604d5f5bca
For example, consider cases where we want to propagate errors only in
specific instances:
auto result = read_data(); // something like ErrorOr<ByteBuffer>
if (result.is_error() && result.error().code() != EINTR)
continue;
auto bytes = TRY(result);
The TRY invocation will currently copy the byte buffer when the
expression (in this case, just a local variable) is stored into
_temporary_result.
This patch binds the expression to a reference to prevent such copies.
In less trival invocations (such as TRY(some_function()), this will
incur only temporary lifetime extensions, i.e. no functional change.
92 lines
6.4 KiB
C++
92 lines
6.4 KiB
C++
/*
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* Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Forward.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Runtime/AbstractOperations.h>
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namespace JS {
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// 27.2.1.1 PromiseCapability Records, https://tc39.es/ecma262/#sec-promisecapability-records
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class PromiseCapability final : public Cell {
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JS_CELL(PromiseCapability, Cell);
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public:
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static NonnullGCPtr<PromiseCapability> create(VM& vm, GCPtr<Object> promise, GCPtr<FunctionObject> resolve, GCPtr<FunctionObject> reject);
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virtual ~PromiseCapability() = default;
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[[nodiscard]] GCPtr<Object> promise() const { return m_promise; }
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void set_promise(NonnullGCPtr<Object> promise) { m_promise = promise; }
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[[nodiscard]] GCPtr<FunctionObject> resolve() const { return m_resolve; }
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void set_resolve(NonnullGCPtr<FunctionObject> resolve) { m_resolve = resolve; }
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[[nodiscard]] GCPtr<FunctionObject> reject() const { return m_reject; }
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void set_reject(NonnullGCPtr<FunctionObject> reject) { m_reject = reject; }
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private:
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PromiseCapability(GCPtr<Object>, GCPtr<FunctionObject>, GCPtr<FunctionObject>);
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virtual void visit_edges(Visitor&) override;
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GCPtr<Object> m_promise;
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GCPtr<FunctionObject> m_resolve;
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GCPtr<FunctionObject> m_reject;
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};
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// 27.2.1.1.1 IfAbruptRejectPromise ( value, capability ), https://tc39.es/ecma262/#sec-ifabruptrejectpromise
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#define __TRY_OR_REJECT(vm, capability, expression, CALL_CHECK) \
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({ \
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auto&& _temporary_try_or_reject_result = (expression); \
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/* 1. If value is an abrupt completion, then */ \
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if (_temporary_try_or_reject_result.is_error()) { \
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/* a. Perform ? Call(capability.[[Reject]], undefined, « value.[[Value]] »). */ \
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CALL_CHECK(JS::call(vm, *(capability)->reject(), js_undefined(), *_temporary_try_or_reject_result.release_error().value())); \
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\
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/* b. Return capability.[[Promise]]. */ \
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return (capability)->promise(); \
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} \
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\
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static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_try_or_reject_result.release_value())>, \
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"Do not return a reference from a fallible expression"); \
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\
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/* 2. Else if value is a Completion Record, set value to value.[[Value]]. */ \
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_temporary_try_or_reject_result.release_value(); \
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})
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#define TRY_OR_REJECT(vm, capability, expression) \
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__TRY_OR_REJECT(vm, capability, expression, TRY)
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#define TRY_OR_MUST_REJECT(vm, capability, expression) \
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__TRY_OR_REJECT(vm, capability, expression, MUST)
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// 27.2.1.1.1 IfAbruptRejectPromise ( value, capability ), https://tc39.es/ecma262/#sec-ifabruptrejectpromise
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#define TRY_OR_REJECT_WITH_VALUE(vm, capability, expression) \
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({ \
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auto&& _temporary_try_or_reject_result = (expression); \
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/* 1. If value is an abrupt completion, then */ \
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if (_temporary_try_or_reject_result.is_error()) { \
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/* a. Perform ? Call(capability.[[Reject]], undefined, « value.[[Value]] »). */ \
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TRY(JS::call(vm, *(capability)->reject(), js_undefined(), *_temporary_try_or_reject_result.release_error().value())); \
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\
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/* b. Return capability.[[Promise]]. */ \
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return Value { (capability)->promise() }; \
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} \
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\
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static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_try_or_reject_result.release_value())>, \
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"Do not return a reference from a fallible expression"); \
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\
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/* 2. Else if value is a Completion Record, set value to value.[[Value]]. */ \
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_temporary_try_or_reject_result.release_value(); \
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})
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// 27.2.1.5 NewPromiseCapability ( C ), https://tc39.es/ecma262/#sec-newpromisecapability
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ThrowCompletionOr<NonnullGCPtr<PromiseCapability>> new_promise_capability(VM& vm, Value constructor);
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}
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