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68 lines
2.0 KiB
68 lines
2.0 KiB
/*
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* Copyright 2014 Google Inc. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FRUIT_META_ERRORS_H
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#define FRUIT_META_ERRORS_H
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#include <fruit/impl/meta/basics.h>
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#include <fruit/impl/meta/logical_operations.h>
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namespace fruit {
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namespace impl {
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namespace meta {
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template <typename T>
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struct CheckIfError {
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using type = T;
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};
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template <typename ErrorTag, typename... ErrorArgs>
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struct CheckIfError<Error<ErrorTag, ErrorArgs...>> {
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using type = typename ErrorTag::template apply<ErrorArgs...>;
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};
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// ConstructError(ErrorTag, Args...) returns Error<ErrorTag, Args...>.
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// Never construct an Error<...> directly, using this metafunction makes debugging easier.
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struct ConstructError {
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template <typename ErrorTag, typename... Args>
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struct apply {
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#if FRUIT_DEEP_TEMPLATE_INSTANTIATION_STACKTRACES_FOR_ERRORS
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static_assert(true || sizeof(typename CheckIfError<Error<ErrorTag, UnwrapType<Args>...>>::type), "");
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#endif
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using type = Error<ErrorTag, typename TypeUnwrapper<Args>::type...>;
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};
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};
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// Extracts the first error in the given types.
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struct ExtractFirstError {
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template <typename... Types>
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struct apply;
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template <typename Type, typename... Types>
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struct apply<Type, Types...> : public apply<Types...> {};
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template <typename ErrorTag, typename... ErrorParams, typename... Types>
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struct apply<Error<ErrorTag, ErrorParams...>, Types...> {
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using type = Error<ErrorTag, ErrorParams...>;
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};
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};
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} // namespace meta
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} // namespace impl
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} // namespace fruit
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#endif // FRUIT_META_ERRORS_H
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