| Issue |
132668
|
| Summary |
Non-constant tuple_size in structured binding is accepted
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
halbi2
|
```
#include <tuple>
struct A {
template<int> friend int get(A);
};
struct Conv {
constexpr operator int() { return 2; }
};
template<> struct std::tuple_size<A> {
static Conv& value; // no definition
};
template<int N> struct std::tuple_element<N, A> {
using type = int;
};
auto [a,b] = A();
```
I think this TU is invalid, because `tuple_size<A>::value` is not an _integral constant expression_.
`clang++ -std=c++20 -c` rejects.
`clang++ -std=c++23 -c` accepts.
Is this intended for [P2280](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2280r4.html)? But other compilers support P2280 too, and they all reject this `tuple_size` code.
I think #132463 could relate.
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