src/core/lib/gprpp/match.h

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// Copyright 2021 gRPC authors.
//
// 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.
 
#ifndef GRPC_CORE_LIB_GPRPP_MATCH_H
#define GRPC_CORE_LIB_GPRPP_MATCH_H
 
#include <grpc/support/port_platform.h>
 
#include <type_traits>
 
#include "absl/types/variant.h"
 
#include "src/core/lib/gprpp/overload.h"
 
namespace grpc_core {
 
namespace detail {
 
template <typename... Cases>
struct MatchPointerExtractor {
  OverloadType<Cases...> cases;
  template <typename T>
  auto operator()(T& value) -> decltype(cases(&value)) {
    return cases(&value);
  }
};
 
}  // namespace detail
 
template <typename... Fs, typename T0, typename... Ts>
auto Match(const absl::variant<T0, Ts...>& value, Fs... fs)
    -> decltype(std::declval<OverloadType<Fs...>>()(std::declval<T0>())) {
  return absl::visit(Overload(std::move(fs)...), value);
}
 
template <typename... Fs, typename T0, typename... Ts>
auto MatchMutable(absl::variant<T0, Ts...>* value, Fs... fs)
    -> decltype(std::declval<OverloadType<Fs...>>()(std::declval<T0*>())) {
  return absl::visit(detail::MatchPointerExtractor<Fs...>{OverloadType<Fs...>(
                         std::move(fs)...)},
                     *value);
}
 
}  // namespace grpc_core
 
#endif  // GRPC_CORE_LIB_GPRPP_MATCH_H