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serenity/Userland/Libraries/LibJS/Runtime/PromiseReaction.h
Linus Groh 9d0d3affd4 LibJS: Replace the custom unwind mechanism with completions :^)
This includes:

- Parsing proper LabelledStatements with try_parse_labelled_statement()
- Removing LabelableStatement
- Implementing the LoopEvaluation semantics via loop_evaluation() in
  each IterationStatement subclass; and IterationStatement evaluation
  via {For,ForIn,ForOf,ForAwaitOf,While,DoWhile}Statement::execute()
- Updating ReturnStatement, BreakStatement and ContinueStatement to
  return the appropriate completion types
- Basically reimplementing TryStatement and SwitchStatement according to
  the spec, using completions
- Honoring result completion types in AsyncBlockStart and
  OrdinaryCallEvaluateBody
- Removing any uses of the VM unwind mechanism - most importantly,
  VM::throw_exception() now exclusively sets an exception and no longer
  triggers any unwinding mechanism.
  However, we already did a good job updating all of LibWeb and userland
  applications to not use it, and the few remaining uses elsewhere don't
  rely on unwinding AFAICT.
2022-01-06 12:36:23 +01:00

73 lines
3.7 KiB
C++

/*
* Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/JobCallback.h>
#include <LibJS/Runtime/VM.h>
namespace JS {
// 27.2.1.1 PromiseCapability Records, https://tc39.es/ecma262/#sec-promisecapability-records
struct PromiseCapability {
Object* promise { nullptr };
FunctionObject* resolve { nullptr };
FunctionObject* reject { nullptr };
};
// 27.2.1.1.1 IfAbruptRejectPromise ( value, capability ), https://tc39.es/ecma262/#sec-ifabruptrejectpromise
#define TRY_OR_REJECT(vm, capability, expression) \
({ \
auto _temporary_try_or_reject_result = (expression); \
/* 1. If value is an abrupt completion, then */ \
if (_temporary_try_or_reject_result.is_error()) { \
vm.clear_exception(); \
\
/* a. Perform ? Call(capability.[[Reject]], undefined, « value.[[Value]] »). */ \
TRY(vm.call(*capability.reject, js_undefined(), *_temporary_try_or_reject_result.release_error().value())); \
\
/* b. Return capability.[[Promise]]. */ \
return capability.promise; \
} \
\
/* 2. Else if value is a Completion Record, set value to value.[[Value]]. */ \
_temporary_try_or_reject_result.release_value(); \
})
// 27.2.1.5 NewPromiseCapability ( C ), https://tc39.es/ecma262/#sec-newpromisecapability
ThrowCompletionOr<PromiseCapability> new_promise_capability(GlobalObject& global_object, Value constructor);
// 27.2.1.2 PromiseReaction Records, https://tc39.es/ecma262/#sec-promisereaction-records
class PromiseReaction final : public Cell {
public:
enum class Type {
Fulfill,
Reject,
};
static PromiseReaction* create(VM& vm, Type type, Optional<PromiseCapability> capability, Optional<JobCallback> handler)
{
return vm.heap().allocate_without_global_object<PromiseReaction>(type, capability, handler);
}
PromiseReaction(Type type, Optional<PromiseCapability> capability, Optional<JobCallback> handler);
virtual ~PromiseReaction() = default;
Type type() const { return m_type; }
const Optional<PromiseCapability>& capability() const { return m_capability; }
const Optional<JobCallback>& handler() const { return m_handler; }
private:
virtual const char* class_name() const override { return "PromiseReaction"; }
virtual void visit_edges(Visitor&) override;
Type m_type;
Optional<PromiseCapability> m_capability;
Optional<JobCallback> m_handler;
};
}