Skip environment creation when possible for arrow functions

core/ast/src/expression/literal/object.rs

@@ -469,6 +469,13 @@ impl ObjectMethodDefinition {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the object method definition contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for ObjectMethodDefinition {

core/ast/src/function/arrow_function.rs

@@ -86,6 +86,13 @@ impl ArrowFunction {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the arrow function contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for ArrowFunction {

core/ast/src/function/async_arrow_function.rs

@@ -86,6 +86,13 @@ impl AsyncArrowFunction {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the function declaration contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for AsyncArrowFunction {

core/ast/src/function/async_function.rs

@@ -78,6 +78,13 @@ impl AsyncFunctionDeclaration {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the async function declaration contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for AsyncFunctionDeclaration {
@@ -207,6 +214,13 @@ impl AsyncFunctionExpression {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the async function expression contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for AsyncFunctionExpression {

core/ast/src/function/async_generator.rs

@@ -77,6 +77,13 @@ impl AsyncGeneratorDeclaration {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the async generator declaration contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for AsyncGeneratorDeclaration {
@@ -206,6 +213,13 @@ impl AsyncGeneratorExpression {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the async generator expression contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for AsyncGeneratorExpression {

core/ast/src/function/class.rs

@@ -748,6 +748,13 @@ impl ClassMethodDefinition {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the class method definition contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for ClassMethodDefinition {

core/ast/src/function/generator.rs

@@ -76,6 +76,13 @@ impl GeneratorDeclaration {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the generator declaration contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for GeneratorDeclaration {
@@ -205,6 +212,13 @@ impl GeneratorExpression {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the generator expression contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for GeneratorExpression {

core/ast/src/function/ordinary_function.rs

@@ -77,6 +77,13 @@ impl FunctionDeclaration {
     pub const fn scopes(&self) -> &FunctionScopes {
         &self.scopes
     }
+
+    /// Returns `true` if the function declaration contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
 }
 
 impl ToIndentedString for FunctionDeclaration {
@@ -207,6 +214,13 @@ impl FunctionExpression {
         &self.scopes
     }
 
+    /// Returns `true` if the function expression contains a direct call to `eval`.
+    #[inline]
+    #[must_use]
+    pub const fn contains_direct_eval(&self) -> bool {
+        self.contains_direct_eval
+    }
+
     /// Analyze the scope of the function expression.
     pub fn analyze_scope(&mut self, strict: bool, scope: &Scope, interner: &Interner) -> bool {
         if !collect_bindings(self, strict, false, scope, interner) {

core/ast/src/scope_analyzer.rs

@@ -16,8 +16,9 @@ use crate::{
         FunctionExpression, GeneratorDeclaration, GeneratorExpression,
     },
     operations::{
-        bound_names, lexically_declared_names, lexically_scoped_declarations, var_declared_names,
+        bound_names, contains, lexically_declared_names, lexically_scoped_declarations,
-        var_scoped_declarations, LexicallyScopedDeclaration, VarScopedDeclaration,
+        var_declared_names, var_scoped_declarations, ContainsSymbol, LexicallyScopedDeclaration,
+        VarScopedDeclaration,
     },
     property::PropertyName,
     scope::{FunctionScopes, IdentifierReference, Scope},
@@ -1171,11 +1172,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut FunctionDeclaration,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1183,11 +1187,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut GeneratorDeclaration,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1195,11 +1202,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut AsyncFunctionDeclaration,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1207,11 +1217,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut AsyncGeneratorDeclaration,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1219,11 +1232,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut FunctionExpression,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut node.name_scope,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1231,11 +1247,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut GeneratorExpression,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut node.name_scope,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1243,11 +1262,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut AsyncFunctionExpression,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut node.name_scope,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1255,11 +1277,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut AsyncGeneratorExpression,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut node.name_scope,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1267,11 +1292,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut ArrowFunction,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            true,
+            contains_direct_eval,
         )
     }
 
@@ -1279,11 +1307,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         &mut self,
         node: &'ast mut AsyncArrowFunction,
     ) -> ControlFlow<Self::BreakTy> {
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            true,
+            contains_direct_eval,
         )
     }
 
@@ -1338,12 +1369,17 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
         node: &'ast mut ClassElement,
     ) -> ControlFlow<Self::BreakTy> {
         match node {
-            ClassElement::MethodDefinition(node) => self.visit_function_like(
+            ClassElement::MethodDefinition(node) => {
+                let contains_direct_eval = node.contains_direct_eval();
+                self.visit_function_like(
                     &mut node.body,
                     &mut node.parameters,
                     &mut node.scopes,
                     &mut None,
-            ),
+                    false,
+                    contains_direct_eval,
+                )
+            }
             ClassElement::FieldDefinition(field) | ClassElement::StaticFieldDefinition(field) => {
                 try_break!(self.visit_property_name_mut(&mut field.name));
                 let index = self.index;
@@ -1371,12 +1407,17 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
                 }
                 ControlFlow::Continue(())
             }
-            ClassElement::StaticBlock(node) => self.visit_function_like(
+            ClassElement::StaticBlock(node) => {
+                let contains_direct_eval = contains(node.statements(), ContainsSymbol::DirectEval);
+                self.visit_function_like(
                     &mut node.body,
                     &mut FormalParameterList::default(),
                     &mut node.scopes,
                     &mut None,
-            ),
+                    false,
+                    contains_direct_eval,
+                )
+            }
         }
     }
 
@@ -1390,11 +1431,14 @@ impl<'ast> VisitorMut<'ast> for ScopeIndexVisitor {
                 try_break!(self.visit_expression_mut(name));
             }
         }
+        let contains_direct_eval = node.contains_direct_eval();
         self.visit_function_like(
             &mut node.body,
             &mut node.parameters,
             &mut node.scopes,
             &mut None,
+            false,
+            contains_direct_eval,
         )
     }
 
@@ -1531,6 +1575,8 @@ impl ScopeIndexVisitor {
         parameters: &mut FormalParameterList,
         scopes: &mut FunctionScopes,
         name_scope: &mut Option<Scope>,
+        arrow: bool,
+        contains_direct_eval: bool,
     ) -> ControlFlow<()> {
         let index = self.index;
         if let Some(scope) = name_scope {
@@ -1539,7 +1585,9 @@ impl ScopeIndexVisitor {
             }
             scope.set_index(self.index);
         }
+        if !(arrow && scopes.function_scope.all_bindings_local() && !contains_direct_eval) {
             self.index += 1;
+        }
         scopes.function_scope.set_index(self.index);
         if let Some(scope) = &scopes.parameters_eval_scope {
             if !scope.all_bindings_local() {

core/engine/src/builtins/function/mod.rs

@@ -655,6 +655,7 @@ impl BuiltInFunctionObject {
                 context.realm().scope().clone(),
                 context.realm().scope().clone(),
                 function.scopes(),
+                function.contains_direct_eval(),
                 context.interner_mut(),
             );
 
@@ -1026,10 +1027,12 @@ pub(crate) fn function_call(
         last_env += 1;
     }
 
+    if code.has_function_scope() {
         context.vm.environments.push_function(
             code.constant_scope(last_env),
             FunctionSlots::new(this, function_object.clone(), None),
         );
+    }
 
     Ok(CallValue::Ready)
 }

core/engine/src/bytecompiler/class.rs

@@ -96,6 +96,7 @@ impl ByteCompiler<'_> {
         compiler.code_block_flags |= CodeBlockFlags::IS_CLASS_CONSTRUCTOR;
 
         if let Some(expr) = &class.constructor {
+            compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
             let _ = compiler.push_scope(expr.scopes().function_scope());
 
             compiler.length = expr.parameters().length();
@@ -115,11 +116,13 @@ impl ByteCompiler<'_> {
             compiler.emit_opcode(Opcode::PushUndefined);
         } else if class.super_ref.is_some() {
             // We push an empty, unused function scope since the compiler expects a function scope.
+            compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
             let _ = compiler.push_scope(&Scope::new(compiler.lexical_scope.clone(), true));
             compiler.emit_opcode(Opcode::SuperCallDerived);
             compiler.emit_opcode(Opcode::BindThisValue);
         } else {
             // We push an empty, unused function scope since the compiler expects a function scope.
+            compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
             let _ = compiler.push_scope(&Scope::new(compiler.lexical_scope.clone(), true));
             compiler.emit_opcode(Opcode::PushUndefined);
         }
@@ -288,6 +291,7 @@ impl ByteCompiler<'_> {
                     );
 
                     // Function environment
+                    field_compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
                     let _ = field_compiler.push_scope(field.scope());
                     let is_anonymous_function = if let Some(node) = &field.field() {
                         field_compiler.compile_expr(node, true);
@@ -322,6 +326,7 @@ impl ByteCompiler<'_> {
                         self.interner,
                         self.in_with,
                     );
+                    field_compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
                     let _ = field_compiler.push_scope(field.scope());
                     if let Some(node) = field.field() {
                         field_compiler.compile_expr(node, true);
@@ -363,6 +368,7 @@ impl ByteCompiler<'_> {
                         self.interner,
                         self.in_with,
                     );
+                    field_compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
                     let _ = field_compiler.push_scope(field.scope());
                     let is_anonymous_function = if let Some(node) = &field.field() {
                         field_compiler.compile_expr(node, true);
@@ -406,6 +412,7 @@ impl ByteCompiler<'_> {
                         self.interner,
                         self.in_with,
                     );
+                    compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
                     let _ = compiler.push_scope(block.scopes().function_scope());
 
                     compiler.function_declaration_instantiation(

core/engine/src/bytecompiler/declarations.rs

@@ -479,7 +479,8 @@ impl ByteCompiler<'_> {
         // 16. For each Parse Node f of functionsToInitialize, do
         for function in functions_to_initialize {
             // a. Let fn be the sole element of the BoundNames of f.
-            let (name, generator, r#async, parameters, body, scopes) = match &function {
+            let (name, generator, r#async, parameters, body, scopes, contains_direct_eval) =
+                match &function {
                     VarScopedDeclaration::FunctionDeclaration(f) => (
                         f.name(),
                         false,
@@ -487,6 +488,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::GeneratorDeclaration(f) => (
                         f.name(),
@@ -495,6 +497,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::AsyncFunctionDeclaration(f) => (
                         f.name(),
@@ -503,6 +506,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::AsyncGeneratorDeclaration(f) => (
                         f.name(),
@@ -511,6 +515,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::VariableDeclaration(_) => continue,
                 };
@@ -527,6 +532,7 @@ impl ByteCompiler<'_> {
                     self.variable_scope.clone(),
                     self.lexical_scope.clone(),
                     &scopes,
+                    contains_direct_eval,
                     self.interner,
                 );
 
@@ -737,7 +743,8 @@ impl ByteCompiler<'_> {
         // 17. For each Parse Node f of functionsToInitialize, do
         for function in functions_to_initialize {
             // a. Let fn be the sole element of the BoundNames of f.
-            let (name, generator, r#async, parameters, body, scopes) = match &function {
+            let (name, generator, r#async, parameters, body, scopes, contains_direct_eval) =
+                match &function {
                     VarScopedDeclaration::FunctionDeclaration(f) => (
                         f.name(),
                         false,
@@ -745,6 +752,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::GeneratorDeclaration(f) => (
                         f.name(),
@@ -753,6 +761,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::AsyncFunctionDeclaration(f) => (
                         f.name(),
@@ -761,6 +770,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::AsyncGeneratorDeclaration(f) => (
                         f.name(),
@@ -769,6 +779,7 @@ impl ByteCompiler<'_> {
                         f.parameters(),
                         f.body(),
                         f.scopes().clone(),
+                        f.contains_direct_eval(),
                     ),
                     VarScopedDeclaration::VariableDeclaration(_) => {
                         continue;
@@ -788,6 +799,7 @@ impl ByteCompiler<'_> {
                     self.variable_scope.clone(),
                     self.lexical_scope.clone(),
                     &scopes,
+                    contains_direct_eval,
                     self.interner,
                 );
 

core/engine/src/bytecompiler/function.rs

@@ -94,6 +94,7 @@ impl FunctionCompiler {
     }
 
     /// Compile a function statement list and it's parameters into bytecode.
+    #[allow(clippy::too_many_arguments)]
     pub(crate) fn compile(
         mut self,
         parameters: &FormalParameterList,
@@ -101,6 +102,7 @@ impl FunctionCompiler {
         variable_environment: Scope,
         lexical_environment: Scope,
         scopes: &FunctionScopes,
+        contains_direct_eval: bool,
         interner: &mut Interner,
     ) -> Gc<CodeBlock> {
         self.strict = self.strict || body.strict();
@@ -134,8 +136,14 @@ impl FunctionCompiler {
                 let _ = compiler.push_scope(&scope);
             }
         }
-        // Function environment
+
+        if self.arrow && scopes.function_scope().all_bindings_local() && !contains_direct_eval {
+            compiler.variable_scope = scopes.function_scope().clone();
+            compiler.lexical_scope = scopes.function_scope().clone();
+        } else {
+            compiler.code_block_flags |= CodeBlockFlags::HAS_FUNCTION_SCOPE;
             let _ = compiler.push_scope(scopes.function_scope());
+        }
 
         // Taken from:
         //  - 15.9.3 Runtime Semantics: EvaluateAsyncConciseBody: <https://tc39.es/ecma262/#sec-runtime-semantics-evaluateasyncconcisebody>

core/engine/src/bytecompiler/mod.rs

@@ -122,6 +122,7 @@ pub(crate) struct FunctionSpec<'a> {
     body: &'a FunctionBody,
     pub(crate) scopes: &'a FunctionScopes,
     pub(crate) name_scope: Option<&'a Scope>,
+    pub(crate) contains_direct_eval: bool,
 }
 
 impl<'a> From<&'a FunctionDeclaration> for FunctionSpec<'a> {
@@ -133,6 +134,7 @@ impl<'a> From<&'a FunctionDeclaration> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -146,6 +148,7 @@ impl<'a> From<&'a GeneratorDeclaration> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -159,6 +162,7 @@ impl<'a> From<&'a AsyncFunctionDeclaration> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -172,6 +176,7 @@ impl<'a> From<&'a AsyncGeneratorDeclaration> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -185,6 +190,7 @@ impl<'a> From<&'a FunctionExpression> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: function.name_scope(),
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -198,6 +204,7 @@ impl<'a> From<&'a ArrowFunction> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -211,6 +218,7 @@ impl<'a> From<&'a AsyncArrowFunction> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: None,
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -224,6 +232,7 @@ impl<'a> From<&'a AsyncFunctionExpression> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: function.name_scope(),
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -237,6 +246,7 @@ impl<'a> From<&'a GeneratorExpression> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: function.name_scope(),
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -250,6 +260,7 @@ impl<'a> From<&'a AsyncGeneratorExpression> for FunctionSpec<'a> {
             body: function.body(),
             scopes: function.scopes(),
             name_scope: function.name_scope(),
+            contains_direct_eval: function.contains_direct_eval(),
         }
     }
 }
@@ -270,6 +281,7 @@ impl<'a> From<&'a ClassMethodDefinition> for FunctionSpec<'a> {
             body: method.body(),
             scopes: method.scopes(),
             name_scope: None,
+            contains_direct_eval: method.contains_direct_eval(),
         }
     }
 }
@@ -290,6 +302,7 @@ impl<'a> From<&'a ObjectMethodDefinition> for FunctionSpec<'a> {
             body: method.body(),
             scopes: method.scopes(),
             name_scope: None,
+            contains_direct_eval: method.contains_direct_eval(),
         }
     }
 }
@@ -1518,6 +1531,7 @@ impl<'ctx> ByteCompiler<'ctx> {
                 self.variable_scope.clone(),
                 self.lexical_scope.clone(),
                 scopes,
+                function.contains_direct_eval,
                 self.interner,
             );
 
@@ -1595,6 +1609,7 @@ impl<'ctx> ByteCompiler<'ctx> {
                 self.variable_scope.clone(),
                 self.lexical_scope.clone(),
                 scopes,
+                function.contains_direct_eval,
                 self.interner,
             );
 
@@ -1638,6 +1653,7 @@ impl<'ctx> ByteCompiler<'ctx> {
                 self.variable_scope.clone(),
                 self.lexical_scope.clone(),
                 scopes,
+                function.contains_direct_eval,
                 self.interner,
             );
 

core/engine/src/vm/code_block.rs

@@ -66,6 +66,9 @@ bitflags! {
         /// Arrow and method functions don't have `"prototype"` property.
         const HAS_PROTOTYPE_PROPERTY = 0b1000_0000;
 
+        /// If the function requires a function scope.
+        const HAS_FUNCTION_SCOPE = 0b1_0000_0000;
+
         /// Trace instruction execution to `stdout`.
         #[cfg(feature = "trace")]
         const TRACEABLE = 0b1000_0000_0000_0000;
@@ -271,6 +274,13 @@ impl CodeBlock {
             .contains(CodeBlockFlags::HAS_PROTOTYPE_PROPERTY)
     }
 
+    /// Returns true if this function requires a function scope.
+    pub(crate) fn has_function_scope(&self) -> bool {
+        self.flags
+            .get()
+            .contains(CodeBlockFlags::HAS_FUNCTION_SCOPE)
+    }
+
     /// Find exception [`Handler`] in the code block given the current program counter (`pc`).
     #[inline]
     pub(crate) fn find_handler(&self, pc: u32) -> Option<(usize, &Handler)> {