//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17
// <variant>
// template <class R, class Visitor, class... Variants>
// constexpr R visit(Visitor&& vis, Variants&&... vars);
#include <cassert>
#include <memory>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>
#include <variant>
#include "test_macros.h"
#include "variant_test_helpers.h"
template <typename ReturnType>
void test_call_operator_forwarding() {
using Fn = ForwardingCallObject;
Fn obj{};
const Fn &cobj = obj;
{ // test call operator forwarding - no variant
std::visit<ReturnType>(obj);
assert(Fn::check_call<>(CT_NonConst | CT_LValue));
std::visit<ReturnType>(cobj);
assert(Fn::check_call<>(CT_Const | CT_LValue));
std::visit<ReturnType>(std::move(obj));
assert(Fn::check_call<>(CT_NonConst | CT_RValue));
std::visit<ReturnType>(std::move(cobj));
assert(Fn::check_call<>(CT_Const | CT_RValue));
}
{ // test call operator forwarding - single variant, single arg
using V = std::variant<int>;
V v(42);
std::visit<ReturnType>(obj, v);
assert(Fn::check_call<int &>(CT_NonConst | CT_LValue));
std::visit<ReturnType>(cobj, v);
assert(Fn::check_call<int &>(CT_Const | CT_LValue));
std::visit<ReturnType>(std::move(obj), v);
assert(Fn::check_call<int &>(CT_NonConst | CT_RValue));
std::visit<ReturnType>(std::move(cobj), v);
assert(Fn::check_call<int &>(CT_Const | CT_RValue));
}
{ // test call operator forwarding - single variant, multi arg
using V = std::variant<int, long, double>;
V v(42l);
std::visit<ReturnType>(obj, v);
assert(Fn::check_call<long &>(CT_NonConst | CT_LValue));
std::visit<ReturnType>(cobj, v);
assert(Fn::check_call<long &>(CT_Const | CT_LValue));
std::visit<ReturnType>(std::move(obj), v);
assert(Fn::check_call<long &>(CT_NonConst | CT_RValue));
std::visit<ReturnType>(std::move(cobj), v);
assert(Fn::check_call<long &>(CT_Const | CT_RValue));
}
{ // test call operator forwarding - multi variant, multi arg
using V = std::variant<int, long, double>;
using V2 = std::variant<int *, std::string>;
V v(42l);
V2 v2("hello");
std::visit<int>(obj, v, v2);
assert((Fn::check_call<long &, std::string &>(CT_NonConst | CT_LValue)));
std::visit<ReturnType>(cobj, v, v2);
assert((Fn::check_call<long &, std::string &>(CT_Const | CT_LValue)));
std::visit<ReturnType>(std::move(obj), v, v2);
assert((Fn::check_call<long &, std::string &>(CT_NonConst | CT_RValue)));
std::visit<ReturnType>(std::move(cobj), v, v2);
assert((Fn::check_call<long &, std::string &>(CT_Const | CT_RValue)));
}
{
using V = std::variant<int, long, double, std::string>;
V v1(42l), v2("hello"), v3(101), v4(1.1);
std::visit<ReturnType>(obj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int &, double &>(CT_NonConst | CT_LValue)));
std::visit<ReturnType>(cobj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int &, double &>(CT_Const | CT_LValue)));
std::visit<ReturnType>(std::move(obj), v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int &, double &>(CT_NonConst | CT_RValue)));
std::visit<ReturnType>(std::move(cobj), v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int &, double &>(CT_Const | CT_RValue)));
}
{
using V = std::variant<int, long, double, int*, std::string>;
V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
std::visit<ReturnType>(obj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_NonConst | CT_LValue)));
std::visit<ReturnType>(cobj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_Const | CT_LValue)));
std::visit<ReturnType>(std::move(obj), v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_NonConst | CT_RValue)));
std::visit<ReturnType>(std::move(cobj), v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int *&, double &>(CT_Const | CT_RValue)));
}
}
template <typename ReturnType>
void test_argument_forwarding() {
using Fn = ForwardingCallObject;
Fn obj{};
const auto Val = CT_LValue | CT_NonConst;
{ // single argument - value type
using V = std::variant<int>;
V v(42);
const V &cv = v;
std::visit<ReturnType>(obj, v);
assert(Fn::check_call<int &>(Val));
std::visit<ReturnType>(obj, cv);
assert(Fn::check_call<const int &>(Val));
std::visit<ReturnType>(obj, std::move(v));
assert(Fn::check_call<int &&>(Val));
std::visit<ReturnType>(obj, std::move(cv));
assert(Fn::check_call<const int &&>(Val));
}
{ // multi argument - multi variant
using V = std::variant<int, std::string, long>;
V v1(42), v2("hello"), v3(43l);
std::visit<ReturnType>(obj, v1, v2, v3);
assert((Fn::check_call<int &, std::string &, long &>(Val)));
std::visit<ReturnType>(obj, std::as_const(v1), std::as_const(v2), std::move(v3));
assert((Fn::check_call<const int &, const std::string &, long &&>(Val)));
}
{
using V = std::variant<int, long, double, std::string>;
V v1(42l), v2("hello"), v3(101), v4(1.1);
std::visit<ReturnType>(obj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int &, double &>(Val)));
std::visit<ReturnType>(obj, std::as_const(v1), std::as_const(v2), std::move(v3), std::move(v4));
assert((Fn::check_call<const long &, const std::string &, int &&, double &&>(Val)));
}
{
using V = std::variant<int, long, double, int*, std::string>;
V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
std::visit<ReturnType>(obj, v1, v2, v3, v4);
assert((Fn::check_call<long &, std::string &, int *&, double &>(Val)));
std::visit<ReturnType>(obj, std::as_const(v1), std::as_const(v2), std::move(v3), std::move(v4));
assert((Fn::check_call<const long &, const std::string &, int *&&, double &&>(Val)));
}
}
template <typename ReturnType>
void test_return_type() {
using Fn = ForwardingCallObject;
Fn obj{};
const Fn &cobj = obj;
{ // test call operator forwarding - no variant
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj))), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj))), ReturnType>);
}
{ // test call operator forwarding - single variant, single arg
using V = std::variant<int>;
V v(42);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj, v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj, v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj), v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj), v)), ReturnType>);
}
{ // test call operator forwarding - single variant, multi arg
using V = std::variant<int, long, double>;
V v(42l);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj, v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj, v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj), v)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj), v)), ReturnType>);
}
{ // test call operator forwarding - multi variant, multi arg
using V = std::variant<int, long, double>;
using V2 = std::variant<int *, std::string>;
V v(42l);
V2 v2("hello");
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj, v, v2)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj, v, v2)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj), v, v2)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj), v, v2)), ReturnType>);
}
{
using V = std::variant<int, long, double, std::string>;
V v1(42l), v2("hello"), v3(101), v4(1.1);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj, v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj, v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj), v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj), v1, v2, v3, v4)), ReturnType>);
}
{
using V = std::variant<int, long, double, int*, std::string>;
V v1(42l), v2("hello"), v3(nullptr), v4(1.1);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(obj, v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(cobj, v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(obj), v1, v2, v3, v4)), ReturnType>);
static_assert(std::is_same_v<decltype(std::visit<ReturnType>(std::move(cobj), v1, v2, v3, v4)), ReturnType>);
}
}
void test_constexpr_void() {
constexpr ReturnFirst obj{};
constexpr ReturnArity aobj{};
{
using V = std::variant<int>;
constexpr V v(42);
static_assert((std::visit<void>(obj, v), 42) == 42, "");
}
{
using V = std::variant<short, long, char>;
constexpr V v(42l);
static_assert((std::visit<void>(obj, v), 42) == 42, "");
}
{
using V1 = std::variant<int>;
using V2 = std::variant<int, char *, long long>;
using V3 = std::variant<bool, int, int>;
constexpr V1 v1;
constexpr V2 v2(nullptr);
constexpr V3 v3;
static_assert((std::visit<void>(aobj, v1, v2, v3), 3) == 3, "");
}
{
using V1 = std::variant<int>;
using V2 = std::variant<int, char *, long long>;
using V3 = std::variant<void *, int, int>;
constexpr V1 v1;
constexpr V2 v2(nullptr);
constexpr V3 v3;
static_assert((std::visit<void>(aobj, v1, v2, v3), 3) == 3, "");
}
{
using V = std::variant<int, long, double, int *>;
constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
static_assert((std::visit<void>(aobj, v1, v2, v3, v4), 4) == 4, "");
}
{
using V = std::variant<int, long, double, long long, int *>;
constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
static_assert((std::visit<void>(aobj, v1, v2, v3, v4), 4) == 4, "");
}
}
void test_constexpr_int() {
constexpr ReturnFirst obj{};
constexpr ReturnArity aobj{};
{
using V = std::variant<int>;
constexpr V v(42);
static_assert(std::visit<int>(obj, v) == 42, "");
}
{
using V = std::variant<short, long, char>;
constexpr V v(42l);
static_assert(std::visit<int>(obj, v) == 42, "");
}
{
using V1 = std::variant<int>;
using V2 = std::variant<int, char *, long long>;
using V3 = std::variant<bool, int, int>;
constexpr V1 v1;
constexpr V2 v2(nullptr);
constexpr V3 v3;
static_assert(std::visit<int>(aobj, v1, v2, v3) == 3, "");
}
{
using V1 = std::variant<int>;
using V2 = std::variant<int, char *, long long>;
using V3 = std::variant<void *, int, int>;
constexpr V1 v1;
constexpr V2 v2(nullptr);
constexpr V3 v3;
static_assert(std::visit<int>(aobj, v1, v2, v3) == 3, "");
}
{
using V = std::variant<int, long, double, int *>;
constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
static_assert(std::visit<int>(aobj, v1, v2, v3, v4) == 4, "");
}
{
using V = std::variant<int, long, double, long long, int *>;
constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
static_assert(std::visit<int>(aobj, v1, v2, v3, v4) == 4, "");
}
}
template <typename ReturnType>
void test_exceptions() {
#ifndef TEST_HAS_NO_EXCEPTIONS
ReturnArity obj{};
auto test = [&](auto &&... args) {
try {
std::visit<ReturnType>(obj, args...);
} catch (const std::bad_variant_access &) {
return true;
} catch (...) {
}
return false;
};
{
using V = std::variant<int, MakeEmptyT>;
V v;
makeEmpty(v);
assert(test(v));
}
{
using V = std::variant<int, MakeEmptyT>;
using V2 = std::variant<long, std::string, void *>;
V v;
makeEmpty(v);
V2 v2("hello");
assert(test(v, v2));
}
{
using V = std::variant<int, MakeEmptyT>;
using V2 = std::variant<long, std::string, void *>;
V v;
makeEmpty(v);
V2 v2("hello");
assert(test(v2, v));
}
{
using V = std::variant<int, MakeEmptyT>;
using V2 = std::variant<long, std::string, void *, MakeEmptyT>;
V v;
makeEmpty(v);
V2 v2;
makeEmpty(v2);
assert(test(v, v2));
}
{
using V = std::variant<int, long, double, MakeEmptyT>;
V v1(42l), v2(101), v3(202), v4(1.1);
makeEmpty(v1);
assert(test(v1, v2, v3, v4));
}
{
using V = std::variant<int, long, double, long long, MakeEmptyT>;
V v1(42l), v2(101), v3(202), v4(1.1);
makeEmpty(v1);
makeEmpty(v2);
makeEmpty(v3);
makeEmpty(v4);
assert(test(v1, v2, v3, v4));
}
#endif
}
// See https://bugs.llvm.org/show_bug.cgi?id=31916
template <typename ReturnType>
void test_caller_accepts_nonconst() {
struct A {};
struct Visitor {
auto operator()(A&) {
if constexpr (!std::is_void_v<ReturnType>)
{
return ReturnType{};
}
}
};
std::variant<A> v;
std::visit<ReturnType>(Visitor{}, v);
}
void test_constexpr_explicit_side_effect() {
auto test_lambda = [](int arg) constexpr {
std::variant<int> v = 101;
std::visit<void>([arg](int& x) constexpr { x = arg; }, v);
return std::get<int>(v);
};
static_assert(test_lambda(202) == 202, "");
}
void test_derived_from_variant() {
struct MyVariant : std::variant<short, long, float> {};
std::visit<bool>(
[](auto x) {
assert(x == 42);
return true;
},
MyVariant{42});
std::visit<bool>(
[](auto x) {
assert(x == -1.3f);
return true;
},
MyVariant{-1.3f});
// Check that visit does not take index nor valueless_by_exception members from the base class.
struct EvilVariantBase {
int index;
char valueless_by_exception;
};
struct EvilVariant1 : std::variant<int, long, double>,
std::tuple<int>,
EvilVariantBase {
using std::variant<int, long, double>::variant;
};
std::visit<bool>(
[](auto x) {
assert(x == 12);
return true;
},
EvilVariant1{12});
std::visit<bool>(
[](auto x) {
assert(x == 12.3);
return true;
},
EvilVariant1{12.3});
// Check that visit unambiguously picks the variant, even if the other base has __impl member.
struct ImplVariantBase {
struct Callable {
bool operator()() const { assert(false); return false; }
};
Callable __impl;
};
struct EvilVariant2 : std::variant<int, long, double>, ImplVariantBase {
using std::variant<int, long, double>::variant;
};
std::visit<bool>(
[](auto x) {
assert(x == 12);
return true;
},
EvilVariant2{12});
std::visit<bool>(
[](auto x) {
assert(x == 12.3);
return true;
},
EvilVariant2{12.3});
}
struct any_visitor {
template <typename T>
bool operator()(const T&) {
return true;
}
};
template <typename T, typename = decltype(std::visit<bool>(
std::declval<any_visitor&>(), std::declval<T>()))>
constexpr bool has_visit(int) {
return true;
}
template <typename T>
constexpr bool has_visit(...) {
return false;
}
void test_sfinae() {
struct BadVariant : std::variant<short>, std::variant<long, float> {};
static_assert(has_visit<std::variant<int> >(int()));
static_assert(!has_visit<BadVariant>(int()));
}
int main(int, char**) {
test_call_operator_forwarding<void>();
test_argument_forwarding<void>();
test_return_type<void>();
test_constexpr_void();
test_exceptions<void>();
test_caller_accepts_nonconst<void>();
test_call_operator_forwarding<int>();
test_argument_forwarding<int>();
test_return_type<int>();
test_constexpr_int();
test_exceptions<int>();
test_caller_accepts_nonconst<int>();
test_constexpr_explicit_side_effect();
test_derived_from_variant();
test_sfinae();
return 0;
}
Codebase Browser
llvm