[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index b2736818f957c96b700bf01311d85a8b057f432d..d23e3ea1454c34df5c9b5a42267f70c05f31a4fd 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1868,6 +1868,22 @@ void JSObject::JSObjectShortPrint(StringStream* accumulator) {
       accumulator->Add("<JS Array[%u]>", static_cast<uint32_t>(length));
       break;
     }
+    case JS_BOUND_FUNCTION_TYPE: {
+      JSBoundFunction* bound_function = JSBoundFunction::cast(this);
+      Object* name = bound_function->name();
+      accumulator->Add("<JS BoundFunction");
+      if (name->IsString()) {
+        String* str = String::cast(name);
+        if (str->length() > 0) {
+          accumulator->Add(" ");
+          accumulator->Put(str);
+        }
+      }
+      accumulator->Add(
+          " (BoundTargetFunction %p)>",
+          reinterpret_cast<void*>(bound_function->bound_target_function()));
+      break;
+    }
     case JS_WEAK_MAP_TYPE: {
       accumulator->Add("<JS WeakMap>");
       break;
@@ -2407,12 +2423,16 @@ String* JSReceiver::class_name() {
 MaybeHandle<String> JSReceiver::BuiltinStringTag(Handle<JSReceiver> object) {
   Maybe<bool> is_array = Object::IsArray(object);
   MAYBE_RETURN(is_array, MaybeHandle<String>());
+  Isolate* const isolate = object->GetIsolate();
   if (is_array.FromJust()) {
-    return object->GetIsolate()->factory()->Array_string();
+    return isolate->factory()->Array_string();
+  }
+  if (object->IsCallable()) {
+    return isolate->factory()->Function_string();
   }
   // TODO(adamk): class_name() is expensive, replace with instance type
   // checks where possible.
-  return handle(object->class_name());
+  return handle(object->class_name(), isolate);
 }
 
 
@@ -10720,47 +10740,6 @@ Handle<LiteralsArray> LiteralsArray::New(Isolate* isolate,
 }
 
 
-// static
-Handle<BindingsArray> BindingsArray::New(Isolate* isolate,
-                                         Handle<TypeFeedbackVector> vector,
-                                         Handle<JSReceiver> bound_function,
-                                         Handle<Object> bound_this,
-                                         int number_of_bindings) {
-  Handle<FixedArray> bindings = isolate->factory()->NewFixedArray(
-      number_of_bindings + kFirstBindingIndex);
-  Handle<BindingsArray> casted_bindings = Handle<BindingsArray>::cast(bindings);
-  casted_bindings->set_feedback_vector(*vector);
-  casted_bindings->set_bound_function(*bound_function);
-  casted_bindings->set_bound_this(*bound_this);
-  return casted_bindings;
-}
-
-
-// static
-Handle<JSArray> BindingsArray::CreateBoundArguments(
-    Handle<BindingsArray> bindings) {
-  int bound_argument_count = bindings->bindings_count();
-  Factory* factory = bindings->GetIsolate()->factory();
-  Handle<FixedArray> arguments = factory->NewFixedArray(bound_argument_count);
-  bindings->CopyTo(kFirstBindingIndex, *arguments, 0, bound_argument_count);
-  return factory->NewJSArrayWithElements(arguments);
-}
-
-
-// static
-Handle<JSArray> BindingsArray::CreateRuntimeBindings(
-    Handle<BindingsArray> bindings) {
-  Factory* factory = bindings->GetIsolate()->factory();
-  // A runtime bindings array consists of
-  // [bound function, bound this, [arg0, arg1, ...]].
-  Handle<FixedArray> runtime_bindings =
-      factory->NewFixedArray(2 + bindings->bindings_count());
-  bindings->CopyTo(kBoundFunctionIndex, *runtime_bindings, 0,
-                   2 + bindings->bindings_count());
-  return factory->NewJSArrayWithElements(runtime_bindings);
-}
-
-
 int HandlerTable::LookupRange(int pc_offset, int* stack_depth_out,
                               CatchPrediction* prediction_out) {
   int innermost_handler = -1, innermost_start = -1;
@@ -10820,16 +10799,25 @@ bool String::LooksValid() {
 
 
 // static
-MaybeHandle<String> Name::ToFunctionName(Handle<Name> name) {
-  if (name->IsString()) return Handle<String>::cast(name);
+MaybeHandle<String> Name::ToFunctionName(Handle<Name> name,
+                                         Handle<String> prefix) {
   // ES6 section 9.2.11 SetFunctionName, step 4.
   Isolate* const isolate = name->GetIsolate();
-  Handle<Object> description(Handle<Symbol>::cast(name)->name(), isolate);
-  if (description->IsUndefined()) return isolate->factory()->empty_string();
   IncrementalStringBuilder builder(isolate);
-  builder.AppendCharacter('[');
-  builder.AppendString(Handle<String>::cast(description));
-  builder.AppendCharacter(']');
+  if (prefix->length() != 0) {
+    builder.AppendString(prefix);
+    builder.AppendCharacter(' ');
+  }
+  if (name->IsString()) {
+    builder.AppendString(Handle<String>::cast(name));
+  } else {
+    Handle<Object> description(Handle<Symbol>::cast(name)->name(), isolate);
+    if (!description->IsUndefined()) {
+      builder.AppendCharacter('[');
+      builder.AppendString(Handle<String>::cast(description));
+      builder.AppendCharacter(']');
+    }
+  }
   return builder.Finish();
 }
 
@@ -12823,6 +12811,7 @@ bool CanSubclassHaveInobjectProperties(InstanceType instance_type) {
     case JS_FUNCTION_TYPE:
       return true;
 
+    case JS_BOUND_FUNCTION_TYPE:
     case JS_PROXY_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
     case JS_GLOBAL_OBJECT_TYPE:
@@ -13091,6 +13080,13 @@ Handle<String> NativeCodeFunctionSourceString(
 
 
 // static
+Handle<String> JSBoundFunction::ToString(Handle<JSBoundFunction> function) {
+  Isolate* const isolate = function->GetIsolate();
+  return isolate->factory()->NewStringFromAsciiChecked(kNativeCodeSource);
+}
+
+
+// static
 Handle<String> JSFunction::ToString(Handle<JSFunction> function) {
   Isolate* const isolate = function->GetIsolate();
   Handle<SharedFunctionInfo> shared_info(function->shared(), isolate);