| Issue |
63845
|
| Summary |
Wrong evaluation of a `if constexpr requires`
|
| Labels |
|
| Assignees |
|
| Reporter |
Fedr
|
The following program
```
#include <array>
#include <vector>
template <typename T>
constexpr std::size_t get_length(const T &t) {
return t.size();
}
template <typename T, std::size_t N>
constexpr auto get_length(const std::array<T, N> &) {
return std::integral_constant<std::size_t, N>();
}
static_assert( get_length(std::array<int, 3>())() == 3 );
static_assert( requires { typename std::array<int, get_length(std::array<int, 3>())>; } );
auto foo(auto length) {
// If length could be evaluated at compile time,
if constexpr (requires { typename std::array<int, length>; })
return std::array<int, length>{};
// Otherwise,
else
return std::vector<int>(length);
}
int main() {
auto x = foo(get_length(std::vector<int>(5)));
x.resize(1); // array does not have resize
auto y = foo(get_length(std::array<int, 3>()));
static_assert( y.size() == 3 ); // in Clang y is vector?
}
```
is accepted by GCC and MSVC. But in Clang `y` is a `std::vector` for some reason. Online demo: https://gcc.godbolt.org/z/h53zc3bjv
Related discussion: https://stackoverflow.com/a/76673819/7325599
Could you please check?
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