gecko-dev/mfbt/ResultVariant.h
Simon Giesecke ae75c3faa8 Bug 1601556 - Make Result<V, E> a literal type if V and E are literal types and PackingStrategy is not Variant. r=emilio
Also make CompactPair<A, B> a literal type if A and B are literal types,
and add MaybeStorageBase that ought to be used as a basis of MaybeStorage
in a follow-up patch.

Differential Revision: https://phabricator.services.mozilla.com/D55930
2021-03-23 12:35:19 +00:00

54 lines
2.0 KiB
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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* A type suitable for returning either a value or an error from a function. */
#ifndef mozilla_ResultVariant_h
#define mozilla_ResultVariant_h
#include "mozilla/MaybeStorageBase.h"
#include "mozilla/Result.h"
#include "mozilla/Variant.h"
namespace mozilla::detail {
template <typename V, typename E>
class ResultImplementation<V, E, PackingStrategy::Variant> {
mozilla::Variant<V, E> mStorage;
public:
ResultImplementation(ResultImplementation&&) = default;
ResultImplementation(const ResultImplementation&) = delete;
ResultImplementation& operator=(const ResultImplementation&) = delete;
ResultImplementation& operator=(ResultImplementation&&) = default;
explicit ResultImplementation(V&& aValue)
: mStorage(std::forward<V>(aValue)) {}
explicit ResultImplementation(const V& aValue) : mStorage(aValue) {}
template <typename... Args>
explicit ResultImplementation(std::in_place_t, Args&&... aArgs)
: mStorage(VariantType<V>{}, std::forward<Args>(aArgs)...) {}
explicit ResultImplementation(const E& aErrorValue) : mStorage(aErrorValue) {}
explicit ResultImplementation(E&& aErrorValue)
: mStorage(std::forward<E>(aErrorValue)) {}
bool isOk() const { return mStorage.template is<V>(); }
// The callers of these functions will assert isOk() has the proper value, so
// these functions (in all ResultImplementation specializations) don't need
// to do so.
V unwrap() { return std::move(mStorage.template as<V>()); }
const V& inspect() const { return mStorage.template as<V>(); }
E unwrapErr() { return std::move(mStorage.template as<E>()); }
const E& inspectErr() const { return mStorage.template as<E>(); }
};
} // namespace mozilla::detail
#endif // mozilla_ResultVariant_h