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LibJS: Convert resolve_binding() to ThrowCompletionOr

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The spec has a note stating that resolve binding will always return a
reference whose [[ReferencedName]] field is name. However this is not
correct as the underlying method GetIdentifierReference may throw on
env.HasBinding(name) thus it can throw. However, there are some
scenarios where it cannot throw because the reference is known to exist
in that case we use MUST with a comment.
This commit is contained in:
davidot 2021-12-30 14:13:20 +01:00 • committed by Linus Groh
parent dfaa6c910c
commit 676554d3f8
8 changed files with 44 additions and 42 deletions
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50
Userland/Libraries/LibJS/Runtime/VM.cpp
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@ -237,7 +237,7 @@ ThrowCompletionOr<void> VM::property_binding_initialization(BindingPattern const
if (property.is_rest) {
Reference assignment_target;
if (auto identifier_ptr = property.name.get_pointer<NonnullRefPtr<Identifier>>()) {
assignment_target = resolve_binding((*identifier_ptr)->string(), environment);
assignment_target = TRY(resolve_binding((*identifier_ptr)->string(), environment));
} else if (auto member_ptr = property.alias.get_pointer<NonnullRefPtr<MemberExpression>>()) {
assignment_target = (*member_ptr)->to_reference(interpreter(), global_object);
} else {
@ -282,9 +282,7 @@ ThrowCompletionOr<void> VM::property_binding_initialization(BindingPattern const
if (property.name.has<NonnullRefPtr<Identifier>>() && property.alias.has<Empty>()) {
// FIXME: this branch and not taking this have a lot in common we might want to unify it more (like it was before).
auto& identifier = *property.name.get<NonnullRefPtr<Identifier>>();
auto reference = resolve_binding(identifier.string(), environment);
if (auto* thrown_exception = exception())
return JS::throw_completion(thrown_exception->value());
auto reference = TRY(resolve_binding(identifier.string(), environment));
auto value_to_assign = TRY(object->get(name));
if (property.initializer && value_to_assign.is_undefined()) {
@ -298,17 +296,15 @@ ThrowCompletionOr<void> VM::property_binding_initialization(BindingPattern const
continue;
}
Optional<Reference> reference_to_assign_to;
property.alias.visit(
[&](Empty) {},
[&](NonnullRefPtr<Identifier> const& identifier) {
reference_to_assign_to = resolve_binding(identifier->string(), environment);
auto reference_to_assign_to = TRY(property.alias.visit(
[&](Empty) -> ThrowCompletionOr<Optional<Reference>> { return Optional<Reference> {}; },
[&](NonnullRefPtr<Identifier> const& identifier) -> ThrowCompletionOr<Optional<Reference>> {
return TRY(resolve_binding(identifier->string(), environment));
},
[&](NonnullRefPtr<BindingPattern> const&) {},
[&](NonnullRefPtr<MemberExpression> const& member_expression) {
reference_to_assign_to = member_expression->to_reference(interpreter(), global_object);
});
[&](NonnullRefPtr<BindingPattern> const&) -> ThrowCompletionOr<Optional<Reference>> { return Optional<Reference> {}; },
[&](NonnullRefPtr<MemberExpression> const& member_expression) -> ThrowCompletionOr<Optional<Reference>> {
return member_expression->to_reference(interpreter(), global_object);
}));
if (auto* thrown_exception = exception())
return JS::throw_completion(thrown_exception->value());
@ -347,19 +343,15 @@ ThrowCompletionOr<void> VM::iterator_binding_initialization(BindingPattern const
auto& entry = binding.entries[i];
Value value;
Optional<Reference> assignment_target;
entry.alias.visit(
[&](Empty) {},
[&](NonnullRefPtr<Identifier> const& identifier) {
assignment_target = resolve_binding(identifier->string(), environment);
auto assignment_target = TRY(entry.alias.visit(
[&](Empty) -> ThrowCompletionOr<Optional<Reference>> { return Optional<Reference> {}; },
[&](NonnullRefPtr<Identifier> const& identifier) -> ThrowCompletionOr<Optional<Reference>> {
return TRY(resolve_binding(identifier->string(), environment));
},
[&](NonnullRefPtr<BindingPattern> const&) {},
[&](NonnullRefPtr<MemberExpression> const& member_expression) {
assignment_target = member_expression->to_reference(interpreter(), global_object);
});
if (auto* thrown_exception = exception())
return JS::throw_completion(thrown_exception->value());
[&](NonnullRefPtr<BindingPattern> const&) -> ThrowCompletionOr<Optional<Reference>> { return Optional<Reference> {}; },
[&](NonnullRefPtr<MemberExpression> const& member_expression) -> ThrowCompletionOr<Optional<Reference>> {
return member_expression->to_reference(interpreter(), global_object);
}));
if (entry.is_rest) {
VERIFY(i == binding.entries.size() - 1);
@ -456,7 +448,7 @@ Reference VM::get_identifier_reference(Environment* environment, FlyString name,
}
// 9.4.2 ResolveBinding ( name [ , env ] ), https://tc39.es/ecma262/#sec-resolvebinding
Reference VM::resolve_binding(FlyString const& name, Environment* environment)
ThrowCompletionOr<Reference> VM::resolve_binding(FlyString const& name, Environment* environment)
{
// 1. If env is not present or if env is undefined, then
if (!environment) {
@ -472,6 +464,10 @@ Reference VM::resolve_binding(FlyString const& name, Environment* environment)
// 4. Return ? GetIdentifierReference(env, name, strict).
return get_identifier_reference(environment, name, strict);
// NOTE: The spec says:
// Note: The result of ResolveBinding is always a Reference Record whose [[ReferencedName]] field is name.
// But this is not actually correct as GetIdentifierReference (or really the methods it calls) can throw.
}
// 7.3.33 InitializeInstanceElements ( O, constructor ), https://tc39.es/ecma262/#sec-initializeinstanceelements