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/*
* Copyright 2024 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <android-base/expected.h>
#include <ftl/optional.h>
#include <utility>
namespace android::ftl {
// Superset of base::expected<T, E> with monadic operations.
//
// TODO: Extend std::expected<T, E> in C++23.
//
template <typename T, typename E>
struct Expected final : base::expected<T, E> {
using Base = base::expected<T, E>;
using Base::expected;
using Base::error;
using Base::has_value;
using Base::value;
template <typename P>
constexpr bool has_error(P predicate) const {
return !has_value() && predicate(error());
}
constexpr Optional<T> value_opt() const& {
return has_value() ? Optional(value()) : std::nullopt;
}
constexpr Optional<T> value_opt() && {
return has_value() ? Optional(std::move(value())) : std::nullopt;
}
// Delete new for this class. Its base doesn't have a virtual destructor, and
// if it got deleted via base class pointer, it would cause undefined
// behavior. There's not a good reason to allocate this object on the heap
// anyway.
static void* operator new(size_t) = delete;
static void* operator new[](size_t) = delete;
};
template <typename E>
constexpr auto Unexpected(E&& error) {
return base::unexpected(std::forward<E>(error));
}
} // namespace android::ftl
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