Create a unique `PromiseCapability` on each async function call (#2846)

This Pull Request changes the following:

- Creates a new `PromiseCapability` after every async function call instead of sharing the same capability for all calls of the same async function.

boa_engine/src/builtins/function/mod.rs

@@ -42,7 +42,7 @@ use thin_vec::ThinVec;
 
 use std::{fmt, io::Read};
 
-use super::{promise::PromiseCapability, BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
+use super::{BuiltInBuilder, BuiltInConstructor, IntrinsicObject};
 
 pub(crate) mod arguments;
 #[cfg(test)]
@@ -189,9 +189,6 @@ pub(crate) enum FunctionKind {
         /// The `[[HomeObject]]` internal slot.
         home_object: Option<JsObject>,
 
-        /// The promise capability record of the async function.
-        promise_capability: PromiseCapability,
-
         /// The class object that this function is associated with.
         class_object: Option<JsObject>,
     },
@@ -270,14 +267,8 @@ unsafe impl Trace for FunctionKind {
                 }
                 mark(class_object);
             }
-            Self::Async { code, environments, home_object, promise_capability, class_object } => {
-                mark(code);
-                mark(environments);
-                mark(home_object);
-                mark(promise_capability);
-                mark(class_object);
-            }
-            Self::Generator { code, environments, home_object, class_object}
+            Self::Async { code, environments, home_object, class_object }
+            | Self::Generator { code, environments, home_object, class_object}
             | Self::AsyncGenerator { code, environments, home_object, class_object} => {
                 mark(code);
                 mark(environments);

boa_engine/src/vm/code_block.rs

@@ -608,18 +608,11 @@ pub(crate) fn create_function_object(
         .build();
 
     let function = if r#async {
-        let promise_capability = PromiseCapability::new(
-            &context.intrinsics().constructors().promise().constructor(),
-            context,
-        )
-        .expect("cannot  fail per spec");
-
         Function::new(
             FunctionKind::Async {
                 code,
                 environments: context.vm.environments.clone(),
                 home_object: None,
-                promise_capability,
                 class_object: None,
             },
             context.realm().clone(),
@@ -835,8 +828,7 @@ impl JsObject {
 
         let context = &mut ContextCleanupGuard::new(context, realm, active_function);
 
-        let (code, mut environments, class_object, promise_cap, async_, gen) =
-            match function_object.kind() {
+        let (code, mut environments, class_object, async_, gen) = match function_object.kind() {
             FunctionKind::Native {
                 function,
                 constructor,
@@ -869,7 +861,6 @@ impl JsObject {
                     code,
                     environments.clone(),
                     class_object.clone(),
-                        None,
                     false,
                     false,
                 )
@@ -878,14 +869,12 @@ impl JsObject {
             FunctionKind::Async {
                 code,
                 environments,
-                    promise_capability,
                 class_object,
                 ..
             } => (
                 code.clone(),
                 environments.clone(),
                 class_object.clone(),
-                    Some(promise_capability.clone()),
                 true,
                 false,
             ),
@@ -898,7 +887,6 @@ impl JsObject {
                 code.clone(),
                 environments.clone(),
                 class_object.clone(),
-                    None,
                 false,
                 true,
             ),
@@ -911,7 +899,6 @@ impl JsObject {
                 code.clone(),
                 environments.clone(),
                 class_object.clone(),
-                    None,
                 true,
                 true,
             ),
@@ -919,6 +906,14 @@ impl JsObject {
 
         drop(object);
 
+        let promise_capability = (async_ && !gen).then(|| {
+            PromiseCapability::new(
+                &context.intrinsics().constructors().promise().constructor(),
+                context,
+            )
+            .expect("cannot  fail per spec")
+        });
+
         std::mem::swap(&mut environments, &mut context.vm.environments);
 
         let lexical_this_mode = code.this_mode == ThisMode::Lexical;
@@ -1023,7 +1018,7 @@ impl JsObject {
         let mut frame = CallFrame::new(code)
             .with_param_count(param_count)
             .with_arg_count(arg_count);
-        frame.promise_capability = promise_cap.clone();
+        frame.promise_capability = promise_capability.clone();
 
         context.vm.push_frame(frame);
 
@@ -1036,8 +1031,8 @@ impl JsObject {
         std::mem::swap(&mut environments, &mut context.vm.environments);
         std::mem::swap(&mut context.vm.stack, &mut stack);
 
-        if let Some(promise_cap) = promise_cap {
-            Ok(promise_cap.promise().clone().into())
+        if let Some(promise_capability) = promise_capability {
+            Ok(promise_capability.promise().clone().into())
         } else if gen {
             result?;
             let proto = this_function_object