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Fix return type of std::tuple_cat.

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When the arguments to tuple cat were const, the const was incorrectly
propagated into the type of the resulting tuple. For example:

const std::tuple<int> t(42);
auto r = std::tuple_cat(t, t);
// Incorrect! should be std::tuple<int, int>.
static_assert(is_same_v<decltype(r), std::tuple<const int, const int>>);

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@359255 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2019-04-26 01:02:18 +00:00
parent ddc44427f8
commit cc57a78190
2 changed files with 17 additions and 2 deletions
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4
include/tuple
View File

@@ -1211,7 +1211,7 @@ template <class ..._Types, class _Tuple0>
struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0>
{
typedef typename __tuple_cat_type<tuple<_Types...>,
typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type>::type
typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type>::type
type;
};
@@ -1220,7 +1220,7 @@ struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...
: public __tuple_cat_return_1<
typename __tuple_cat_type<
tuple<_Types...>,
typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type
typename __make_tuple_types<typename __uncvref<_Tuple0>::type>::type
>::type,
__tuple_like<typename remove_reference<_Tuple1>::type>::value,
_Tuple1, _Tuples...>

15
test/std/utilities/tuple/tuple.tuple/tuple.creation/tuple_cat.pass.cpp
View File

@@ -238,6 +238,21 @@ int main(int, char**)
);
assert(t2 == std::make_tuple(std::make_tuple(1), std::make_tuple(2)));
}
{
int x = 101;
std::tuple<int, int&, const int&, int&&> t(42, x, x, std::move(x));
const auto& ct = t;
std::tuple<int, int&, const int&> t2(42, x, x);
const auto& ct2 = t2;
auto r = std::tuple_cat(std::move(t), std::move(ct), t2, ct2);
ASSERT_SAME_TYPE(decltype(r), std::tuple<
int, int&, const int&, int&&,
int, int&, const int&, int&&,
int, int&, const int&,
int, int&, const int&>);
((void)r);
}
return 0;
}