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LibJS: Implement proper Iterator records

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Instead of using plain objects as Iterator records, causes confusion
about the object itself actually being its [[Iterator]] slot, and
requires non-standard type conversion shenanigans fpr the [[NextValue]]
and [[Done]] internal slots,  implement a proper Iterator record struct
and use it throughout.

Also annotate the remaining Iterator AOs with spec comments while we're
here.
This commit is contained in:
Linus Groh 2022-01-09 19:12:24 +01:00
parent e141f1e976
commit 09a11fa6ea
17 changed files with 337 additions and 209 deletions
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125
Userland/Libraries/LibJS/Runtime/VM.cpp
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@ -197,18 +197,17 @@ ThrowCompletionOr<void> VM::binding_initialization(NonnullRefPtr<BindingPattern>
// BindingPattern : ArrayBindingPattern
else {
// 1. Let iteratorRecord be ? GetIterator(value).
auto* iterator = TRY(get_iterator(global_object, value));
auto iterator_done = false;
auto iterator_record = TRY(get_iterator(global_object, value));
// 2. Let result be IteratorBindingInitialization of ArrayBindingPattern with arguments iteratorRecord and environment.
auto result = iterator_binding_initialization(*target, iterator, iterator_done, environment, global_object);
auto result = iterator_binding_initialization(*target, iterator_record, environment, global_object);
// 3. If iteratorRecord.[[Done]] is false, return ? IteratorClose(iteratorRecord, result).
if (!iterator_done) {
if (!iterator_record.done) {
// iterator_close() always returns a Completion, which ThrowCompletionOr will interpret as a throw
// completion. So only return the result of iterator_close() if it is indeed a throw completion.
auto completion = result.is_throw_completion() ? result.release_error() : normal_completion({});
if (completion = iterator_close(*iterator, move(completion)); completion.is_error())
if (completion = iterator_close(global_object, iterator_record, move(completion)); completion.is_error())
return completion.release_error();
}
@ -311,7 +310,7 @@ ThrowCompletionOr<void> VM::property_binding_initialization(BindingPattern const
// 13.15.5.5 Runtime Semantics: IteratorDestructuringAssignmentEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-iteratordestructuringassignmentevaluation
// 8.5.3 Runtime Semantics: IteratorBindingInitialization, https://tc39.es/ecma262/#sec-runtime-semantics-iteratorbindinginitialization
ThrowCompletionOr<void> VM::iterator_binding_initialization(BindingPattern const& binding, Object* iterator, bool& iterator_done, Environment* environment, GlobalObject& global_object)
ThrowCompletionOr<void> VM::iterator_binding_initialization(BindingPattern const& binding, Iterator& iterator_record, Environment* environment, GlobalObject& global_object)
{
// FIXME: this method is nearly identical to destructuring assignment!
for (size_t i = 0; i < binding.entries.size(); i++) {
@ -328,51 +327,97 @@ ThrowCompletionOr<void> VM::iterator_binding_initialization(BindingPattern const
return TRY(member_expression->to_reference(interpreter(), global_object));
}));
// BindingRestElement : ... BindingIdentifier
// BindingRestElement : ... BindingPattern
if (entry.is_rest) {
VERIFY(i == binding.entries.size() - 1);
// 2. Let A be ! ArrayCreate(0).
auto* array = MUST(Array::create(global_object, 0));
while (!iterator_done) {
auto next_object_or_error = iterator_next(*iterator);
if (next_object_or_error.is_throw_completion()) {
iterator_done = true;
return JS::throw_completion(*next_object_or_error.release_error().value());
}
auto* next_object = next_object_or_error.release_value();
auto done_property = TRY(next_object->get(names.done));
if (done_property.to_boolean()) {
iterator_done = true;
// 3. Let n be 0.
// 4. Repeat,
while (true) {
ThrowCompletionOr<Object*> next { nullptr };
// a. If iteratorRecord.[[Done]] is false, then
if (!iterator_record.done) {
// i. Let next be IteratorStep(iteratorRecord).
next = iterator_step(global_object, iterator_record);
// ii. If next is an abrupt completion, set iteratorRecord.[[Done]] to true.
// iii. ReturnIfAbrupt(next).
if (next.is_error()) {
iterator_record.done = true;
return next.release_error();
}
// iv. If next is false, set iteratorRecord.[[Done]] to true.
if (!next.value())
iterator_record.done = true;
}
// b. If iteratorRecord.[[Done]] is true, then
if (iterator_record.done) {
// NOTE: Step i. and ii. are handled below.
break;
}
auto next_value = TRY(next_object->get(names.value));
array->indexed_properties().append(next_value);
// c. Let nextValue be IteratorValue(next).
auto next_value = iterator_value(global_object, *next.value());
// d. If nextValue is an abrupt completion, set iteratorRecord.[[Done]] to true.
// e. ReturnIfAbrupt(nextValue).
if (next_value.is_error()) {
iterator_record.done = true;
return next_value.release_error();
}
// f. Perform ! CreateDataPropertyOrThrow(A, ! ToString(𝔽(n)), nextValue).
array->indexed_properties().append(next_value.value());
// g. Set n to n + 1.
}
value = array;
} else if (!iterator_done) {
auto next_object_or_error = iterator_next(*iterator);
if (next_object_or_error.is_throw_completion()) {
iterator_done = true;
return JS::throw_completion(*next_object_or_error.release_error().value());
}
auto* next_object = next_object_or_error.release_value();
auto done_property = TRY(next_object->get(names.done));
if (done_property.to_boolean()) {
iterator_done = true;
value = js_undefined();
} else {
auto value_or_error = next_object->get(names.value);
if (value_or_error.is_throw_completion()) {
iterator_done = true;
return JS::throw_completion(*value_or_error.release_error().value());
}
value = value_or_error.release_value();
}
} else {
}
// SingleNameBinding : BindingIdentifier Initializer[opt]
// BindingElement : BindingPattern Initializer[opt]
else {
// 1. Let v be undefined.
value = js_undefined();
// 2. If iteratorRecord.[[Done]] is false, then
if (!iterator_record.done) {
// a. Let next be IteratorStep(iteratorRecord).
auto next = iterator_step(global_object, iterator_record);
// b. If next is an abrupt completion, set iteratorRecord.[[Done]] to true.
// c. ReturnIfAbrupt(next).
if (next.is_error()) {
iterator_record.done = true;
return next.release_error();
}
// d. If next is false, set iteratorRecord.[[Done]] to true.
if (!next.value()) {
iterator_record.done = true;
}
// e. Else,
else {
// i. Set v to IteratorValue(next).
auto value_or_error = iterator_value(global_object, *next.value());
// ii. If v is an abrupt completion, set iteratorRecord.[[Done]] to true.
// iii. ReturnIfAbrupt(v).
if (value_or_error.is_throw_completion()) {
iterator_record.done = true;
return value_or_error.release_error();
}
value = value_or_error.release_value();
}
}
// NOTE: Step 3. and 4. are handled below.
}
if (value.is_undefined() && entry.initializer) {