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LibJS: Add the CreateMappedArgumentsObject abstract operation

This patch adds a new ArgumentsObject class to represent what the spec
calls "Arguments Exotic Objects"

These are constructed by the new CreateMappedArgumentsObject when the
`arguments` identifier is resolved in a callee context.

The implementation is incomplete and doesn't yet support mapping of
the parameter variables to the indexed properties of `arguments`.
This commit is contained in:
Andreas Kling 2021-06-28 13:26:01 +02:00
parent a55cf08ef9
commit 2d4eb40f59
8 changed files with 95 additions and 10 deletions

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@ -26,6 +26,7 @@ set(SOURCES
Runtime/AggregateError.cpp
Runtime/AggregateErrorConstructor.cpp
Runtime/AggregateErrorPrototype.cpp
Runtime/ArgumentsObject.cpp
Runtime/Array.cpp
Runtime/ArrayBuffer.cpp
Runtime/ArrayBufferConstructor.cpp

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@ -11,6 +11,7 @@
#include <LibJS/Interpreter.h>
#include <LibJS/Parser.h>
#include <LibJS/Runtime/AbstractOperations.h>
#include <LibJS/Runtime/ArgumentsObject.h>
#include <LibJS/Runtime/Array.h>
#include <LibJS/Runtime/ArrayPrototype.h>
#include <LibJS/Runtime/BoundFunction.h>
@ -214,6 +215,9 @@ Object* create_unmapped_arguments_object(GlobalObject& global_object, Vector<Val
if (vm.exception())
return nullptr;
for (auto& argument : arguments)
object->indexed_properties().append(argument);
// 4. Perform DefinePropertyOrThrow(obj, "length", PropertyDescriptor { [[Value]]: 𝔽(len), [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
auto length = arguments.size();
object->define_property(vm.names.length, Value(length), Attribute::Writable | Attribute::Configurable);
@ -222,9 +226,6 @@ Object* create_unmapped_arguments_object(GlobalObject& global_object, Vector<Val
object->define_property(*vm.well_known_symbol_iterator(), global_object.array_prototype()->get(vm.names.values), Attribute::Writable | Attribute::Configurable);
for (auto& argument : arguments)
object->indexed_properties().append(argument);
// 8. Perform ! DefinePropertyOrThrow(obj, "callee", PropertyDescriptor { [[Get]]: %ThrowTypeError%, [[Set]]: %ThrowTypeError%, [[Enumerable]]: false, [[Configurable]]: false }).
object->define_accessor(vm.names.callee, global_object.throw_type_error_function(), global_object.throw_type_error_function(), 0);
if (vm.exception())
@ -233,4 +234,40 @@ Object* create_unmapped_arguments_object(GlobalObject& global_object, Vector<Val
return object;
}
// 10.4.4.7 CreateMappedArgumentsObject ( func, formals, argumentsList, env ), https://tc39.es/ecma262/#sec-createmappedargumentsobject
Object* create_mapped_arguments_object(GlobalObject& global_object, FunctionObject& function, Vector<FunctionNode::Parameter> const& formals, Vector<Value> const& arguments, EnvironmentRecord&)
{
// FIXME: This implementation is incomplete and doesn't support the actual identifier mappings yet.
(void)formals;
auto& vm = global_object.vm();
auto* object = vm.heap().allocate<ArgumentsObject>(global_object, global_object);
if (vm.exception())
return nullptr;
// 14. Let index be 0.
// 15. Repeat, while index < len,
// a. Let val be argumentsList[index].
// b . Perform ! CreateDataPropertyOrThrow(obj, ! ToString(𝔽(index)), val).
// c. Set index to index + 1.
for (auto& argument : arguments)
object->indexed_properties().append(argument);
// 16. Perform ! DefinePropertyOrThrow(obj, "length", PropertyDescriptor { [[Value]]: 𝔽(len), [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
auto length = arguments.size();
object->define_property(vm.names.length, Value(length), Attribute::Writable | Attribute::Configurable);
if (vm.exception())
return nullptr;
// 20. Perform ! DefinePropertyOrThrow(obj, @@iterator, PropertyDescriptor { [[Value]]: %Array.prototype.values%, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
object->define_property(*vm.well_known_symbol_iterator(), global_object.array_prototype()->get(vm.names.values), Attribute::Writable | Attribute::Configurable);
// 21. Perform ! DefinePropertyOrThrow(obj, "callee", PropertyDescriptor { [[Value]]: func, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }).
object->define_property(vm.names.callee, Value(&function), Attribute::Writable | Attribute::Configurable);
if (vm.exception())
return nullptr;
return object;
}
}

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@ -7,6 +7,7 @@
#pragma once
#include <AK/Forward.h>
#include <LibJS/AST.h>
#include <LibJS/Forward.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/Value.h>
@ -24,6 +25,7 @@ FunctionObject* species_constructor(GlobalObject&, Object const&, FunctionObject
GlobalObject* get_function_realm(GlobalObject&, FunctionObject const&);
Object* get_prototype_from_constructor(GlobalObject&, FunctionObject const& constructor, Object* (GlobalObject::*intrinsic_default_prototype)());
Object* create_unmapped_arguments_object(GlobalObject&, Vector<Value> const& arguments);
Object* create_mapped_arguments_object(GlobalObject&, FunctionObject&, Vector<FunctionNode::Parameter> const&, Vector<Value> const& arguments, EnvironmentRecord&);
enum class CallerMode {
Strict,

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@ -0,0 +1,26 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Runtime/ArgumentsObject.h>
#include <LibJS/Runtime/GlobalObject.h>
namespace JS {
ArgumentsObject::ArgumentsObject(GlobalObject& global_object)
: Object(*global_object.object_prototype())
{
}
void ArgumentsObject::initialize(GlobalObject& global_object)
{
Base::initialize(global_object);
}
ArgumentsObject::~ArgumentsObject()
{
}
}

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@ -0,0 +1,23 @@
/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibJS/Runtime/Object.h>
namespace JS {
class ArgumentsObject final : public Object {
JS_OBJECT(ArgumentsObject, Object);
public:
explicit ArgumentsObject(GlobalObject&);
virtual void initialize(GlobalObject&) override;
virtual ~ArgumentsObject() override;
};
}

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@ -108,6 +108,7 @@ public:
virtual bool is_global_object() const { return false; }
virtual bool is_proxy_object() const { return false; }
virtual bool is_native_function() const { return false; }
virtual bool is_ordinary_function_object() const { return false; }
// B.3.7 The [[IsHTMLDDA]] Internal Slot, https://tc39.es/ecma262/#sec-IsHTMLDDA-internal-slot
virtual bool is_htmldda() const { return false; }

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@ -41,6 +41,7 @@ protected:
virtual bool is_strict_mode() const final { return m_is_strict; }
private:
virtual bool is_ordinary_function_object() const { return true; }
virtual FunctionEnvironmentRecord* create_environment_record(FunctionObject&) override;
virtual void visit_edges(Visitor&) override;

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@ -372,13 +372,7 @@ Value VM::get_variable(const FlyString& name, GlobalObject& global_object)
if (context.function->is_strict_mode() || !context.function->has_simple_parameter_list()) {
context.arguments_object = create_unmapped_arguments_object(global_object, context.arguments);
} else {
// FIXME: This code path is completely ad-hoc.
context.arguments_object = Array::create(global_object);
context.arguments_object->put(names.callee, context.function);
for (auto argument : context.arguments) {
context.arguments_object->indexed_properties().append(argument);
}
context.arguments_object = create_mapped_arguments_object(global_object, *context.function, verify_cast<OrdinaryFunctionObject>(context.function)->parameters(), context.arguments, *lexical_environment());
}
}
return context.arguments_object;