1// Copyright 2018 The Abseil Authors.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14//
15// -----------------------------------------------------------------------------
16// bad_variant_access.h
17// -----------------------------------------------------------------------------
18//
19// This header file defines the `absl::bad_variant_access` type.
20
21#ifndef ABSL_TYPES_BAD_VARIANT_ACCESS_H_
22#define ABSL_TYPES_BAD_VARIANT_ACCESS_H_
23
24#include <stdexcept>
25
26#include "absl/base/config.h"
27
28#ifdef ABSL_HAVE_STD_VARIANT
29
30#include <variant>
31
32namespace absl {
33using std::bad_variant_access;
34} // namespace absl
35
36#else // ABSL_HAVE_STD_VARIANT
37
38namespace absl {
39
40// -----------------------------------------------------------------------------
41// bad_variant_access
42// -----------------------------------------------------------------------------
43//
44// An `absl::bad_variant_access` type is an exception type that is thrown in
45// the following cases:
46//
47// * Calling `absl::get(absl::variant) with an index or type that does not
48// match the currently selected alternative type
49// * Calling `absl::visit on an `absl::variant` that is in the
50// `variant::valueless_by_exception` state.
51//
52// Example:
53//
54// absl::variant<int, std::string> v;
55// v = 1;
56// try {
57// absl::get<std::string>(v);
58// } catch(const absl::bad_variant_access& e) {
59// std::cout << "Bad variant access: " << e.what() << '\n';
60// }
61class bad_variant_access : public std::exception {
62 public:
63 bad_variant_access() noexcept = default;
64 ~bad_variant_access() override;
65 const char* what() const noexcept override;
66};
67
68namespace variant_internal {
69
70[[noreturn]] void ThrowBadVariantAccess();
71[[noreturn]] void Rethrow();
72
73} // namespace variant_internal
74} // namespace absl
75
76#endif // ABSL_HAVE_STD_VARIANT
77
78#endif // ABSL_TYPES_BAD_VARIANT_ACCESS_H_
79