Reduce BTree sizes by boxing values.

src/engine.rs

@@ -558,7 +558,7 @@ pub struct FnResolutionCacheEntry {
 }
 
 /// A function resolution cache.
-pub type FnResolutionCache = BTreeMap<u64, Option<FnResolutionCacheEntry>>;
+pub type FnResolutionCache = BTreeMap<u64, Option<Box<FnResolutionCacheEntry>>>;
 
 /// _(INTERNALS)_ A type that holds all the current states of the [`Engine`].
 /// Exported under the `internals` feature only.
@@ -776,7 +776,7 @@ pub struct Engine {
     pub(crate) module_resolver: Box<dyn crate::ModuleResolver>,
 
     /// A map mapping type names to pretty-print names.
-    pub(crate) type_names: BTreeMap<Identifier, Identifier>,
+    pub(crate) type_names: BTreeMap<Identifier, Box<Identifier>>,
 
     /// An empty [`ImmutableString`] for cloning purposes.
     pub(crate) empty_string: ImmutableString,
@@ -786,7 +786,7 @@ pub struct Engine {
     /// A map containing custom keywords and precedence to recognize.
     pub(crate) custom_keywords: BTreeMap<Identifier, Option<Precedence>>,
     /// Custom syntax.
-    pub(crate) custom_syntax: BTreeMap<Identifier, CustomSyntax>,
+    pub(crate) custom_syntax: BTreeMap<Identifier, Box<CustomSyntax>>,
     /// Callback closure for resolving variable access.
     pub(crate) resolve_var: Option<OnVarCallback>,
 

src/engine_api.rs

@@ -265,7 +265,8 @@ impl Engine {
     #[inline(always)]
     pub fn register_type_with_name<T: Variant + Clone>(&mut self, name: &str) -> &mut Self {
         // Add the pretty-print type name into the map
-        self.type_names.insert(type_name::<T>().into(), name.into());
+        self.type_names
+            .insert(type_name::<T>().into(), Box::new(name.into()));
         self
     }
     /// Register an type iterator for an iterable type with the [`Engine`].

src/fn_call.rs

@@ -161,7 +161,7 @@ impl Engine {
         args: Option<&mut FnCallArgs>,
         allow_dynamic: bool,
         is_op_assignment: bool,
-    ) -> &'s Option<FnResolutionCacheEntry> {
+    ) -> &'s Option<Box<FnResolutionCacheEntry>> {
         let mut hash = if let Some(ref args) = args {
             let hash_params = calc_fn_params_hash(args.iter().map(|a| a.type_id()));
             combine_hashes(hash_script, hash_params)
@@ -222,7 +222,7 @@ impl Engine {
 
                     match func {
                         // Specific version found
-                        Some(f) => return Some(f),
+                        Some(f) => return Some(Box::new(f)),
 
                         // Stop when all permutations are exhausted
                         None if bitmask >= max_bitmask => {
@@ -250,6 +250,7 @@ impl Engine {
                                         },
                                     )
                                 }
+                                .map(Box::new)
                             });
                         }
 
@@ -311,7 +312,8 @@ impl Engine {
             is_op_assignment,
         );
 
-        if let Some(FnResolutionCacheEntry { func, source }) = func {
+        if let Some(f) = func {
+            let FnResolutionCacheEntry { func, source } = f.as_ref();
             assert!(func.is_native());
 
             // Calling pure function but the first argument is a reference?
@@ -717,10 +719,11 @@ impl Engine {
         };
 
         #[cfg(not(feature = "no_function"))]
-        if let Some(FnResolutionCacheEntry { func, source }) = hash_script.and_then(|hash| {
+        if let Some(f) = hash_script.and_then(|hash| {
             self.resolve_function(mods, state, lib, fn_name, hash, None, false, false)
                 .clone()
         }) {
+            let FnResolutionCacheEntry { func, source } = *f;
             // Script function call
             assert!(func.is_script());
 

src/module/mod.rs

@@ -48,7 +48,7 @@ impl Default for FnNamespace {
 #[derive(Debug, Clone)]
 pub struct FuncInfo {
     /// Function instance.
-    pub func: CallableFunction,
+    pub func: Shared<CallableFunction>,
     /// Function namespace.
     pub namespace: FnNamespace,
     /// Function access mode.
@@ -140,7 +140,7 @@ pub struct Module {
     functions: BTreeMap<u64, Box<FuncInfo>>,
     /// Flattened collection of all external Rust functions, native or scripted.
     /// including those in sub-modules.
-    all_functions: BTreeMap<u64, CallableFunction>,
+    all_functions: BTreeMap<u64, Shared<CallableFunction>>,
     /// Iterator functions, keyed by the type producing the iterator.
     type_iterators: BTreeMap<TypeId, IteratorFn>,
     /// Flattened collection of iterator functions, including those in sub-modules.
@@ -497,7 +497,7 @@ impl Module {
                 param_types: Default::default(),
                 #[cfg(feature = "metadata")]
                 param_names,
-                func: fn_def.into(),
+                func: Into::<CallableFunction>::into(fn_def).into(),
             }),
         );
         self.indexed = false;
@@ -721,7 +721,7 @@ impl Module {
                 param_types,
                 #[cfg(feature = "metadata")]
                 param_names,
-                func,
+                func: func.into(),
             }),
         );
 
@@ -1119,7 +1119,7 @@ impl Module {
     /// The [`u64`] hash is returned by the [`set_native_fn`][Module::set_native_fn] call.
     #[inline(always)]
     pub(crate) fn get_fn(&self, hash_fn: u64) -> Option<&CallableFunction> {
-        self.functions.get(&hash_fn).map(|f| &f.func)
+        self.functions.get(&hash_fn).map(|f| f.func.as_ref())
     }
 
     /// Does the particular namespace-qualified function exist in the [`Module`]?
@@ -1135,7 +1135,9 @@ impl Module {
     /// The [`u64`] hash is calculated by [`build_index`][Module::build_index].
     #[inline(always)]
     pub(crate) fn get_qualified_fn(&self, hash_qualified_fn: u64) -> Option<&CallableFunction> {
-        self.all_functions.get(&hash_qualified_fn)
+        self.all_functions
+            .get(&hash_qualified_fn)
+            .map(|f| f.as_ref())
     }
 
     /// Combine another [`Module`] into this [`Module`].
@@ -1486,7 +1488,7 @@ impl Module {
             module: &'a Module,
             path: &mut Vec<&'a str>,
             variables: &mut BTreeMap<u64, Dynamic>,
-            functions: &mut BTreeMap<u64, CallableFunction>,
+            functions: &mut BTreeMap<u64, Shared<CallableFunction>>,
             type_iterators: &mut BTreeMap<TypeId, IteratorFn>,
         ) -> bool {
             let mut contains_indexed_global_functions = false;

src/syntax.rs

@@ -230,13 +230,14 @@ impl Engine {
         new_vars: isize,
         func: impl Fn(&mut EvalContext, &[Expression]) -> RhaiResult + SendSync + 'static,
     ) -> &mut Self {
-        let syntax = CustomSyntax {
-            parse: Box::new(parse),
-            func: (Box::new(func) as Box<FnCustomSyntaxEval>).into(),
-            scope_delta: new_vars,
-        };
-
-        self.custom_syntax.insert(key.into(), syntax);
+        self.custom_syntax.insert(
+            key.into(),
+            Box::new(CustomSyntax {
+                parse: Box::new(parse),
+                func: (Box::new(func) as Box<FnCustomSyntaxEval>).into(),
+                scope_delta: new_vars,
+            }),
+        );
         self
     }
 }