Skip prototype field definition for arrow function (#2388)

This Pull Request changes the following:

- Skip prototype field definition for arrow function
- Add `GetArrowFunction` opcode

boa_engine/src/builtins/function/mod.rs

@@ -616,7 +616,7 @@ impl BuiltInFunctionObject {
             let function_object = if generator {
                 crate::vm::create_generator_function_object(code, r#async, context)
             } else {
-                crate::vm::create_function_object(code, r#async, Some(prototype), context)
+                crate::vm::create_function_object(code, r#async, false, Some(prototype), context)
             };
 
             context.realm.environments.extend(environments);
@@ -647,7 +647,7 @@ impl BuiltInFunctionObject {
 
             let environments = context.realm.environments.pop_to_global();
             let function_object =
-                crate::vm::create_function_object(code, r#async, Some(prototype), context);
+                crate::vm::create_function_object(code, r#async, false, Some(prototype), context);
             context.realm.environments.extend(environments);
 
             Ok(function_object)

boa_engine/src/bytecompiler/mod.rs

@@ -2317,6 +2317,8 @@ impl<'b> ByteCompiler<'b> {
             self.emit(Opcode::GetGenerator, &[index]);
         } else if r#async {
             self.emit(Opcode::GetFunctionAsync, &[index]);
+        } else if arrow {
+            self.emit(Opcode::GetArrowFunction, &[index]);
         } else {
             self.emit(Opcode::GetFunction, &[index]);
         }

boa_engine/src/vm/code_block.rs

@@ -223,7 +223,8 @@ impl CodeBlock {
                 *pc += size_of::<u32>();
                 format!("{operand1}, {operand2}")
             }
-            Opcode::GetFunction
+            Opcode::GetArrowFunction
+            | Opcode::GetFunction
             | Opcode::GetFunctionAsync
             | Opcode::GetGenerator
             | Opcode::GetGeneratorAsync => {
@@ -458,6 +459,7 @@ impl ToInternedString for CodeBlock {
 pub(crate) fn create_function_object(
     code: Gc<CodeBlock>,
     r#async: bool,
+    arrow: bool,
     prototype: Option<JsObject>,
     context: &mut Context,
 ) -> JsObject {
@@ -551,7 +553,7 @@ pub(crate) fn create_function_object(
     constructor
         .define_property_or_throw(js_string!("name"), name_property, context)
         .expect("failed to define the name property of the function");
-    if !r#async {
+    if !r#async && !arrow {
         constructor
             .define_property_or_throw(js_string!("prototype"), prototype_property, context)
             .expect("failed to define the prototype property of the function");

boa_engine/src/vm/mod.rs

@@ -250,6 +250,7 @@ impl Context {
             Opcode::SuperCallDerived => SuperCallDerived::execute(self)?,
             Opcode::Case => Case::execute(self)?,
             Opcode::Default => Default::execute(self)?,
+            Opcode::GetArrowFunction => GetArrowFunction::execute(self)?,
             Opcode::GetFunction => GetFunction::execute(self)?,
             Opcode::GetFunctionAsync => GetFunctionAsync::execute(self)?,
             Opcode::GetGenerator => GetGenerator::execute(self)?,

boa_engine/src/vm/opcode/get/function.rs

@@ -3,6 +3,26 @@ use crate::{
     Context, JsResult,
 };
 
+/// `GetArrowFunction` implements the Opcode Operation for `Opcode::GetArrowFunction`
+///
+/// Operation:
+///  - Get arrow function from the pre-compiled inner functions.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub(crate) struct GetArrowFunction;
+
+impl Operation for GetArrowFunction {
+    const NAME: &'static str = "GetArrowFunction";
+    const INSTRUCTION: &'static str = "INST - GetArrowFunction";
+
+    fn execute(context: &mut Context) -> JsResult<ShouldExit> {
+        let index = context.vm.read::<u32>();
+        let code = context.vm.frame().code.functions[index as usize].clone();
+        let function = create_function_object(code, false, true, None, context);
+        context.vm.push(function);
+        Ok(ShouldExit::False)
+    }
+}
+
 /// `GetFunction` implements the Opcode Operation for `Opcode::GetFunction`
 ///
 /// Operation:
@@ -17,7 +37,7 @@ impl Operation for GetFunction {
     fn execute(context: &mut Context) -> JsResult<ShouldExit> {
         let index = context.vm.read::<u32>();
         let code = context.vm.frame().code.functions[index as usize].clone();
-        let function = create_function_object(code, false, None, context);
+        let function = create_function_object(code, false, false, None, context);
         context.vm.push(function);
         Ok(ShouldExit::False)
     }
@@ -37,7 +57,7 @@ impl Operation for GetFunctionAsync {
     fn execute(context: &mut Context) -> JsResult<ShouldExit> {
         let index = context.vm.read::<u32>();
         let code = context.vm.frame().code.functions[index as usize].clone();
-        let function = create_function_object(code, true, None, context);
+        let function = create_function_object(code, true, false, None, context);
         context.vm.push(function);
         Ok(ShouldExit::False)
     }

boa_engine/src/vm/opcode/mod.rs

@@ -1022,6 +1022,13 @@ pub enum Opcode {
     /// Stack: `value` **=>**
     Default,
 
+    /// Get arrow function from the pre-compiled inner functions.
+    ///
+    /// Operands: address: `u32`
+    ///
+    /// Stack: **=>** func
+    GetArrowFunction,
+
     /// Get function from the pre-compiled inner functions.
     ///
     /// Operands: address: `u32`
@@ -1441,6 +1448,7 @@ impl Opcode {
             Self::SuperCallDerived => SuperCallDerived::NAME,
             Self::Case => Case::NAME,
             Self::Default => Default::NAME,
+            Self::GetArrowFunction => GetArrowFunction::NAME,
             Self::GetFunction => GetFunction::NAME,
             Self::GetFunctionAsync => GetFunctionAsync::NAME,
             Self::GetGenerator => GetGenerator::NAME,
@@ -1588,6 +1596,7 @@ impl Opcode {
             Self::SuperCallDerived => SuperCallDerived::INSTRUCTION,
             Self::Case => Case::INSTRUCTION,
             Self::Default => Default::INSTRUCTION,
+            Self::GetArrowFunction => GetArrowFunction::INSTRUCTION,
             Self::GetFunction => GetFunction::INSTRUCTION,
             Self::GetFunctionAsync => GetFunctionAsync::INSTRUCTION,
             Self::GetGenerator => GetGenerator::INSTRUCTION,