr, level)?;
+                            self.eval_expr(global, caches, lib, level, scope, this_ptr, expr)?;
 
                         op_info.pos = expr.start_position();
 
                         self.eval_op_assignment(
-                            global, caches, lib, &op_info, target, root, item, level,
+                            global, caches, lib, level, &op_info, target, root, item,
                         )
                     })
                     .map(|_| concat.take_or_clone());
@@ -409,7 +320,7 @@ impl Engine {
                         crate::Array::with_capacity(x.len()),
                         |mut array, item_expr| {
                             let value = self
-                                .eval_expr(scope, global, caches, lib, this_ptr, item_expr, level)?
+                                .eval_expr(global, caches, lib, level, scope, this_ptr, item_expr)?
                                 .flatten();
 
                             #[cfg(not(feature = "unchecked"))]
@@ -441,7 +352,7 @@ impl Engine {
                 x.0.iter()
                     .try_fold(x.1.clone(), |mut map, (key, value_expr)| {
                         let value = self
-                            .eval_expr(scope, global, caches, lib, this_ptr, value_expr, level)?
+                            .eval_expr(global, caches, lib, level, scope, this_ptr, value_expr)?
                             .flatten();
 
                         #[cfg(not(feature = "unchecked"))]
@@ -465,7 +376,7 @@ impl Engine {
 
             Expr::And(x, ..) => {
                 let lhs = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, &x.lhs, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, &x.lhs)
                     .and_then(|v| {
                         v.as_bool().map_err(|typ| {
                             self.make_type_mismatch_err::<bool>(typ, x.lhs.position())
@@ -474,7 +385,7 @@ impl Engine {
 
                 match lhs {
                     Ok(true) => self
-                        .eval_expr(scope, global, caches, lib, this_ptr, &x.rhs, level)
+                        .eval_expr(global, caches, lib, level, scope, this_ptr, &x.rhs)
                         .and_then(|v| {
                             v.as_bool()
                                 .map_err(|typ| {
@@ -488,7 +399,7 @@ impl Engine {
 
             Expr::Or(x, ..) => {
                 let lhs = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, &x.lhs, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, &x.lhs)
                     .and_then(|v| {
                         v.as_bool().map_err(|typ| {
                             self.make_type_mismatch_err::<bool>(typ, x.lhs.position())
@@ -497,7 +408,7 @@ impl Engine {
 
                 match lhs {
                     Ok(false) => self
-                        .eval_expr(scope, global, caches, lib, this_ptr, &x.rhs, level)
+                        .eval_expr(global, caches, lib, level, scope, this_ptr, &x.rhs)
                         .and_then(|v| {
                             v.as_bool()
                                 .map_err(|typ| {
@@ -510,11 +421,11 @@ impl Engine {
             }
 
             Expr::Coalesce(x, ..) => {
-                let lhs = self.eval_expr(scope, global, caches, lib, this_ptr, &x.lhs, level);
+                let lhs = self.eval_expr(global, caches, lib, level, scope, this_ptr, &x.lhs);
 
                 match lhs {
                     Ok(value) if value.is::<()>() => {
-                        self.eval_expr(scope, global, caches, lib, this_ptr, &x.rhs, level)
+                        self.eval_expr(global, caches, lib, level, scope, this_ptr, &x.rhs)
                     }
                     _ => lhs,
                 }
@@ -535,7 +446,7 @@ impl Engine {
                     ))
                 })?;
                 let mut context =
-                    EvalContext::new(self, scope, global, Some(caches), lib, this_ptr, level);
+                    EvalContext::new(self, global, Some(caches), lib, level, scope, this_ptr);
 
                 let result = (custom_def.func)(&mut context, &expressions, &custom.state);
 
@@ -544,16 +455,16 @@ impl Engine {
 
             Expr::Stmt(x) if x.is_empty() => Ok(Dynamic::UNIT),
             Expr::Stmt(x) => {
-                self.eval_stmt_block(scope, global, caches, lib, this_ptr, x, true, level)
+                self.eval_stmt_block(global, caches, lib, level, scope, this_ptr, x, true)
             }
 
             #[cfg(not(feature = "no_index"))]
             Expr::Index(..) => self
-                .eval_dot_index_chain(scope, global, caches, lib, this_ptr, expr, level, &mut None),
+                .eval_dot_index_chain(global, caches, lib, level, scope, this_ptr, expr, &mut None),
 
             #[cfg(not(feature = "no_object"))]
             Expr::Dot(..) => self
-                .eval_dot_index_chain(scope, global, caches, lib, this_ptr, expr, level, &mut None),
+                .eval_dot_index_chain(global, caches, lib, level, scope, this_ptr, expr, &mut None),
 
             _ => unreachable!("expression cannot be evaluated: {:?}", expr),
         };
diff --git a/src/eval/global_state.rs b/src/eval/global_state.rs
index bf4489f9..db4c5332 100644
--- a/src/eval/global_state.rs
+++ b/src/eval/global_state.rs
@@ -286,6 +286,7 @@ impl GlobalRuntimeState<'_> {
     /// Get the current source.
     #[inline(always)]
     #[must_use]
+    #[allow(dead_code)]
     pub(crate) const fn source_raw(&self) -> Option<&ImmutableString> {
         self.source.as_ref()
     }
diff --git a/src/eval/stmt.rs b/src/eval/stmt.rs
index 0a302ee6..5bf03093 100644
--- a/src/eval/stmt.rs
+++ b/src/eval/stmt.rs
@@ -25,14 +25,14 @@ impl Engine {
     // Errors that are not recoverable, such as system errors or safety errors, can use `?`.
     pub(crate) fn eval_stmt_block(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         statements: &[Stmt],
         restore_orig_state: bool,
-        level: usize,
     ) -> RhaiResult {
         if statements.is_empty() {
             return Ok(Dynamic::UNIT);
@@ -53,14 +53,14 @@ impl Engine {
             let imports_len = global.num_imports();
 
             let result = self.eval_stmt(
-                scope,
                 global,
                 caches,
                 lib,
+                level,
+                scope,
                 this_ptr,
                 stmt,
                 restore_orig_state,
-                level,
             )?;
 
             #[cfg(not(feature = "no_module"))]
@@ -113,11 +113,11 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         op_info: &OpAssignment,
         target: &mut Target,
         root: (&str, Position),
         new_val: Dynamic,
-        level: usize,
     ) -> RhaiResultOf<()> {
         if target.is_read_only() {
             // Assignment to constant variable
@@ -130,8 +130,8 @@ impl Engine {
             let OpAssignment {
                 hash_op_assign,
                 hash_op,
-                op_assign,
-                op,
+                op_assign: op_assign_token,
+                op: op_token,
                 pos: op_pos,
             } = op_info;
 
@@ -142,27 +142,31 @@ impl Engine {
             let level = level + 1;
 
             if self.fast_operators() {
-                if let Some(func) = get_builtin_op_assignment_fn(op_assign, args[0], args[1]) {
+                if let Some(func) = get_builtin_op_assignment_fn(op_assign_token, args[0], args[1])
+                {
                     // Built-in found
-                    let op = op_assign.literal_syntax();
+                    let op = op_assign_token.literal_syntax();
                     let context = (self, op, None, &*global, lib, *op_pos, level).into();
                     return func(context, args).map(|_| ());
                 }
             }
 
-            let op_assign = op_assign.literal_syntax();
-            let op = op.literal_syntax();
+            let op_assign = op_assign_token.literal_syntax();
+            let op = op_token.literal_syntax();
+            let token = Some(op_assign_token);
 
-            match self.call_native_fn(
-                global, caches, lib, op_assign, hash, args, true, true, *op_pos, level,
+            match self.exec_native_fn_call(
+                global, caches, lib, level, op_assign, token, hash, args, true, *op_pos,
             ) {
                 Ok(_) => (),
                 Err(err) if matches!(*err, ERR::ErrorFunctionNotFound(ref f, ..) if f.starts_with(op_assign)) =>
                 {
                     // Expand to `var = var op rhs`
+                    let token = Some(op_token);
+
                     *args[0] = self
-                        .call_native_fn(
-                            global, caches, lib, op, *hash_op, args, true, false, *op_pos, level,
+                        .exec_native_fn_call(
+                            global, caches, lib, level, op, token, *hash_op, args, true, *op_pos,
                         )
                         .map_err(|err| err.fill_position(op_info.pos))?
                         .0
@@ -190,28 +194,28 @@ impl Engine {
     // Errors that are not recoverable, such as system errors or safety errors, can use `?`.
     pub(crate) fn eval_stmt(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         stmt: &Stmt,
         rewind_scope: bool,
-        level: usize,
     ) -> RhaiResult {
         #[cfg(feature = "debugging")]
         let reset_debugger =
-            self.run_debugger_with_reset(scope, global, lib, this_ptr, stmt, level)?;
+            self.run_debugger_with_reset(global, caches, lib, level, scope, this_ptr, stmt)?;
 
         // Coded this way for better branch prediction.
         // Popular branches are lifted out of the `match` statement into their own branches.
 
         // Function calls should account for a relatively larger portion of statements.
-        if let Stmt::FnCall(x, ..) = stmt {
+        if let Stmt::FnCall(x, pos) = stmt {
             self.track_operation(global, stmt.position())?;
 
             let result =
-                self.eval_fn_call_expr(scope, global, caches, lib, this_ptr, x, x.pos, level);
+                self.eval_fn_call_expr(global, caches, lib, level, scope, this_ptr, x, *pos);
 
             #[cfg(feature = "debugging")]
             global.debugger.reset_status(reset_debugger);
@@ -229,12 +233,12 @@ impl Engine {
 
             let result = if let Expr::Variable(x, ..) = lhs {
                 let rhs_result = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, rhs, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, rhs)
                     .map(Dynamic::flatten);
 
                 if let Ok(rhs_val) = rhs_result {
                     let search_result =
-                        self.search_namespace(scope, global, lib, this_ptr, lhs, level);
+                        self.search_namespace(global, caches, lib, level, scope, this_ptr, lhs);
 
                     if let Ok(search_val) = search_result {
                         let (mut lhs_ptr, pos) = search_val;
@@ -261,7 +265,7 @@ impl Engine {
                         let lhs_ptr = &mut lhs_ptr;
 
                         self.eval_op_assignment(
-                            global, caches, lib, op_info, lhs_ptr, root, rhs_val, level,
+                            global, caches, lib, level, op_info, lhs_ptr, root, rhs_val,
                         )
                         .map(|_| Dynamic::UNIT)
                     } else {
@@ -273,7 +277,7 @@ impl Engine {
             } else {
                 let (op_info, BinaryExpr { lhs, rhs }) = &**x;
 
-                let rhs_result = self.eval_expr(scope, global, caches, lib, this_ptr, rhs, level);
+                let rhs_result = self.eval_expr(global, caches, lib, level, scope, this_ptr, rhs);
 
                 if let Ok(rhs_val) = rhs_result {
                     // Check if the result is a string. If so, intern it.
@@ -303,14 +307,14 @@ impl Engine {
                         #[cfg(not(feature = "no_index"))]
                         Expr::Index(..) => self
                             .eval_dot_index_chain(
-                                scope, global, caches, lib, this_ptr, lhs, level, _new_val,
+                                global, caches, lib, level, scope, this_ptr, lhs, _new_val,
                             )
                             .map(|_| Dynamic::UNIT),
                         // dot_lhs.dot_rhs op= rhs
                         #[cfg(not(feature = "no_object"))]
                         Expr::Dot(..) => self
                             .eval_dot_index_chain(
-                                scope, global, caches, lib, this_ptr, lhs, level, _new_val,
+                                global, caches, lib, level, scope, this_ptr, lhs, _new_val,
                             )
                             .map(|_| Dynamic::UNIT),
                         _ => unreachable!("cannot assign to expression: {:?}", lhs),
@@ -334,13 +338,13 @@ impl Engine {
 
             // Expression as statement
             Stmt::Expr(expr) => self
-                .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                 .map(Dynamic::flatten),
 
             // Block scope
             Stmt::Block(statements, ..) if statements.is_empty() => Ok(Dynamic::UNIT),
             Stmt::Block(statements, ..) => self.eval_stmt_block(
-                scope, global, caches, lib, this_ptr, statements, true, level,
+                global, caches, lib, level, scope, this_ptr, statements, true,
             ),
 
             // If statement
@@ -348,7 +352,7 @@ impl Engine {
                 let (expr, if_block, else_block) = &**x;
 
                 let guard_val = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                     .and_then(|v| {
                         v.as_bool().map_err(|typ| {
                             self.make_type_mismatch_err::<bool>(typ, expr.position())
@@ -358,11 +362,11 @@ impl Engine {
                 match guard_val {
                     Ok(true) if if_block.is_empty() => Ok(Dynamic::UNIT),
                     Ok(true) => self.eval_stmt_block(
-                        scope, global, caches, lib, this_ptr, if_block, true, level,
+                        global, caches, lib, level, scope, this_ptr, if_block, true,
                     ),
                     Ok(false) if else_block.is_empty() => Ok(Dynamic::UNIT),
                     Ok(false) => self.eval_stmt_block(
-                        scope, global, caches, lib, this_ptr, else_block, true, level,
+                        global, caches, lib, level, scope, this_ptr, else_block, true,
                     ),
                     err => err.map(Into::into),
                 }
@@ -381,7 +385,7 @@ impl Engine {
                 ) = &**x;
 
                 let value_result =
-                    self.eval_expr(scope, global, caches, lib, this_ptr, expr, level);
+                    self.eval_expr(global, caches, lib, level, scope, this_ptr, expr);
 
                 if let Ok(value) = value_result {
                     let expr_result = if value.is_hashable() {
@@ -401,7 +405,7 @@ impl Engine {
                                 let cond_result = match block.condition {
                                     Expr::BoolConstant(b, ..) => Ok(b),
                                     ref c => self
-                                        .eval_expr(scope, global, caches, lib, this_ptr, c, level)
+                                        .eval_expr(global, caches, lib, level, scope, this_ptr, c)
                                         .and_then(|v| {
                                             v.as_bool().map_err(|typ| {
                                                 self.make_type_mismatch_err::<bool>(
@@ -432,7 +436,7 @@ impl Engine {
                                 let cond_result = match block.condition {
                                     Expr::BoolConstant(b, ..) => Ok(b),
                                     ref c => self
-                                        .eval_expr(scope, global, caches, lib, this_ptr, c, level)
+                                        .eval_expr(global, caches, lib, level, scope, this_ptr, c)
                                         .and_then(|v| {
                                             v.as_bool().map_err(|typ| {
                                                 self.make_type_mismatch_err::<bool>(
@@ -462,12 +466,12 @@ impl Engine {
                     };
 
                     if let Ok(Some(expr)) = expr_result {
-                        self.eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                        self.eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                     } else if let Ok(None) = expr_result {
                         // Default match clause
                         def_case.as_ref().map_or(Ok(Dynamic::UNIT), |&index| {
                             let def_expr = &expressions[index].expr;
-                            self.eval_expr(scope, global, caches, lib, this_ptr, def_expr, level)
+                            self.eval_expr(global, caches, lib, level, scope, this_ptr, def_expr)
                         })
                     } else {
                         expr_result.map(|_| Dynamic::UNIT)
@@ -488,7 +492,7 @@ impl Engine {
                 } else {
                     loop {
                         match self.eval_stmt_block(
-                            scope, global, caches, lib, this_ptr, body, true, level,
+                            global, caches, lib, level, scope, this_ptr, body, true,
                         ) {
                             Ok(_) => (),
                             Err(err) => match *err {
@@ -507,7 +511,7 @@ impl Engine {
 
                 loop {
                     let condition = self
-                        .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                        .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                         .and_then(|v| {
                             v.as_bool().map_err(|typ| {
                                 self.make_type_mismatch_err::<bool>(typ, expr.position())
@@ -519,7 +523,7 @@ impl Engine {
                         Ok(true) if body.is_empty() => (),
                         Ok(true) => {
                             match self.eval_stmt_block(
-                                scope, global, caches, lib, this_ptr, body, true, level,
+                                global, caches, lib, level, scope, this_ptr, body, true,
                             ) {
                                 Ok(_) => (),
                                 Err(err) => match *err {
@@ -542,7 +546,7 @@ impl Engine {
                 loop {
                     if !body.is_empty() {
                         match self.eval_stmt_block(
-                            scope, global, caches, lib, this_ptr, body, true, level,
+                            global, caches, lib, level, scope, this_ptr, body, true,
                         ) {
                             Ok(_) => (),
                             Err(err) => match *err {
@@ -554,7 +558,7 @@ impl Engine {
                     }
 
                     let condition = self
-                        .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                        .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                         .and_then(|v| {
                             v.as_bool().map_err(|typ| {
                                 self.make_type_mismatch_err::<bool>(typ, expr.position())
@@ -574,7 +578,7 @@ impl Engine {
                 let (var_name, counter, expr, statements) = &**x;
 
                 let iter_result = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                     .map(Dynamic::flatten);
 
                 if let Ok(iter_obj) = iter_result {
@@ -648,7 +652,7 @@ impl Engine {
                                 }
 
                                 self.eval_stmt_block(
-                                    scope, global, caches, lib, this_ptr, statements, true, level,
+                                    global, caches, lib, level, scope, this_ptr, statements, true,
                                 )
                                 .map(|_| Dynamic::UNIT)
                                 .or_else(|err| match *err {
@@ -677,7 +681,7 @@ impl Engine {
                 let is_break = options.contains(ASTFlags::BREAK);
 
                 if let Some(ref expr) = expr {
-                    self.eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                    self.eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                         .and_then(|v| ERR::LoopBreak(is_break, v, *pos).into())
                 } else {
                     Err(ERR::LoopBreak(is_break, Dynamic::UNIT, *pos).into())
@@ -696,7 +700,7 @@ impl Engine {
                 } = &**x;
 
                 let result = self
-                    .eval_stmt_block(scope, global, caches, lib, this_ptr, try_block, true, level)
+                    .eval_stmt_block(global, caches, lib, level, scope, this_ptr, try_block, true)
                     .map(|_| Dynamic::UNIT);
 
                 match result {
@@ -746,14 +750,14 @@ impl Engine {
                         }
 
                         let result = self.eval_stmt_block(
-                            scope,
                             global,
                             caches,
                             lib,
+                            level,
+                            scope,
                             this_ptr,
                             catch_block,
                             true,
-                            level,
                         );
 
                         scope.rewind(orig_scope_len);
@@ -775,7 +779,7 @@ impl Engine {
 
             // Throw value
             Stmt::Return(Some(expr), options, pos) if options.contains(ASTFlags::BREAK) => self
-                .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                 .and_then(|v| Err(ERR::ErrorRuntime(v.flatten(), *pos).into())),
 
             // Empty throw
@@ -785,7 +789,7 @@ impl Engine {
 
             // Return value
             Stmt::Return(Some(expr), .., pos) => self
-                .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                 .and_then(|v| Err(ERR::Return(v.flatten(), *pos).into())),
 
             // Empty return
@@ -817,7 +821,7 @@ impl Engine {
                         nesting_level,
                         will_shadow,
                     };
-                    let context = EvalContext::new(self, scope, global, None, lib, this_ptr, level);
+                    let context = EvalContext::new(self, global, None, lib, level, scope, this_ptr);
 
                     match filter(true, info, context) {
                         Ok(true) => None,
@@ -837,7 +841,7 @@ impl Engine {
                 } else {
                     // Evaluate initial value
                     let value_result = self
-                        .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                        .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                         .map(Dynamic::flatten);
 
                     if let Ok(mut value) = value_result {
@@ -900,7 +904,7 @@ impl Engine {
                 }
 
                 let path_result = self
-                    .eval_expr(scope, global, caches, lib, this_ptr, expr, level)
+                    .eval_expr(global, caches, lib, level, scope, this_ptr, expr)
                     .and_then(|v| {
                         let typ = v.type_name();
                         v.try_cast::<crate::ImmutableString>().ok_or_else(|| {
@@ -1006,4 +1010,28 @@ impl Engine {
 
         result
     }
+
+    /// Evaluate a list of statements with no `this` pointer.
+    /// This is commonly used to evaluate a list of statements in an [`AST`][crate::AST] or a script function body.
+    #[inline]
+    pub(crate) fn eval_global_statements(
+        &self,
+        global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
+        lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
+        statements: &[Stmt],
+    ) -> RhaiResult {
+        self.eval_stmt_block(
+            global, caches, lib, level, scope, &mut None, statements, false,
+        )
+        .or_else(|err| match *err {
+            ERR::Return(out, ..) => Ok(out),
+            ERR::LoopBreak(..) => {
+                unreachable!("no outer loop scope to break out of")
+            }
+            _ => Err(err),
+        })
+    }
 }
diff --git a/src/func/call.rs b/src/func/call.rs
index ef5d77e7..817a8d7b 100644
--- a/src/func/call.rs
+++ b/src/func/call.rs
@@ -1,19 +1,17 @@
 //! Implement function-calling mechanism for [`Engine`].
 
-use super::callable_function::CallableFunction;
-use super::{get_builtin_binary_op_fn, get_builtin_op_assignment_fn};
+use super::{get_builtin_binary_op_fn, get_builtin_op_assignment_fn, CallableFunction};
 use crate::api::default_limits::MAX_DYNAMIC_PARAMETERS;
-use crate::ast::{Expr, FnCallHashes, Stmt};
+use crate::ast::{Expr, FnCallExpr, FnCallHashes};
 use crate::engine::{
     KEYWORD_DEBUG, KEYWORD_EVAL, KEYWORD_FN_PTR, KEYWORD_FN_PTR_CALL, KEYWORD_FN_PTR_CURRY,
     KEYWORD_IS_DEF_VAR, KEYWORD_PRINT, KEYWORD_TYPE_OF,
 };
 use crate::eval::{Caches, FnResolutionCacheEntry, GlobalRuntimeState};
-use crate::tokenizer::Token;
+use crate::tokenizer::{is_valid_function_name, Token};
 use crate::{
-    calc_fn_hash, calc_fn_params_hash, combine_hashes, Dynamic, Engine, FnArgsVec, FnPtr,
-    ImmutableString, Module, OptimizationLevel, Position, RhaiError, RhaiResult, RhaiResultOf,
-    Scope, ERR,
+    calc_fn_hash, calc_fn_hash_full, Dynamic, Engine, FnArgsVec, FnPtr, ImmutableString, Module,
+    OptimizationLevel, Position, RhaiError, RhaiResult, RhaiResultOf, Scope, ERR,
 };
 #[cfg(feature = "no_std")]
 use hashbrown::hash_map::Entry;
@@ -108,17 +106,14 @@ impl Drop for ArgBackup<'_> {
     }
 }
 
+// Ensure no data races in function call arguments.
 #[cfg(not(feature = "no_closure"))]
 #[inline]
-pub fn ensure_no_data_race(
-    fn_name: &str,
-    args: &FnCallArgs,
-    is_method_call: bool,
-) -> RhaiResultOf<()> {
+pub fn ensure_no_data_race(fn_name: &str, args: &FnCallArgs, is_ref_mut: bool) -> RhaiResultOf<()> {
     if let Some((n, ..)) = args
         .iter()
         .enumerate()
-        .skip(if is_method_call { 1 } else { 0 })
+        .skip(if is_ref_mut { 1 } else { 0 })
         .find(|(.., a)| a.is_locked())
     {
         return Err(ERR::ErrorDataRace(
@@ -131,48 +126,32 @@ pub fn ensure_no_data_race(
     Ok(())
 }
 
-/// Generate the signature for a function call.
+/// Is a function name an anonymous function?
+#[cfg(not(feature = "no_function"))]
 #[inline]
 #[must_use]
-pub fn gen_fn_call_signature(engine: &Engine, fn_name: &str, args: &[&mut Dynamic]) -> String {
-    format!(
-        "{fn_name} ({})",
-        args.iter()
-            .map(|a| if a.is::<ImmutableString>() {
-                "&str | ImmutableString | String"
-            } else {
-                engine.map_type_name(a.type_name())
-            })
-            .collect::<FnArgsVec<_>>()
-            .join(", ")
-    )
-}
-
-/// Generate the signature for a namespace-qualified function call.
-///
-/// Not available under `no_module`.
-#[cfg(not(feature = "no_module"))]
-#[inline]
-#[must_use]
-pub fn gen_qualified_fn_call_signature(
-    engine: &Engine,
-    namespace: &crate::ast::Namespace,
-    fn_name: &str,
-    args: &[&mut Dynamic],
-) -> String {
-    let (ns, sep) = (
-        namespace.to_string(),
-        if namespace.is_empty() {
-            ""
-        } else {
-            crate::tokenizer::Token::DoubleColon.literal_syntax()
-        },
-    );
-
-    format!("{ns}{sep}{}", gen_fn_call_signature(engine, fn_name, args))
+pub fn is_anonymous_fn(name: &str) -> bool {
+    name.starts_with(crate::engine::FN_ANONYMOUS)
 }
 
 impl Engine {
+    /// Generate the signature for a function call.
+    #[inline]
+    #[must_use]
+    fn gen_fn_call_signature(&self, fn_name: &str, args: &[&mut Dynamic]) -> String {
+        format!(
+            "{fn_name} ({})",
+            args.iter()
+                .map(|a| if a.is::<ImmutableString>() {
+                    "&str | ImmutableString | String"
+                } else {
+                    self.map_type_name(a.type_name())
+                })
+                .collect::<FnArgsVec<_>>()
+                .join(", ")
+        )
+    }
+
     /// Resolve a normal (non-qualified) function call.
     ///
     /// Search order:
@@ -188,19 +167,17 @@ impl Engine {
         caches: &'s mut Caches,
         local_entry: &'s mut Option<FnResolutionCacheEntry>,
         lib: &[&Module],
-        fn_name: &str,
+        op_token: Option<&Token>,
         hash_base: u64,
         args: Option<&mut FnCallArgs>,
         allow_dynamic: bool,
-        op_assignment_token: Option<&Token>,
     ) -> Option<&'s FnResolutionCacheEntry> {
         if hash_base == 0 {
             return None;
         }
 
         let mut hash = args.as_ref().map_or(hash_base, |args| {
-            let hash_params = calc_fn_params_hash(args.iter().map(|a| a.type_id()));
-            combine_hashes(hash_base, hash_params)
+            calc_fn_hash_full(hash_base, args.iter().map(|a| a.type_id()))
         });
 
         let cache = caches.fn_resolution_cache_mut();
@@ -277,26 +254,25 @@ impl Engine {
                         }
 
                         // Try to find a built-in version
-                        let builtin = args.and_then(|args| {
-                            if let Some(op_assign) = op_assignment_token {
-                                let (first_arg, rest_args) = args.split_first().unwrap();
+                        let builtin =
+                            args.and_then(|args| match op_token {
+                                Some(token) if token.is_op_assignment() => {
+                                    let (first_arg, rest_args) = args.split_first().unwrap();
 
-                                get_builtin_op_assignment_fn(op_assign, *first_arg, rest_args[0])
+                                    get_builtin_op_assignment_fn(token, *first_arg, rest_args[0])
+                                        .map(|f| FnResolutionCacheEntry {
+                                            func: CallableFunction::from_fn_builtin(f),
+                                            source: None,
+                                        })
+                                }
+                                Some(token) => get_builtin_binary_op_fn(token, args[0], args[1])
                                     .map(|f| FnResolutionCacheEntry {
                                         func: CallableFunction::from_fn_builtin(f),
                                         source: None,
-                                    })
-                            } else if let Some(ref operator) = Token::lookup_from_syntax(fn_name) {
-                                get_builtin_binary_op_fn(operator, args[0], args[1]).map(|f| {
-                                    FnResolutionCacheEntry {
-                                        func: CallableFunction::from_fn_builtin(f),
-                                        source: None,
-                                    }
-                                })
-                            } else {
-                                None
-                            }
-                        });
+                                    }),
+
+                                None => None,
+                            });
 
                         return if cache.filter.is_absent_and_set(hash) {
                             // Do not cache "one-hit wonders"
@@ -309,7 +285,8 @@ impl Engine {
                     }
 
                     // Try all permutations with `Dynamic` wildcards
-                    let hash_params = calc_fn_params_hash(
+                    hash = calc_fn_hash_full(
+                        hash_base,
                         args.as_ref()
                             .expect("no permutations")
                             .iter()
@@ -324,7 +301,6 @@ impl Engine {
                                 }
                             }),
                     );
-                    hash = combine_hashes(hash_base, hash_params);
 
                     bitmask += 1;
                 }
@@ -343,27 +319,21 @@ impl Engine {
     ///
     /// **DO NOT** reuse the argument values unless for the first `&mut` argument -
     /// all others are silently replaced by `()`!
-    pub(crate) fn call_native_fn(
+    pub(crate) fn exec_native_fn_call(
         &self,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         name: &str,
+        op_token: Option<&Token>,
         hash: u64,
         args: &mut FnCallArgs,
         is_ref_mut: bool,
-        is_op_assign: bool,
         pos: Position,
-        level: usize,
     ) -> RhaiResultOf<(Dynamic, bool)> {
         self.track_operation(global, pos)?;
 
-        let op_assign = if is_op_assign {
-            Token::lookup_from_syntax(name)
-        } else {
-            None
-        };
-
         // Check if function access already in the cache
         let local_entry = &mut None;
 
@@ -372,11 +342,10 @@ impl Engine {
             caches,
             local_entry,
             lib,
-            name,
+            op_token,
             hash,
             Some(args),
             true,
-            op_assign.as_ref(),
         );
 
         if func.is_some() {
@@ -445,7 +414,9 @@ impl Engine {
                         Ok(ref r) => crate::eval::DebuggerEvent::FunctionExitWithValue(r),
                         Err(ref err) => crate::eval::DebuggerEvent::FunctionExitWithError(err),
                     };
-                    match self.run_debugger_raw(scope, global, lib, &mut None, node, event, level) {
+                    match self
+                        .run_debugger_raw(global, caches, lib, level, scope, &mut None, node, event)
+                    {
                         Ok(_) => (),
                         Err(err) => _result = Err(err),
                     }
@@ -547,7 +518,7 @@ impl Engine {
 
             // Raise error
             _ => {
-                Err(ERR::ErrorFunctionNotFound(gen_fn_call_signature(self, name, args), pos).into())
+                Err(ERR::ErrorFunctionNotFound(self.gen_fn_call_signature(name, args), pos).into())
             }
         }
     }
@@ -565,18 +536,18 @@ impl Engine {
     /// all others are silently replaced by `()`!
     pub(crate) fn exec_fn_call(
         &self,
-        _scope: Option<&mut Scope>,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        _scope: Option<&mut Scope>,
         fn_name: &str,
-        _native_only: bool,
+        op_token: Option<&Token>,
         hashes: FnCallHashes,
         args: &mut FnCallArgs,
         is_ref_mut: bool,
         _is_method_call: bool,
         pos: Position,
-        level: usize,
     ) -> RhaiResultOf<(Dynamic, bool)> {
         fn no_method_err(name: &str, pos: Position) -> RhaiResultOf<(Dynamic, bool)> {
             Err(ERR::ErrorRuntime(
@@ -590,55 +561,58 @@ impl Engine {
         #[cfg(not(feature = "no_closure"))]
         ensure_no_data_race(fn_name, args, is_ref_mut)?;
 
-        // These may be redirected from method style calls.
-        match fn_name {
-            // Handle type_of()
-            KEYWORD_TYPE_OF if args.len() == 1 => {
-                let typ = self.map_type_name(args[0].type_name()).to_string().into();
-                return Ok((typ, false));
-            }
-
-            // Handle is_def_fn()
-            #[cfg(not(feature = "no_function"))]
-            crate::engine::KEYWORD_IS_DEF_FN
-                if args.len() == 2 && args[0].is::<FnPtr>() && args[1].is::<crate::INT>() =>
-            {
-                let fn_name = args[0].read_lock::<ImmutableString>().expect("`FnPtr`");
-                let num_params = args[1].as_int().expect("`INT`");
-
-                return Ok((
-                    if num_params < 0 || num_params > crate::MAX_USIZE_INT {
-                        false
-                    } else {
-                        let hash_script = calc_fn_hash(None, fn_name.as_str(), num_params as usize);
-                        self.has_script_fn(Some(global), caches, lib, hash_script)
-                    }
-                    .into(),
-                    false,
-                ));
-            }
-
-            // Handle is_shared()
-            #[cfg(not(feature = "no_closure"))]
-            crate::engine::KEYWORD_IS_SHARED if args.len() == 1 => {
-                return no_method_err(fn_name, pos)
-            }
-
-            KEYWORD_FN_PTR | KEYWORD_EVAL | KEYWORD_IS_DEF_VAR if args.len() == 1 => {
-                return no_method_err(fn_name, pos)
-            }
-
-            KEYWORD_FN_PTR_CALL | KEYWORD_FN_PTR_CURRY if !args.is_empty() => {
-                return no_method_err(fn_name, pos)
-            }
-
-            _ => (),
-        }
-
         let level = level + 1;
 
+        // These may be redirected from method style calls.
+        if hashes.is_native_only() {
+            match fn_name {
+                // Handle type_of()
+                KEYWORD_TYPE_OF if args.len() == 1 => {
+                    let typ = self.map_type_name(args[0].type_name()).to_string().into();
+                    return Ok((typ, false));
+                }
+
+                // Handle is_def_fn()
+                #[cfg(not(feature = "no_function"))]
+                crate::engine::KEYWORD_IS_DEF_FN
+                    if args.len() == 2 && args[0].is::<FnPtr>() && args[1].is::<crate::INT>() =>
+                {
+                    let fn_name = args[0].read_lock::<ImmutableString>().expect("`FnPtr`");
+                    let num_params = args[1].as_int().expect("`INT`");
+
+                    return Ok((
+                        if num_params < 0 || num_params > crate::MAX_USIZE_INT {
+                            false
+                        } else {
+                            let hash_script =
+                                calc_fn_hash(None, fn_name.as_str(), num_params as usize);
+                            self.has_script_fn(Some(global), caches, lib, hash_script)
+                        }
+                        .into(),
+                        false,
+                    ));
+                }
+
+                // Handle is_shared()
+                #[cfg(not(feature = "no_closure"))]
+                crate::engine::KEYWORD_IS_SHARED if args.len() == 1 => {
+                    return no_method_err(fn_name, pos)
+                }
+
+                KEYWORD_FN_PTR | KEYWORD_EVAL | KEYWORD_IS_DEF_VAR if args.len() == 1 => {
+                    return no_method_err(fn_name, pos)
+                }
+
+                KEYWORD_FN_PTR_CALL | KEYWORD_FN_PTR_CURRY if !args.is_empty() => {
+                    return no_method_err(fn_name, pos)
+                }
+
+                _ => (),
+            }
+        }
+
         #[cfg(not(feature = "no_function"))]
-        if !_native_only {
+        if !hashes.is_native_only() {
             // Script-defined function call?
             let local_entry = &mut None;
 
@@ -648,11 +622,10 @@ impl Engine {
                     caches,
                     local_entry,
                     lib,
-                    fn_name,
-                    hashes.script,
+                    None,
+                    hashes.script(),
                     None,
                     false,
-                    None,
                 )
                 .cloned()
             {
@@ -681,16 +654,16 @@ impl Engine {
                     let (first_arg, rest_args) = args.split_first_mut().unwrap();
 
                     self.call_script_fn(
-                        scope,
                         global,
                         caches,
                         lib,
+                        level,
+                        scope,
                         &mut Some(*first_arg),
                         func,
                         rest_args,
                         true,
                         pos,
-                        level,
                     )
                 } else {
                     // Normal call of script function
@@ -702,7 +675,7 @@ impl Engine {
                     }
 
                     let result = self.call_script_fn(
-                        scope, global, caches, lib, &mut None, func, args, true, pos, level,
+                        global, caches, lib, level, scope, &mut None, func, args, true, pos,
                     );
 
                     // Restore the original reference
@@ -714,60 +687,38 @@ impl Engine {
                 // Restore the original source
                 global.source = orig_source;
 
-                return Ok((result?, false));
+                return result.map(|r| (r, false));
             }
         }
 
         // Native function call
-        let hash = hashes.native;
-        self.call_native_fn(
-            global, caches, lib, fn_name, hash, args, is_ref_mut, false, pos, level,
-        )
-    }
+        let hash = hashes.native();
 
-    /// Evaluate a list of statements with no `this` pointer.
-    /// This is commonly used to evaluate a list of statements in an [`AST`][crate::AST] or a script function body.
-    #[inline]
-    pub(crate) fn eval_global_statements(
-        &self,
-        scope: &mut Scope,
-        global: &mut GlobalRuntimeState,
-        caches: &mut Caches,
-        statements: &[Stmt],
-        lib: &[&Module],
-        level: usize,
-    ) -> RhaiResult {
-        self.eval_stmt_block(
-            scope, global, caches, lib, &mut None, statements, false, level,
+        self.exec_native_fn_call(
+            global, caches, lib, level, fn_name, op_token, hash, args, is_ref_mut, pos,
         )
-        .or_else(|err| match *err {
-            ERR::Return(out, ..) => Ok(out),
-            ERR::LoopBreak(..) => {
-                unreachable!("no outer loop scope to break out of")
-            }
-            _ => Err(err),
-        })
     }
 
     /// Evaluate an argument.
     #[inline]
     pub(crate) fn get_arg_value(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         arg_expr: &Expr,
-        level: usize,
     ) -> RhaiResultOf<(Dynamic, Position)> {
-        #[cfg(feature = "debugging")]
-        if self.debugger.is_some() {
-            if let Some(value) = arg_expr.get_literal_value() {
-                #[cfg(feature = "debugging")]
-                self.run_debugger(scope, global, lib, this_ptr, arg_expr, level)?;
-                return Ok((value, arg_expr.start_position()));
-            }
+        // Literal values
+        if let Some(value) = arg_expr.get_literal_value() {
+            self.track_operation(global, arg_expr.start_position())?;
+
+            #[cfg(feature = "debugging")]
+            self.run_debugger(global, caches, lib, level, scope, this_ptr, arg_expr)?;
+
+            return Ok((value, arg_expr.start_position()));
         }
 
         // Do not match function exit for arguments
@@ -776,13 +727,13 @@ impl Engine {
             matches!(status, crate::eval::DebuggerStatus::FunctionExit(..))
         });
 
-        let result = self.eval_expr(scope, global, caches, lib, this_ptr, arg_expr, level);
+        let result = self.eval_expr(global, caches, lib, level, scope, this_ptr, arg_expr);
 
         // Restore function exit status
         #[cfg(feature = "debugging")]
         global.debugger.reset_status(reset_debugger);
 
-        Ok((result?, arg_expr.start_position()))
+        result.map(|r| (r, arg_expr.start_position()))
     }
 
     /// Call a dot method.
@@ -792,13 +743,13 @@ impl Engine {
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
         fn_name: &str,
         mut hash: FnCallHashes,
         target: &mut crate::eval::Target,
         mut call_args: &mut [Dynamic],
         first_arg_pos: Position,
         fn_call_pos: Position,
-        level: usize,
     ) -> RhaiResultOf<(Dynamic, bool)> {
         let is_ref_mut = target.is_ref();
 
@@ -806,11 +757,21 @@ impl Engine {
             KEYWORD_FN_PTR_CALL if target.is::<FnPtr>() => {
                 // FnPtr call
                 let fn_ptr = target.read_lock::<FnPtr>().expect("`FnPtr`");
+
+                #[cfg(not(feature = "no_function"))]
+                let is_anon = fn_ptr.is_anonymous();
+                #[cfg(feature = "no_function")]
+                let is_anon = false;
+
                 // Redirect function name
                 let fn_name = fn_ptr.fn_name();
-                let args_len = call_args.len() + fn_ptr.curry().len();
                 // Recalculate hashes
-                let new_hash = calc_fn_hash(None, fn_name, args_len).into();
+                let args_len = call_args.len() + fn_ptr.curry().len();
+                let new_hash = if !is_anon && !is_valid_function_name(fn_name) {
+                    FnCallHashes::from_native(calc_fn_hash(None, fn_name, args_len))
+                } else {
+                    calc_fn_hash(None, fn_name, args_len).into()
+                };
                 // Arguments are passed as-is, adding the curried arguments
                 let mut curry = FnArgsVec::with_capacity(fn_ptr.curry().len());
                 curry.extend(fn_ptr.curry().iter().cloned());
@@ -820,18 +781,18 @@ impl Engine {
 
                 // Map it to name(args) in function-call style
                 self.exec_fn_call(
-                    None,
                     global,
                     caches,
                     lib,
+                    level,
+                    None,
                     fn_name,
-                    false,
+                    None,
                     new_hash,
                     &mut args,
                     false,
                     false,
                     fn_call_pos,
-                    level,
                 )
             }
             KEYWORD_FN_PTR_CALL => {
@@ -845,20 +806,30 @@ impl Engine {
 
                 // FnPtr call on object
                 let fn_ptr = mem::take(&mut call_args[0]).cast::<FnPtr>();
+
+                #[cfg(not(feature = "no_function"))]
+                let is_anon = fn_ptr.is_anonymous();
+                #[cfg(feature = "no_function")]
+                let is_anon = false;
+
                 call_args = &mut call_args[1..];
 
                 // Redirect function name
-                let fn_name = fn_ptr.fn_name();
-                let args_len = call_args.len() + fn_ptr.curry().len();
+                let (fn_name, fn_curry) = fn_ptr.take_data();
                 // Recalculate hash
-                let new_hash = FnCallHashes::from_all(
-                    #[cfg(not(feature = "no_function"))]
-                    calc_fn_hash(None, fn_name, args_len),
-                    calc_fn_hash(None, fn_name, args_len + 1),
-                );
+                let args_len = call_args.len() + fn_curry.len();
+                let new_hash = if !is_anon && !is_valid_function_name(&fn_name) {
+                    FnCallHashes::from_native(calc_fn_hash(None, &fn_name, args_len + 1))
+                } else {
+                    FnCallHashes::from_all(
+                        #[cfg(not(feature = "no_function"))]
+                        calc_fn_hash(None, &fn_name, args_len),
+                        calc_fn_hash(None, &fn_name, args_len + 1),
+                    )
+                };
                 // Replace the first argument with the object pointer, adding the curried arguments
-                let mut curry = FnArgsVec::with_capacity(fn_ptr.curry().len());
-                curry.extend(fn_ptr.curry().iter().cloned());
+                let mut curry = FnArgsVec::with_capacity(fn_curry.len());
+                curry.extend(fn_curry.into_iter());
                 let mut args = FnArgsVec::with_capacity(curry.len() + call_args.len() + 1);
                 args.push(target.as_mut());
                 args.extend(curry.iter_mut());
@@ -866,18 +837,18 @@ impl Engine {
 
                 // Map it to name(args) in function-call style
                 self.exec_fn_call(
-                    None,
                     global,
                     caches,
                     lib,
-                    fn_name,
-                    false,
+                    level,
+                    None,
+                    &fn_name,
+                    None,
                     new_hash,
                     &mut args,
                     is_ref_mut,
                     true,
                     fn_call_pos,
-                    level,
                 )
             }
             KEYWORD_FN_PTR_CURRY => {
@@ -925,6 +896,11 @@ impl Engine {
                 if let Some(map) = target.read_lock::<crate::Map>() {
                     if let Some(val) = map.get(fn_name) {
                         if let Some(fn_ptr) = val.read_lock::<FnPtr>() {
+                            #[cfg(not(feature = "no_function"))]
+                            let is_anon = fn_ptr.is_anonymous();
+                            #[cfg(feature = "no_function")]
+                            let is_anon = false;
+
                             // Remap the function name
                             _redirected = fn_ptr.fn_name_raw().clone();
                             fn_name = &_redirected;
@@ -939,11 +915,19 @@ impl Engine {
                                 call_args = &mut _arg_values;
                             }
                             // Recalculate the hash based on the new function name and new arguments
-                            hash = FnCallHashes::from_all(
-                                #[cfg(not(feature = "no_function"))]
-                                calc_fn_hash(None, fn_name, call_args.len()),
-                                calc_fn_hash(None, fn_name, call_args.len() + 1),
-                            );
+                            hash = if !is_anon && !is_valid_function_name(&fn_name) {
+                                FnCallHashes::from_native(calc_fn_hash(
+                                    None,
+                                    fn_name,
+                                    call_args.len() + 1,
+                                ))
+                            } else {
+                                FnCallHashes::from_all(
+                                    #[cfg(not(feature = "no_function"))]
+                                    calc_fn_hash(None, fn_name, call_args.len()),
+                                    calc_fn_hash(None, fn_name, call_args.len() + 1),
+                                )
+                            };
                         }
                     }
                 };
@@ -954,18 +938,18 @@ impl Engine {
                 args.extend(call_args.iter_mut());
 
                 self.exec_fn_call(
-                    None,
                     global,
                     caches,
                     lib,
+                    level,
+                    None,
                     fn_name,
-                    false,
+                    None,
                     hash,
                     &mut args,
                     is_ref_mut,
                     true,
                     fn_call_pos,
-                    level,
                 )
             }
         }?;
@@ -981,22 +965,20 @@ impl Engine {
     /// Call a function in normal function-call style.
     pub(crate) fn make_function_call(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         fn_name: &str,
-        native_only: bool,
+        op_token: Option<&Token>,
         first_arg: Option<&Expr>,
         args_expr: &[Expr],
         hashes: FnCallHashes,
         capture_scope: bool,
-        operator_token: Option<&Token>,
         pos: Position,
-        level: usize,
     ) -> RhaiResult {
-        let native = native_only;
         let mut first_arg = first_arg;
         let mut a_expr = args_expr;
         let mut total_args = if first_arg.is_some() { 1 } else { 0 } + a_expr.len();
@@ -1006,13 +988,13 @@ impl Engine {
         let redirected; // Handle call() - Redirect function call
 
         match name {
-            _ if operator_token.is_some() => (),
+            _ if op_token.is_some() => (),
 
             // Handle call()
             KEYWORD_FN_PTR_CALL if total_args >= 1 => {
                 let arg = first_arg.unwrap();
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, arg, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg)?;
 
                 if !arg_value.is::<FnPtr>() {
                     let typ = self.map_type_name(arg_value.type_name());
@@ -1020,10 +1002,17 @@ impl Engine {
                 }
 
                 let fn_ptr = arg_value.cast::<FnPtr>();
-                curry.extend(fn_ptr.curry().iter().cloned());
+
+                #[cfg(not(feature = "no_function"))]
+                let is_anon = fn_ptr.is_anonymous();
+                #[cfg(feature = "no_function")]
+                let is_anon = false;
+
+                let (fn_name, fn_curry) = fn_ptr.take_data();
+                curry.extend(fn_curry.into_iter());
 
                 // Redirect function name
-                redirected = fn_ptr.take_data().0;
+                redirected = fn_name;
                 name = &redirected;
 
                 // Shift the arguments
@@ -1035,7 +1024,8 @@ impl Engine {
 
                 // Recalculate hash
                 let args_len = total_args + curry.len();
-                hashes = if hashes.is_native_only() {
+
+                hashes = if !is_anon && !is_valid_function_name(name) {
                     FnCallHashes::from_native(calc_fn_hash(None, name, args_len))
                 } else {
                     calc_fn_hash(None, name, args_len).into()
@@ -1045,7 +1035,7 @@ impl Engine {
             KEYWORD_FN_PTR if total_args == 1 => {
                 let arg = first_arg.unwrap();
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, arg, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg)?;
 
                 // Fn - only in function call style
                 return arg_value
@@ -1060,7 +1050,7 @@ impl Engine {
             KEYWORD_FN_PTR_CURRY if total_args > 1 => {
                 let first = first_arg.unwrap();
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, first, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, first)?;
 
                 if !arg_value.is::<FnPtr>() {
                     let typ = self.map_type_name(arg_value.type_name());
@@ -1072,7 +1062,7 @@ impl Engine {
                 // Append the new curried arguments to the existing list.
                 let fn_curry = a_expr.iter().try_fold(fn_curry, |mut curried, expr| {
                     let (value, ..) =
-                        self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)?;
+                        self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)?;
                     curried.push(value);
                     Ok::<_, RhaiError>(curried)
                 })?;
@@ -1085,7 +1075,7 @@ impl Engine {
             crate::engine::KEYWORD_IS_SHARED if total_args == 1 => {
                 let arg = first_arg.unwrap();
                 let (arg_value, ..) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, arg, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg)?;
                 return Ok(arg_value.is_shared().into());
             }
 
@@ -1094,14 +1084,14 @@ impl Engine {
             crate::engine::KEYWORD_IS_DEF_FN if total_args == 2 => {
                 let first = first_arg.unwrap();
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, first, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, first)?;
 
                 let fn_name = arg_value
                     .into_immutable_string()
                     .map_err(|typ| self.make_type_mismatch_err::<ImmutableString>(typ, arg_pos))?;
 
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, &a_expr[0], level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, &a_expr[0])?;
 
                 let num_params = arg_value
                     .as_int()
@@ -1120,7 +1110,7 @@ impl Engine {
             KEYWORD_IS_DEF_VAR if total_args == 1 => {
                 let arg = first_arg.unwrap();
                 let (arg_value, arg_pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, arg, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg)?;
                 let var_name = arg_value
                     .into_immutable_string()
                     .map_err(|typ| self.make_type_mismatch_err::<ImmutableString>(typ, arg_pos))?;
@@ -1135,12 +1125,12 @@ impl Engine {
                 let orig_imports_len = global.num_imports();
                 let arg = first_arg.unwrap();
                 let (arg_value, pos) =
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, arg, level)?;
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, arg)?;
                 let s = &arg_value
                     .into_immutable_string()
                     .map_err(|typ| self.make_type_mismatch_err::<ImmutableString>(typ, pos))?;
                 let result =
-                    self.eval_script_expr_in_place(scope, global, caches, lib, s, pos, level + 1);
+                    self.eval_script_expr_in_place(global, caches, lib, level + 1, scope, s, pos);
 
                 // IMPORTANT! If the eval defines new variables in the current scope,
                 //            all variable offsets from this point on will be mis-aligned.
@@ -1182,7 +1172,7 @@ impl Engine {
                 .copied()
                 .chain(a_expr.iter())
                 .try_for_each(|expr| {
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)
                         .map(|(value, ..)| arg_values.push(value.flatten()))
                 })?;
             args.extend(curry.iter_mut());
@@ -1193,8 +1183,8 @@ impl Engine {
 
             return self
                 .exec_fn_call(
-                    scope, global, caches, lib, name, native, hashes, &mut args, is_ref_mut, false,
-                    pos, level,
+                    global, caches, lib, level, scope, name, op_token, hashes, &mut args,
+                    is_ref_mut, false, pos,
                 )
                 .map(|(v, ..)| v);
         }
@@ -1210,16 +1200,16 @@ impl Engine {
                 let first_expr = first_arg.unwrap();
 
                 #[cfg(feature = "debugging")]
-                self.run_debugger(scope, global, lib, this_ptr, first_expr, level)?;
+                self.run_debugger(global, caches, lib, level, scope, this_ptr, first_expr)?;
 
                 // func(x, ...) -> x.func(...)
                 a_expr.iter().try_for_each(|expr| {
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)
                         .map(|(value, ..)| arg_values.push(value.flatten()))
                 })?;
 
                 let (mut target, _pos) =
-                    self.search_namespace(scope, global, lib, this_ptr, first_expr, level)?;
+                    self.search_namespace(global, caches, lib, level, scope, this_ptr, first_expr)?;
 
                 if target.is_read_only() {
                     target = target.into_owned();
@@ -1246,7 +1236,7 @@ impl Engine {
                     .into_iter()
                     .chain(a_expr.iter())
                     .try_for_each(|expr| {
-                        self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)
+                        self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)
                             .map(|(value, ..)| arg_values.push(value.flatten()))
                     })?;
                 args.extend(curry.iter_mut());
@@ -1256,8 +1246,8 @@ impl Engine {
         }
 
         self.exec_fn_call(
-            None, global, caches, lib, name, native, hashes, &mut args, is_ref_mut, false, pos,
-            level,
+            global, caches, lib, level, None, name, op_token, hashes, &mut args, is_ref_mut, false,
+            pos,
         )
         .map(|(v, ..)| v)
     }
@@ -1266,17 +1256,17 @@ impl Engine {
     #[cfg(not(feature = "no_module"))]
     pub(crate) fn make_qualified_function_call(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         namespace: &crate::ast::Namespace,
         fn_name: &str,
         args_expr: &[Expr],
         hash: u64,
         pos: Position,
-        level: usize,
     ) -> RhaiResult {
         let mut arg_values = FnArgsVec::with_capacity(args_expr.len());
         let mut args = FnArgsVec::with_capacity(args_expr.len());
@@ -1290,20 +1280,20 @@ impl Engine {
             // and avoid cloning the value
             if !args_expr.is_empty() && args_expr[0].is_variable_access(true) {
                 #[cfg(feature = "debugging")]
-                self.run_debugger(scope, global, lib, this_ptr, &args_expr[0], level)?;
+                self.run_debugger(global, caches, lib, level, scope, this_ptr, &args_expr[0])?;
 
                 // func(x, ...) -> x.func(...)
                 arg_values.push(Dynamic::UNIT);
 
                 args_expr.iter().skip(1).try_for_each(|expr| {
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)
                         .map(|(value, ..)| arg_values.push(value.flatten()))
                 })?;
 
                 // Get target reference to first argument
                 let first_arg = &args_expr[0];
                 let (target, _pos) =
-                    self.search_scope_only(scope, global, lib, this_ptr, first_arg, level)?;
+                    self.search_scope_only(global, caches, lib, level, scope, this_ptr, first_arg)?;
 
                 self.track_operation(global, _pos)?;
 
@@ -1326,7 +1316,7 @@ impl Engine {
             } else {
                 // func(..., ...) or func(mod::x, ...)
                 args_expr.iter().try_for_each(|expr| {
-                    self.get_arg_value(scope, global, caches, lib, this_ptr, expr, level)
+                    self.get_arg_value(global, caches, lib, level, scope, this_ptr, expr)
                         .map(|(value, ..)| arg_values.push(value.flatten()))
                 })?;
                 args.extend(arg_values.iter_mut());
@@ -1343,9 +1333,7 @@ impl Engine {
             // Then search native Rust functions
             None => {
                 self.track_operation(global, pos)?;
-                let hash_params = calc_fn_params_hash(args.iter().map(|a| a.type_id()));
-                let hash_qualified_fn = combine_hashes(hash, hash_params);
-
+                let hash_qualified_fn = calc_fn_hash_full(hash, args.iter().map(|a| a.type_id()));
                 module.get_qualified_fn(hash_qualified_fn)
             }
             r => r,
@@ -1363,16 +1351,18 @@ impl Engine {
 
             // Try all permutations with `Dynamic` wildcards
             while bitmask < max_bitmask {
-                let hash_params = calc_fn_params_hash(args.iter().enumerate().map(|(i, a)| {
-                    let mask = 1usize << (num_args - i - 1);
-                    if bitmask & mask == 0 {
-                        a.type_id()
-                    } else {
-                        // Replace with `Dynamic`
-                        TypeId::of::<Dynamic>()
-                    }
-                }));
-                let hash_qualified_fn = combine_hashes(hash, hash_params);
+                let hash_qualified_fn = calc_fn_hash_full(
+                    hash,
+                    args.iter().enumerate().map(|(i, a)| {
+                        let mask = 1usize << (num_args - i - 1);
+                        if bitmask & mask == 0 {
+                            a.type_id()
+                        } else {
+                            // Replace with `Dynamic`
+                            TypeId::of::<Dynamic>()
+                        }
+                    }),
+                );
 
                 self.track_operation(global, pos)?;
 
@@ -1403,7 +1393,7 @@ impl Engine {
                 let orig_source = mem::replace(&mut global.source, module.id_raw().cloned());
 
                 let result = self.call_script_fn(
-                    new_scope, global, caches, lib, &mut None, fn_def, &mut args, true, pos, level,
+                    global, caches, lib, level, new_scope, &mut None, fn_def, &mut args, true, pos,
                 );
 
                 global.source = orig_source;
@@ -1431,24 +1421,32 @@ impl Engine {
 
             Some(f) => unreachable!("unknown function type: {:?}", f),
 
-            None => Err(ERR::ErrorFunctionNotFound(
-                gen_qualified_fn_call_signature(self, namespace, fn_name, &args),
-                pos,
-            )
-            .into()),
+            None => {
+                let sig = if namespace.is_empty() {
+                    self.gen_fn_call_signature(fn_name, &args)
+                } else {
+                    format!(
+                        "{namespace}{}{}",
+                        crate::tokenizer::Token::DoubleColon.literal_syntax(),
+                        self.gen_fn_call_signature(fn_name, &args)
+                    )
+                };
+
+                Err(ERR::ErrorFunctionNotFound(sig, pos).into())
+            }
         }
     }
 
     /// Evaluate a text script in place - used primarily for 'eval'.
     pub(crate) fn eval_script_expr_in_place(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         script: &str,
         _pos: Position,
-        level: usize,
     ) -> RhaiResult {
         self.track_operation(global, _pos)?;
 
@@ -1481,6 +1479,83 @@ impl Engine {
         }
 
         // Evaluate the AST
-        self.eval_global_statements(scope, global, caches, statements, lib, level)
+        self.eval_global_statements(global, caches, lib, level, scope, statements)
+    }
+
+    /// Evaluate a function call expression.
+    pub(crate) fn eval_fn_call_expr(
+        &self,
+        global: &mut GlobalRuntimeState,
+        caches: &mut Caches,
+        lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
+        this_ptr: &mut Option<&mut Dynamic>,
+        expr: &FnCallExpr,
+        pos: Position,
+    ) -> RhaiResult {
+        let FnCallExpr {
+            #[cfg(not(feature = "no_module"))]
+            namespace,
+            name,
+            hashes,
+            args,
+            op_token,
+            capture_parent_scope: capture,
+            ..
+        } = expr;
+
+        let op_token = op_token.as_ref();
+
+        // Short-circuit native binary operator call if under Fast Operators mode
+        if op_token.is_some() && self.fast_operators() && args.len() == 2 {
+            let mut lhs = self
+                .get_arg_value(global, caches, lib, level, scope, this_ptr, &args[0])?
+                .0
+                .flatten();
+
+            let mut rhs = self
+                .get_arg_value(global, caches, lib, level, scope, this_ptr, &args[1])?
+                .0
+                .flatten();
+
+            let operands = &mut [&mut lhs, &mut rhs];
+
+            if let Some(func) =
+                get_builtin_binary_op_fn(op_token.as_ref().unwrap(), operands[0], operands[1])
+            {
+                // Built-in found
+                let context = (self, name.as_str(), None, &*global, lib, pos, level + 1).into();
+                return func(context, operands);
+            }
+
+            return self
+                .exec_fn_call(
+                    global, caches, lib, level, None, name, op_token, *hashes, operands, false,
+                    false, pos,
+                )
+                .map(|(v, ..)| v);
+        }
+
+        #[cfg(not(feature = "no_module"))]
+        if !namespace.is_empty() {
+            // Qualified function call
+            let hash = hashes.native();
+
+            return self.make_qualified_function_call(
+                global, caches, lib, level, scope, this_ptr, namespace, name, args, hash, pos,
+            );
+        }
+
+        // Normal function call
+        let (first_arg, args) = args.split_first().map_or_else(
+            || (None, args.as_ref()),
+            |(first, rest)| (Some(first), rest),
+        );
+
+        self.make_function_call(
+            global, caches, lib, level, scope, this_ptr, name, op_token, first_arg, args, *hashes,
+            *capture, pos,
+        )
     }
 }
diff --git a/src/func/hashing.rs b/src/func/hashing.rs
index 855dcd3d..2b457c4d 100644
--- a/src/func/hashing.rs
+++ b/src/func/hashing.rs
@@ -156,7 +156,7 @@ pub fn calc_fn_hash<'a>(
     }
 }
 
-/// Calculate a non-zero [`u64`] hash key from a list of parameter types.
+/// Calculate a non-zero [`u64`] hash key from a base [`u64`] hash key and a list of parameter types.
 ///
 /// Parameter types are passed in via [`TypeId`] values from an iterator.
 ///
@@ -165,10 +165,12 @@ pub fn calc_fn_hash<'a>(
 /// If the hash happens to be zero, it is mapped to `DEFAULT_HASH`.
 #[inline]
 #[must_use]
-pub fn calc_fn_params_hash(
+pub fn calc_fn_hash_full(
+    base: u64,
     params: impl IntoIterator<Item = TypeId, IntoIter = impl ExactSizeIterator<Item = TypeId>>,
 ) -> u64 {
     let s = &mut get_hasher();
+    base.hash(s);
     let iter = params.into_iter();
     let len = iter.len();
     iter.for_each(|t| {
@@ -181,17 +183,3 @@ pub fn calc_fn_params_hash(
         r => r,
     }
 }
-
-/// Combine two [`u64`] hashes by taking the XOR of them.
-///
-/// # Zeros
-///
-/// If the hash happens to be zero, it is mapped to `DEFAULT_HASH`.
-#[inline(always)]
-#[must_use]
-pub const fn combine_hashes(a: u64, b: u64) -> u64 {
-    match a ^ b {
-        0 => ALT_ZERO_HASH,
-        r => r,
-    }
-}
diff --git a/src/func/mod.rs b/src/func/mod.rs
index 8298a63e..6120764d 100644
--- a/src/func/mod.rs
+++ b/src/func/mod.rs
@@ -13,15 +13,15 @@ pub mod script;
 
 pub use args::FuncArgs;
 pub use builtin::{get_builtin_binary_op_fn, get_builtin_op_assignment_fn};
-#[cfg(not(feature = "no_module"))]
-pub use call::gen_qualified_fn_call_signature;
-pub use call::{gen_fn_call_signature, FnCallArgs};
+#[cfg(not(feature = "no_closure"))]
+pub use call::ensure_no_data_race;
+#[cfg(not(feature = "no_function"))]
+pub use call::is_anonymous_fn;
+pub use call::FnCallArgs;
 pub use callable_function::CallableFunction;
 #[cfg(not(feature = "no_function"))]
 pub use func::Func;
-pub use hashing::{
-    calc_fn_hash, calc_fn_params_hash, calc_var_hash, combine_hashes, get_hasher, StraightHashMap,
-};
+pub use hashing::{calc_fn_hash, calc_fn_hash_full, calc_var_hash, get_hasher, StraightHashMap};
 pub use native::{
     locked_read, locked_write, shared_get_mut, shared_make_mut, shared_take, shared_take_or_clone,
     shared_try_take, FnAny, FnPlugin, IteratorFn, Locked, NativeCallContext, SendSync, Shared,
diff --git a/src/func/native.rs b/src/func/native.rs
index 6afda4da..912f9d79 100644
--- a/src/func/native.rs
+++ b/src/func/native.rs
@@ -4,7 +4,7 @@ use super::call::FnCallArgs;
 use crate::ast::FnCallHashes;
 use crate::eval::{Caches, GlobalRuntimeState};
 use crate::plugin::PluginFunction;
-use crate::tokenizer::{Token, TokenizeState};
+use crate::tokenizer::{is_valid_function_name, Token, TokenizeState};
 use crate::types::dynamic::Variant;
 use crate::{
     calc_fn_hash, Dynamic, Engine, EvalContext, FuncArgs, Module, Position, RhaiResult,
@@ -329,7 +329,12 @@ impl<'a> NativeCallContext<'a> {
         is_method_call: bool,
         args: &mut [&mut Dynamic],
     ) -> RhaiResult {
-        self._call_fn_raw(fn_name, false, is_ref_mut, is_method_call, args)
+        let name = fn_name.as_ref();
+        let native_only = !is_valid_function_name(name);
+        #[cfg(not(feature = "no_function"))]
+        let native_only = native_only && !crate::parser::is_anonymous_fn(name);
+
+        self._call_fn_raw(fn_name, native_only, is_ref_mut, is_method_call, args)
     }
     /// Call a registered native Rust function inside the call context.
     ///
@@ -377,22 +382,24 @@ impl<'a> NativeCallContext<'a> {
         let caches = &mut Caches::new();
 
         let fn_name = fn_name.as_ref();
+        let op_token = Token::lookup_symbol_from_syntax(fn_name);
+        let op_token = op_token.as_ref();
         let args_len = args.len();
 
         if native_only {
             return self
                 .engine()
-                .call_native_fn(
+                .exec_native_fn_call(
                     global,
                     caches,
                     self.lib,
+                    self.level + 1,
                     fn_name,
+                    op_token,
                     calc_fn_hash(None, fn_name, args_len),
                     args,
                     is_ref_mut,
-                    false,
                     Position::NONE,
-                    self.level + 1,
                 )
                 .map(|(r, ..)| r);
         }
@@ -411,18 +418,18 @@ impl<'a> NativeCallContext<'a> {
 
         self.engine()
             .exec_fn_call(
-                None,
                 global,
                 caches,
                 self.lib,
+                self.level + 1,
+                None,
                 fn_name,
-                false,
+                op_token,
                 hash,
                 args,
                 is_ref_mut,
                 is_method_call,
                 Position::NONE,
-                self.level + 1,
             )
             .map(|(r, ..)| r)
     }
diff --git a/src/func/script.rs b/src/func/script.rs
index 476343af..b80d74ae 100644
--- a/src/func/script.rs
+++ b/src/func/script.rs
@@ -24,16 +24,16 @@ impl Engine {
     /// **DO NOT** reuse the argument values unless for the first `&mut` argument - all others are silently replaced by `()`!
     pub(crate) fn call_script_fn(
         &self,
-        scope: &mut Scope,
         global: &mut GlobalRuntimeState,
         caches: &mut Caches,
         lib: &[&Module],
+        level: usize,
+        scope: &mut Scope,
         this_ptr: &mut Option<&mut Dynamic>,
         fn_def: &ScriptFnDef,
         args: &mut FnCallArgs,
         rewind_scope: bool,
         pos: Position,
-        level: usize,
     ) -> RhaiResult {
         #[cold]
         #[inline(never)]
@@ -140,20 +140,20 @@ impl Engine {
         #[cfg(feature = "debugging")]
         {
             let node = crate::ast::Stmt::Noop(fn_def.body.position());
-            self.run_debugger(scope, global, lib, this_ptr, &node, level)?;
+            self.run_debugger(global, caches, lib, level, scope, this_ptr, &node)?;
         }
 
         // Evaluate the function
         let mut _result = self
             .eval_stmt_block(
-                scope,
                 global,
                 caches,
                 lib,
+                level,
+                scope,
                 this_ptr,
                 &fn_def.body,
                 rewind_scope,
-                level,
             )
             .or_else(|err| match *err {
                 // Convert return statement to return value
@@ -190,7 +190,9 @@ impl Engine {
                     Ok(ref r) => crate::eval::DebuggerEvent::FunctionExitWithValue(r),
                     Err(ref err) => crate::eval::DebuggerEvent::FunctionExitWithError(err),
                 };
-                match self.run_debugger_raw(scope, global, lib, this_ptr, node, event, level) {
+                match self
+                    .run_debugger_raw(global, caches, lib, level, scope, this_ptr, node, event)
+                {
                     Ok(_) => (),
                     Err(err) => _result = Err(err),
                 }
diff --git a/src/lib.rs b/src/lib.rs
index 8879012f..12f36850 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -238,7 +238,7 @@ pub use func::Shared;
 /// Alias to [`RefCell`][std::cell::RefCell] or [`RwLock`][std::sync::RwLock] depending on the `sync` feature flag.
 pub use func::Locked;
 
-use func::{calc_fn_hash, calc_fn_params_hash, calc_var_hash, combine_hashes};
+use func::{calc_fn_hash, calc_fn_hash_full, calc_var_hash};
 
 pub use rhai_codegen::*;
 
diff --git a/src/module/mod.rs b/src/module/mod.rs
index 59ead075..6cb59198 100644
--- a/src/module/mod.rs
+++ b/src/module/mod.rs
@@ -9,8 +9,8 @@ use crate::func::{
 };
 use crate::types::{dynamic::Variant, BloomFilterU64, CustomTypesCollection};
 use crate::{
-    calc_fn_hash, calc_fn_params_hash, combine_hashes, Dynamic, Identifier, ImmutableString,
-    NativeCallContext, RhaiResultOf, Shared, SmartString, StaticVec,
+    calc_fn_hash, calc_fn_hash_full, Dynamic, Identifier, ImmutableString, NativeCallContext,
+    RhaiResultOf, Shared, SmartString, StaticVec,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -150,9 +150,10 @@ pub fn calc_native_fn_hash<'a>(
     fn_name: &str,
     params: &[TypeId],
 ) -> u64 {
-    let hash_script = calc_fn_hash(modules, fn_name, params.len());
-    let hash_params = calc_fn_params_hash(params.iter().copied());
-    combine_hashes(hash_script, hash_params)
+    calc_fn_hash_full(
+        calc_fn_hash(modules, fn_name, params.len()),
+        params.iter().copied(),
+    )
 }
 
 /// A module which may contain variables, sub-modules, external Rust functions,
@@ -1027,8 +1028,7 @@ impl Module {
 
         let name = name.as_ref();
         let hash_script = calc_fn_hash(None, name, param_types.len());
-        let hash_params = calc_fn_params_hash(param_types.iter().copied());
-        let hash_fn = combine_hashes(hash_script, hash_params);
+        let hash_fn = calc_fn_hash_full(hash_script, param_types.iter().copied());
 
         if is_dynamic {
             self.dynamic_functions_filter.mark(hash_script);
@@ -1984,7 +1984,9 @@ impl Module {
         let orig_constants = std::mem::take(&mut global.constants);
 
         // Run the script
-        let result = engine.eval_ast_with_scope_raw(&mut scope, global, ast, 0);
+        let caches = &mut crate::eval::Caches::new();
+
+        let result = engine.eval_ast_with_scope_raw(global, caches, 0, &mut scope, ast);
 
         // Create new module
         let mut module = Module::new();
diff --git a/src/optimizer.rs b/src/optimizer.rs
index 08abb8f2..4428c6da 100644
--- a/src/optimizer.rs
+++ b/src/optimizer.rs
@@ -11,8 +11,8 @@ use crate::func::hashing::get_hasher;
 use crate::tokenizer::Token;
 use crate::types::dynamic::AccessMode;
 use crate::{
-    calc_fn_hash, calc_fn_params_hash, combine_hashes, Dynamic, Engine, FnPtr, Identifier,
-    ImmutableString, Position, Scope, StaticVec, AST, INT,
+    calc_fn_hash, calc_fn_hash_full, Dynamic, Engine, FnPtr, Identifier, ImmutableString, Position,
+    Scope, StaticVec, AST, INT,
 };
 #[cfg(feature = "no_std")]
 use std::prelude::v1::*;
@@ -139,6 +139,7 @@ impl<'a> OptimizerState<'a> {
     pub fn call_fn_with_constant_arguments(
         &mut self,
         fn_name: &str,
+        op_token: Option<&Token>,
         arg_values: &mut [Dynamic],
     ) -> Option<Dynamic> {
         #[cfg(not(feature = "no_function"))]
@@ -147,17 +148,17 @@ impl<'a> OptimizerState<'a> {
         let lib = &[];
 
         self.engine
-            .call_native_fn(
+            .exec_native_fn_call(
                 &mut self.global,
                 &mut self.caches,
                 lib,
+                0,
                 fn_name,
+                op_token,
                 calc_fn_hash(None, fn_name, arg_values.len()),
                 &mut arg_values.iter_mut().collect::<StaticVec<_>>(),
                 false,
-                false,
                 Position::NONE,
-                0,
             )
             .ok()
             .map(|(v, ..)| v)
@@ -170,8 +171,7 @@ fn has_native_fn_override(
     hash_script: u64,
     arg_types: impl AsRef<[TypeId]>,
 ) -> bool {
-    let hash_params = calc_fn_params_hash(arg_types.as_ref().iter().copied());
-    let hash = combine_hashes(hash_script, hash_params);
+    let hash = calc_fn_hash_full(hash_script, arg_types.as_ref().iter().copied());
 
     // First check the global namespace and packages, but skip modules that are standard because
     // they should never conflict with system functions.
@@ -438,15 +438,15 @@ fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: b
             if !x.0.is_op_assignment()
                 && x.1.lhs.is_variable_access(true)
                 && matches!(&x.1.rhs, Expr::FnCall(x2, ..)
-                        if Token::lookup_from_syntax(&x2.name).map_or(false, |t| t.has_op_assignment())
+                        if Token::lookup_symbol_from_syntax(&x2.name).map_or(false, |t| t.has_op_assignment())
                         && x2.args.len() == 2
                         && x2.args[0].get_variable_name(true) == x.1.lhs.get_variable_name(true)
                 ) =>
         {
             match x.1.rhs {
-                Expr::FnCall(ref mut x2, ..) => {
+                Expr::FnCall(ref mut x2, pos) => {
                     state.set_dirty();
-                    x.0 = OpAssignment::new_op_assignment_from_base(&x2.name, x2.pos);
+                    x.0 = OpAssignment::new_op_assignment_from_base(&x2.name, pos);
                     x.1.rhs = mem::take(&mut x2.args[1]);
                 }
                 ref expr => unreachable!("Expr::FnCall expected but gets {:?}", expr),
@@ -1098,7 +1098,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
             && state.optimization_level == OptimizationLevel::Simple // simple optimizations
             && x.args.len() == 1
             && x.name == KEYWORD_FN_PTR
-            && x.args[0].is_constant()
+            && x.constant_args()
         => {
             let fn_name = match x.args[0] {
                 Expr::StringConstant(ref s, ..) => s.clone().into(),
@@ -1122,8 +1122,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
         Expr::FnCall(x, pos)
                 if !x.is_qualified() // Non-qualified
                 && state.optimization_level == OptimizationLevel::Simple // simple optimizations
-                && x.args.iter().all(Expr::is_constant) // all arguments are constants
-                //&& !is_valid_identifier(x.chars()) // cannot be scripted
+                && x.constant_args() // all arguments are constants
         => {
             let arg_values = &mut x.args.iter().map(|e| e.get_literal_value().unwrap()).collect::<StaticVec<_>>();
             let arg_types: StaticVec<_> = arg_values.iter().map(Dynamic::type_id).collect();
@@ -1142,8 +1141,8 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                     return;
                 }
                 // Overloaded operators can override built-in.
-                _ if x.args.len() == 2 && x.operator_token.is_some() && (state.engine.fast_operators() || !has_native_fn_override(state.engine, x.hashes.native, &arg_types)) => {
-                    if let Some(result) = get_builtin_binary_op_fn(x.operator_token.as_ref().unwrap(), &arg_values[0], &arg_values[1])
+                _ if x.args.len() == 2 && x.op_token.is_some() && (state.engine.fast_operators() || !has_native_fn_override(state.engine, x.hashes.native(), &arg_types)) => {
+                    if let Some(result) = get_builtin_binary_op_fn(x.op_token.as_ref().unwrap(), &arg_values[0], &arg_values[1])
                         .and_then(|f| {
                             #[cfg(not(feature = "no_function"))]
                             let lib = state.lib;
@@ -1186,11 +1185,11 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
         Expr::FnCall(x, pos)
                 if !x.is_qualified() // non-qualified
                 && state.optimization_level == OptimizationLevel::Full // full optimizations
-                && x.args.iter().all(Expr::is_constant) // all arguments are constants
+                && x.constant_args() // all arguments are constants
         => {
             // First search for script-defined functions (can override built-in)
             #[cfg(not(feature = "no_function"))]
-            let has_script_fn = state.lib.iter().find_map(|&m| m.get_script_fn(&x.name, x.args.len())).is_some();
+            let has_script_fn = !x.hashes.is_native_only() && state.lib.iter().find_map(|&m| m.get_script_fn(&x.name, x.args.len())).is_some();
             #[cfg(feature = "no_function")]
             let has_script_fn = false;
 
@@ -1201,7 +1200,7 @@ fn optimize_expr(expr: &mut Expr, state: &mut OptimizerState, _chaining: bool) {
                     KEYWORD_TYPE_OF if arg_values.len() == 1 => Some(state.engine.map_type_name(arg_values[0].type_name()).into()),
                     #[cfg(not(feature = "no_closure"))]
                     crate::engine::KEYWORD_IS_SHARED if arg_values.len() == 1 => Some(Dynamic::FALSE),
-                    _ => state.call_fn_with_constant_arguments(&x.name, arg_values)
+                    _ => state.call_fn_with_constant_arguments(&x.name, x.op_token.as_ref(), arg_values)
                 };
 
                 if let Some(result) = result {
diff --git a/src/parser.rs b/src/parser.rs
index c2e02aa7..f0c3843f 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -174,7 +174,7 @@ impl<'e> ParseState<'e> {
     ///
     /// # Return value: `(index, is_func_name)`
     ///
-    /// * `index`: `None` when the variable name is not found in the `stack`,
+    /// * `index`: [`None`] when the variable name is not found in the `stack`,
     ///            otherwise the index value.
     ///
     /// * `is_func_name`: `true` if the variable is actually the name of a function
@@ -223,7 +223,7 @@ impl<'e> ParseState<'e> {
     /// Returns the offset to be deducted from `Stack::len`,
     /// i.e. the top element of the [`ParseState`] is offset 1.
     ///
-    /// Returns `None` when the variable name is not found in the [`ParseState`].
+    /// Returns [`None`] when the variable name is not found in the [`ParseState`].
     ///
     /// # Panics
     ///
@@ -469,7 +469,7 @@ fn parse_var_name(input: &mut TokenStream) -> ParseResult<(SmartString, Position
         // Variable name
         (Token::Identifier(s), pos) => Ok((*s, pos)),
         // Reserved keyword
-        (Token::Reserved(s), pos) if is_valid_identifier(s.chars()) => {
+        (Token::Reserved(s), pos) if is_valid_identifier(s.as_str()) => {
             Err(PERR::Reserved(s.to_string()).into_err(pos))
         }
         // Bad identifier
@@ -486,7 +486,7 @@ fn parse_symbol(input: &mut TokenStream) -> ParseResult<(SmartString, Position)>
         // Symbol
         (token, pos) if token.is_standard_symbol() => Ok((token.literal_syntax().into(), pos)),
         // Reserved symbol
-        (Token::Reserved(s), pos) if !is_valid_identifier(s.chars()) => Ok((*s, pos)),
+        (Token::Reserved(s), pos) if !is_valid_identifier(s.as_str()) => Ok((*s, pos)),
         // Bad symbol
         (Token::LexError(err), pos) => Err(err.into_err(pos)),
         // Not a symbol
@@ -599,9 +599,7 @@ impl Engine {
                 #[cfg(feature = "no_module")]
                 let hash = calc_fn_hash(None, &id, 0);
 
-                let is_valid_function_name = is_valid_function_name(&id);
-
-                let hashes = if is_valid_function_name {
+                let hashes = if is_valid_function_name(&id) {
                     hash.into()
                 } else {
                     FnCallHashes::from_native(hash)
@@ -612,14 +610,11 @@ impl Engine {
                 return Ok(FnCallExpr {
                     name: state.get_interned_string(id),
                     capture_parent_scope,
-                    operator_token: None,
-                    #[cfg(not(feature = "no_function"))]
-                    can_be_script: is_valid_function_name,
+                    op_token: None,
                     #[cfg(not(feature = "no_module"))]
                     namespace,
                     hashes,
                     args,
-                    pos: settings.pos,
                 }
                 .into_fn_call_expr(settings.pos));
             }
@@ -671,9 +666,7 @@ impl Engine {
                     #[cfg(feature = "no_module")]
                     let hash = calc_fn_hash(None, &id, args.len());
 
-                    let is_valid_function_name = is_valid_function_name(&id);
-
-                    let hashes = if is_valid_function_name {
+                    let hashes = if is_valid_function_name(&id) {
                         hash.into()
                     } else {
                         FnCallHashes::from_native(hash)
@@ -684,14 +677,11 @@ impl Engine {
                     return Ok(FnCallExpr {
                         name: state.get_interned_string(id),
                         capture_parent_scope,
-                        operator_token: None,
-                        #[cfg(not(feature = "no_function"))]
-                        can_be_script: is_valid_function_name,
+                        op_token: None,
                         #[cfg(not(feature = "no_module"))]
                         namespace,
                         hashes,
                         args,
-                        pos: settings.pos,
                     }
                     .into_fn_call_expr(settings.pos));
                 }
@@ -1012,7 +1002,7 @@ impl Engine {
                 (Token::InterpolatedString(..), pos) => {
                     return Err(PERR::PropertyExpected.into_err(pos))
                 }
-                (Token::Reserved(s), pos) if is_valid_identifier(s.chars()) => {
+                (Token::Reserved(s), pos) if is_valid_identifier(s.as_str()) => {
                     return Err(PERR::Reserved(s.to_string()).into_err(pos));
                 }
                 (Token::LexError(err), pos) => return Err(err.into_err(pos)),
@@ -1941,11 +1931,8 @@ impl Engine {
                             name: state.get_interned_string("-"),
                             hashes: FnCallHashes::from_native(calc_fn_hash(None, "-", 1)),
                             args,
-                            pos,
-                            operator_token: Some(token),
+                            op_token: Some(token),
                             capture_parent_scope: false,
-                            #[cfg(not(feature = "no_function"))]
-                            can_be_script: false,
                         }
                         .into_fn_call_expr(pos))
                     }
@@ -1973,11 +1960,8 @@ impl Engine {
                             name: state.get_interned_string("+"),
                             hashes: FnCallHashes::from_native(calc_fn_hash(None, "+", 1)),
                             args,
-                            pos,
-                            operator_token: Some(token),
+                            op_token: Some(token),
                             capture_parent_scope: false,
-                            #[cfg(not(feature = "no_function"))]
-                            can_be_script: false,
                         }
                         .into_fn_call_expr(pos))
                     }
@@ -1998,11 +1982,8 @@ impl Engine {
                     name: state.get_interned_string("!"),
                     hashes: FnCallHashes::from_native(calc_fn_hash(None, "!", 1)),
                     args,
-                    pos,
-                    operator_token: Some(token),
+                    op_token: Some(token),
                     capture_parent_scope: false,
-                    #[cfg(not(feature = "no_function"))]
-                    can_be_script: false,
                 }
                 .into_fn_call_expr(pos))
             }
@@ -2217,11 +2198,15 @@ impl Engine {
             // lhs.func(...)
             (lhs, Expr::FnCall(mut func, func_pos)) => {
                 // Recalculate hash
-                func.hashes = FnCallHashes::from_all(
-                    #[cfg(not(feature = "no_function"))]
-                    calc_fn_hash(None, &func.name, func.args.len()),
-                    calc_fn_hash(None, &func.name, func.args.len() + 1),
-                );
+                func.hashes = if is_valid_function_name(&func.name) {
+                    FnCallHashes::from_all(
+                        #[cfg(not(feature = "no_function"))]
+                        calc_fn_hash(None, &func.name, func.args.len()),
+                        calc_fn_hash(None, &func.name, func.args.len() + 1),
+                    )
+                } else {
+                    FnCallHashes::from_native(calc_fn_hash(None, &func.name, func.args.len() + 1))
+                };
 
                 let rhs = Expr::MethodCall(func, func_pos);
                 Ok(Expr::Dot(BinaryExpr { lhs, rhs }.into(), op_flags, op_pos))
@@ -2263,11 +2248,19 @@ impl Engine {
                     // lhs.func().dot_rhs or lhs.func()[idx_rhs]
                     Expr::FnCall(mut func, func_pos) => {
                         // Recalculate hash
-                        func.hashes = FnCallHashes::from_all(
-                            #[cfg(not(feature = "no_function"))]
-                            calc_fn_hash(None, &func.name, func.args.len()),
-                            calc_fn_hash(None, &func.name, func.args.len() + 1),
-                        );
+                        func.hashes = if is_valid_function_name(&func.name) {
+                            FnCallHashes::from_all(
+                                #[cfg(not(feature = "no_function"))]
+                                calc_fn_hash(None, &func.name, func.args.len()),
+                                calc_fn_hash(None, &func.name, func.args.len() + 1),
+                            )
+                        } else {
+                            FnCallHashes::from_native(calc_fn_hash(
+                                None,
+                                &func.name,
+                                func.args.len() + 1,
+                            ))
+                        };
 
                         let new_lhs = BinaryExpr {
                             lhs: Expr::MethodCall(func, func_pos),
@@ -2322,7 +2315,7 @@ impl Engine {
                     .get(&**c)
                     .copied()
                     .ok_or_else(|| PERR::Reserved(c.to_string()).into_err(*current_pos))?,
-                Token::Reserved(c) if !is_valid_identifier(c.chars()) => {
+                Token::Reserved(c) if !is_valid_identifier(c) => {
                     return Err(PERR::UnknownOperator(c.to_string()).into_err(*current_pos))
                 }
                 _ => current_op.precedence(),
@@ -2347,7 +2340,7 @@ impl Engine {
                     .get(&**c)
                     .copied()
                     .ok_or_else(|| PERR::Reserved(c.to_string()).into_err(*next_pos))?,
-                Token::Reserved(c) if !is_valid_identifier(c.chars()) => {
+                Token::Reserved(c) if !is_valid_identifier(c) => {
                     return Err(PERR::UnknownOperator(c.to_string()).into_err(*next_pos))
                 }
                 _ => next_op.precedence(),
@@ -2371,34 +2364,31 @@ impl Engine {
 
             let op = op_token.syntax();
             let hash = calc_fn_hash(None, &op, 2);
-            let is_function = is_valid_function_name(&op);
-            let operator_token = if is_function {
+            let is_valid_script_function = is_valid_function_name(&op);
+            let operator_token = if is_valid_script_function {
                 None
             } else {
                 Some(op_token.clone())
             };
 
-            let op_base = FnCallExpr {
-                #[cfg(not(feature = "no_module"))]
-                namespace: Default::default(),
-                name: state.get_interned_string(op.as_ref()),
-                hashes: FnCallHashes::from_native(hash),
-                args: StaticVec::new_const(),
-                pos,
-                operator_token,
-                capture_parent_scope: false,
-                #[cfg(not(feature = "no_function"))]
-                can_be_script: is_function,
-            };
-
             let mut args = StaticVec::new_const();
             args.push(root);
             args.push(rhs);
             args.shrink_to_fit();
 
+            let mut op_base = FnCallExpr {
+                #[cfg(not(feature = "no_module"))]
+                namespace: Default::default(),
+                name: state.get_interned_string(op.as_ref()),
+                hashes: FnCallHashes::from_native(hash),
+                args,
+                op_token: operator_token,
+                capture_parent_scope: false,
+            };
+
             root = match op_token {
                 // '!=' defaults to true when passed invalid operands
-                Token::NotEqualsTo => FnCallExpr { args, ..op_base }.into_fn_call_expr(pos),
+                Token::NotEqualsTo => op_base.into_fn_call_expr(pos),
 
                 // Comparison operators default to false when passed invalid operands
                 Token::EqualsTo
@@ -2406,61 +2396,36 @@ impl Engine {
                 | Token::LessThanEqualsTo
                 | Token::GreaterThan
                 | Token::GreaterThanEqualsTo => {
-                    let pos = args[0].start_position();
-                    FnCallExpr { args, ..op_base }.into_fn_call_expr(pos)
+                    let pos = op_base.args[0].start_position();
+                    op_base.into_fn_call_expr(pos)
                 }
 
                 Token::Or => {
-                    let rhs = args.pop().unwrap();
-                    let current_lhs = args.pop().unwrap();
-                    Expr::Or(
-                        BinaryExpr {
-                            lhs: current_lhs.ensure_bool_expr()?,
-                            rhs: rhs.ensure_bool_expr()?,
-                        }
-                        .into(),
-                        pos,
-                    )
+                    let rhs = op_base.args.pop().unwrap().ensure_bool_expr()?;
+                    let lhs = op_base.args.pop().unwrap().ensure_bool_expr()?;
+                    Expr::Or(BinaryExpr { lhs: lhs, rhs: rhs }.into(), pos)
                 }
                 Token::And => {
-                    let rhs = args.pop().unwrap();
-                    let current_lhs = args.pop().unwrap();
-                    Expr::And(
-                        BinaryExpr {
-                            lhs: current_lhs.ensure_bool_expr()?,
-                            rhs: rhs.ensure_bool_expr()?,
-                        }
-                        .into(),
-                        pos,
-                    )
+                    let rhs = op_base.args.pop().unwrap().ensure_bool_expr()?;
+                    let lhs = op_base.args.pop().unwrap().ensure_bool_expr()?;
+                    Expr::And(BinaryExpr { lhs: lhs, rhs: rhs }.into(), pos)
                 }
                 Token::DoubleQuestion => {
-                    let rhs = args.pop().unwrap();
-                    let current_lhs = args.pop().unwrap();
-                    Expr::Coalesce(
-                        BinaryExpr {
-                            lhs: current_lhs,
-                            rhs,
-                        }
-                        .into(),
-                        pos,
-                    )
+                    let rhs = op_base.args.pop().unwrap();
+                    let lhs = op_base.args.pop().unwrap();
+                    Expr::Coalesce(BinaryExpr { lhs, rhs }.into(), pos)
                 }
                 Token::In => {
                     // Swap the arguments
-                    let current_lhs = args.remove(0);
-                    let pos = current_lhs.start_position();
-                    args.push(current_lhs);
-                    args.shrink_to_fit();
+                    let lhs = op_base.args.remove(0);
+                    let pos = lhs.start_position();
+                    op_base.args.push(lhs);
+                    op_base.args.shrink_to_fit();
 
                     // Convert into a call to `contains`
-                    FnCallExpr {
-                        hashes: calc_fn_hash(None, OP_CONTAINS, 2).into(),
-                        args,
-                        name: state.get_interned_string(OP_CONTAINS),
-                        ..op_base
-                    }
-                    .into_fn_call_expr(pos)
+                    op_base.hashes = calc_fn_hash(None, OP_CONTAINS, 2).into();
+                    op_base.name = state.get_interned_string(OP_CONTAINS);
+                    op_base.into_fn_call_expr(pos)
                 }
 
                 #[cfg(not(feature = "no_custom_syntax"))]
@@ -2470,24 +2435,17 @@ impl Engine {
                         .get(s.as_str())
                         .map_or(false, Option::is_some) =>
                 {
-                    let hash = calc_fn_hash(None, &s, 2);
-                    let pos = args[0].start_position();
-
-                    FnCallExpr {
-                        hashes: if is_function {
-                            hash.into()
-                        } else {
-                            FnCallHashes::from_native(hash)
-                        },
-                        args,
-                        ..op_base
-                    }
-                    .into_fn_call_expr(pos)
+                    op_base.hashes = if is_valid_script_function {
+                        calc_fn_hash(None, &s, 2).into()
+                    } else {
+                        FnCallHashes::from_native(calc_fn_hash(None, &s, 2))
+                    };
+                    op_base.into_fn_call_expr(pos)
                 }
 
                 _ => {
-                    let pos = args[0].start_position();
-                    FnCallExpr { args, ..op_base }.into_fn_call_expr(pos)
+                    let pos = op_base.args[0].start_position();
+                    op_base.into_fn_call_expr(pos)
                 }
             };
         }
@@ -2951,12 +2909,12 @@ impl Engine {
             let mut this_ptr = None;
             let context = EvalContext::new(
                 self,
-                &mut state.stack,
                 &mut state.global,
                 None,
                 &[],
-                &mut this_ptr,
                 level,
+                &mut state.stack,
+                &mut this_ptr,
             );
 
             match filter(false, info, context) {
@@ -3729,11 +3687,8 @@ impl Engine {
                 num_externals + 1,
             )),
             args,
-            pos,
-            operator_token: None,
+            op_token: None,
             capture_parent_scope: false,
-            #[cfg(not(feature = "no_function"))]
-            can_be_script: false,
         }
         .into_fn_call_expr(pos);
 
diff --git a/src/tests.rs b/src/tests.rs
index 34186402..8bbef0d4 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -41,7 +41,7 @@ fn check_struct_sizes() {
             size_of::<ParseError>(),
             if cfg!(feature = "no_position") { 8 } else { 16 }
         );
-        assert_eq!(size_of::<EvalAltResult>(), 72);
+        assert_eq!(size_of::<EvalAltResult>(), 64);
         assert_eq!(
             size_of::<NativeCallContext>(),
             if cfg!(feature = "no_position") {
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 6aa0ec43..7dea89d9 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -799,9 +799,9 @@ impl Token {
         })
     }
 
-    /// Reverse lookup a token from a piece of syntax.
+    /// Reverse lookup a symbol token from a piece of syntax.
     #[must_use]
-    pub fn lookup_from_syntax(syntax: &str) -> Option<Self> {
+    pub fn lookup_symbol_from_syntax(syntax: &str) -> Option<Self> {
         use Token::*;
 
         Some(match syntax {
@@ -879,19 +879,11 @@ impl Token {
             "**" => PowerOf,
             "**=" => PowerOfAssign,
 
-            #[cfg(feature = "no_object")]
-            "?." => Reserved(Box::new(syntax.into())),
-            #[cfg(feature = "no_index")]
-            "?[" => Reserved(Box::new(syntax.into())),
-
             #[cfg(not(feature = "no_function"))]
             "fn" => Fn,
             #[cfg(not(feature = "no_function"))]
             "private" => Private,
 
-            #[cfg(feature = "no_function")]
-            "fn" | "private" => Reserved(Box::new(syntax.into())),
-
             #[cfg(not(feature = "no_module"))]
             "import" => Import,
             #[cfg(not(feature = "no_module"))]
@@ -899,31 +891,43 @@ impl Token {
             #[cfg(not(feature = "no_module"))]
             "as" => As,
 
+            _ => return None,
+        })
+    }
+
+    /// Is a piece of syntax a reserved keyword?
+    #[must_use]
+    pub fn is_reserved_keyword(syntax: &str) -> bool {
+        match syntax {
+            #[cfg(feature = "no_object")]
+            "?." => true,
+            #[cfg(feature = "no_index")]
+            "?[" => true,
+            #[cfg(feature = "no_function")]
+            "fn" | "private" => true,
             #[cfg(feature = "no_module")]
-            "import" | "export" | "as" => Reserved(Box::new(syntax.into())),
+            "import" | "export" | "as" => true,
 
             // List of reserved operators
             "===" | "!==" | "->" | "<-" | "?" | ":=" | ":;" | "~" | "!." | "::<" | "(*" | "*)"
-            | "#" | "#!" | "@" | "$" | "++" | "--" | "..." | "<|" | "|>" => {
-                Reserved(Box::new(syntax.into()))
-            }
+            | "#" | "#!" | "@" | "$" | "++" | "--" | "..." | "<|" | "|>" => true,
 
             // List of reserved keywords
             "public" | "protected" | "super" | "new" | "use" | "module" | "package" | "var"
             | "static" | "shared" | "with" | "is" | "goto" | "exit" | "match" | "case"
             | "default" | "void" | "null" | "nil" | "spawn" | "thread" | "go" | "sync"
-            | "async" | "await" | "yield" => Reserved(Box::new(syntax.into())),
+            | "async" | "await" | "yield" => true,
 
             KEYWORD_PRINT | KEYWORD_DEBUG | KEYWORD_TYPE_OF | KEYWORD_EVAL | KEYWORD_FN_PTR
             | KEYWORD_FN_PTR_CALL | KEYWORD_FN_PTR_CURRY | KEYWORD_THIS | KEYWORD_IS_DEF_VAR => {
-                Reserved(Box::new(syntax.into()))
+                true
             }
 
             #[cfg(not(feature = "no_function"))]
-            crate::engine::KEYWORD_IS_DEF_FN => Reserved(Box::new(syntax.into())),
+            crate::engine::KEYWORD_IS_DEF_FN => true,
 
-            _ => return None,
-        })
+            _ => false,
+        }
     }
 
     /// Is this token [`EOF`][Token::EOF]?
@@ -1708,11 +1712,11 @@ fn get_next_token_inner(
             // letter or underscore ...
             #[cfg(not(feature = "unicode-xid-ident"))]
             ('a'..='z' | '_' | 'A'..='Z', ..) => {
-                return Some(get_identifier(stream, pos, start_pos, c));
+                return Some(get_token_as_identifier(stream, pos, start_pos, c));
             }
             #[cfg(feature = "unicode-xid-ident")]
             (ch, ..) if unicode_xid::UnicodeXID::is_xid_start(ch) || ch == '_' => {
-                return Some(get_identifier(stream, pos, start_pos, c));
+                return Some(get_token_as_identifier(stream, pos, start_pos, c));
             }
 
             // " - string literal
@@ -2179,8 +2183,8 @@ fn get_next_token_inner(
     Some((Token::EOF, *pos))
 }
 
-/// Get the next identifier.
-fn get_identifier(
+/// Get the next token, parsing it as an identifier.
+fn get_token_as_identifier(
     stream: &mut impl InputStream,
     pos: &mut Position,
     start_pos: Position,
@@ -2199,13 +2203,13 @@ fn get_identifier(
         }
     }
 
-    let is_valid_identifier = is_valid_identifier(identifier.chars());
-
-    if let Some(token) = Token::lookup_from_syntax(&identifier) {
+    if let Some(token) = Token::lookup_symbol_from_syntax(&identifier) {
         return (token, start_pos);
+    } else if Token::is_reserved_keyword(&identifier) {
+        return (Token::Reserved(Box::new(identifier)), start_pos);
     }
 
-    if !is_valid_identifier {
+    if !is_valid_identifier(&identifier) {
         return (
             Token::LexError(LERR::MalformedIdentifier(identifier.to_string()).into()),
             start_pos,
@@ -2233,10 +2237,10 @@ pub fn is_keyword_function(name: &str) -> bool {
 /// _(internals)_ Is a text string a valid identifier?
 /// Exported under the `internals` feature only.
 #[must_use]
-pub fn is_valid_identifier(name: impl Iterator<Item = char>) -> bool {
+pub fn is_valid_identifier(name: &str) -> bool {
     let mut first_alphabetic = false;
 
-    for ch in name {
+    for ch in name.chars() {
         match ch {
             '_' => (),
             _ if is_id_first_alphabetic(ch) => first_alphabetic = true,
@@ -2254,7 +2258,7 @@ pub fn is_valid_identifier(name: impl Iterator<Item = char>) -> bool {
 #[inline(always)]
 #[must_use]
 pub fn is_valid_function_name(name: &str) -> bool {
-    is_valid_identifier(name.chars())
+    is_valid_identifier(name) && !is_keyword_function(name)
 }
 
 /// Is a character valid to start an identifier?
@@ -2433,7 +2437,7 @@ impl<'a> Iterator for TokenIterator<'a> {
                 (.., true) => unreachable!("no custom operators"),
                 // Reserved keyword that is not custom and disabled.
                 (token, false) if !self.engine.disabled_symbols.is_empty() && self.engine.disabled_symbols.contains(token) => {
-                    let msg = format!("reserved {} '{token}' is disabled", if is_valid_identifier(token.chars()) { "keyword"} else {"symbol"});
+                    let msg = format!("reserved {} '{token}' is disabled", if is_valid_identifier(token) { "keyword"} else {"symbol"});
                     Token::LexError(LERR::ImproperSymbol(s.to_string(), msg).into())
                 },
                 // Reserved keyword/operator that is not custom.
diff --git a/src/types/fn_ptr.rs b/src/types/fn_ptr.rs
index 8c5d4b1f..5938b7a6 100644
--- a/src/types/fn_ptr.rs
+++ b/src/types/fn_ptr.rs
@@ -1,6 +1,6 @@
 //! The `FnPtr` type.
 
-use crate::tokenizer::is_valid_identifier;
+use crate::tokenizer::is_valid_function_name;
 use crate::types::dynamic::Variant;
 use crate::{
     Dynamic, Engine, FuncArgs, ImmutableString, Module, NativeCallContext, Position, RhaiError,
@@ -106,7 +106,7 @@ impl FnPtr {
     #[inline(always)]
     #[must_use]
     pub fn is_anonymous(&self) -> bool {
-        self.name.starts_with(crate::engine::FN_ANONYMOUS)
+        crate::func::is_anonymous_fn(&self.name)
     }
     /// Call the function pointer with curried arguments (if any).
     /// The function may be script-defined (not available under `no_function`) or native Rust.
@@ -254,7 +254,7 @@ impl TryFrom<ImmutableString> for FnPtr {
 
     #[inline(always)]
     fn try_from(value: ImmutableString) -> RhaiResultOf<Self> {
-        if is_valid_identifier(value.chars()) {
+        if is_valid_function_name(&value) {
             Ok(Self {
                 name: value,
                 curry: StaticVec::new_const(),
diff --git a/src/types/parse_error.rs b/src/types/parse_error.rs
index d11a49c6..86fedfdf 100644
--- a/src/types/parse_error.rs
+++ b/src/types/parse_error.rs
@@ -238,7 +238,7 @@ impl fmt::Display for ParseErrorType {
             Self::AssignmentToInvalidLHS(s) => f.write_str(s),
 
             Self::LiteralTooLarge(typ, max) => write!(f, "{typ} exceeds the maximum limit ({max})"),
-            Self::Reserved(s) if is_valid_identifier(s.chars()) => write!(f, "'{s}' is a reserved keyword"),
+            Self::Reserved(s) if is_valid_identifier(s.as_str()) => write!(f, "'{s}' is a reserved keyword"),
             Self::Reserved(s) => write!(f, "'{s}' is a reserved symbol"),
             Self::UnexpectedEOF => f.write_str("Script is incomplete"),
             Self::WrongSwitchIntegerCase => f.write_str("Integer switch case cannot follow a range case"),