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LibJS: Add the CreateMappedArgumentsObject abstract operation

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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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43
Userland/Libraries/LibJS/Runtime/AbstractOperations.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;
}
}