LibJS: Make AsyncFunctionStart and AsyncBlockStart templates

This will allow implementing a version of these functions that accepts a
JS::SafeFunction, which is needed for the implementation of
Array.fromAsync.

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp

@@ -754,7 +754,8 @@ void ECMAScriptFunctionObject::ordinary_call_bind_this(ExecutionContext& callee_
 }
 
 // 27.7.5.1 AsyncFunctionStart ( promiseCapability, asyncFunctionBody ), https://tc39.es/ecma262/#sec-async-functions-abstract-operations-async-function-start
-void async_function_start(VM& vm, PromiseCapability const& promise_capability, NonnullRefPtr<Statement const> const& async_function_body)
+template<typename T>
+void async_function_start(VM& vm, PromiseCapability const& promise_capability, T const& async_function_body)
 {
     // 1. Let runningContext be the running execution context.
     auto& running_context = vm.running_execution_context();
@@ -771,7 +772,8 @@ void async_function_start(VM& vm, PromiseCapability const& promise_capability, N
 }
 
 // 27.7.5.2 AsyncBlockStart ( promiseCapability, asyncBody, asyncContext ), https://tc39.es/ecma262/#sec-asyncblockstart
-void async_block_start(VM& vm, NonnullRefPtr<Statement const> const& async_body, PromiseCapability const& promise_capability, ExecutionContext& async_context)
+template<typename T>
+void async_block_start(VM& vm, T const& async_body, PromiseCapability const& promise_capability, ExecutionContext& async_context)
 {
     auto& realm = *vm.current_realm();
 
@@ -847,6 +849,9 @@ void async_block_start(VM& vm, NonnullRefPtr<Statement const> const& async_body,
     // 8. Return unused.
 }
 
+template void async_block_start(VM&, NonnullGCPtr<Statement const> const& async_body, PromiseCapability const&, ExecutionContext&);
+template void async_function_start(VM&, PromiseCapability const&, NonnullGCPtr<Statement const> const& async_function_body);
+
 // 10.2.1.4 OrdinaryCallEvaluateBody ( F, argumentsList ), https://tc39.es/ecma262/#sec-ordinarycallevaluatebody
 // 15.8.4 Runtime Semantics: EvaluateAsyncFunctionBody, https://tc39.es/ecma262/#sec-runtime-semantics-evaluatefunctionbody
 Completion ECMAScriptFunctionObject::ordinary_call_evaluate_body()

Userland/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.h

@@ -15,8 +15,11 @@
 
 namespace JS {
 
-void async_block_start(VM&, NonnullRefPtr<Statement const> const& parse_node, PromiseCapability const&, ExecutionContext&);
-void async_function_start(VM&, PromiseCapability const&, NonnullRefPtr<Statement const> const& async_function_body);
+template<typename T>
+void async_block_start(VM&, T const& async_body, PromiseCapability const&, ExecutionContext&);
+
+template<typename T>
+void async_function_start(VM&, PromiseCapability const&, T const& async_function_body);
 
 // 10.2 ECMAScript Function Objects, https://tc39.es/ecma262/#sec-ecmascript-function-objects
 class ECMAScriptFunctionObject final : public FunctionObject {

Userland/Libraries/LibJS/SourceTextModule.cpp

@@ -737,7 +737,7 @@ ThrowCompletionOr<void> SourceTextModule::execute_module(VM& vm, GCPtr<PromiseCa
         VERIFY(capability != nullptr);
 
         // b. Perform AsyncBlockStart(capability, module.[[ECMAScriptCode]], moduleContext).
-        async_block_start(vm, m_ecmascript_code, *capability, module_context);
+        async_block_start<NonnullRefPtr<Statement const>>(vm, m_ecmascript_code, *capability, module_context);
     }
 
     // 11. Return unused.