| Issue |
101735
|
| Summary |
[Clang] `requires` clause with parameter pack expansion fails equivalence requirements for out of line definitions
|
| Labels |
clang:frontend,
concepts,
diverges-from:gcc
|
| Assignees |
|
| Reporter |
yuxuanchen1997
|
Upstream clang currently rejects the following program:
```
#include <concepts>
#include <utility>
template <typename T>
class A {
template <typename... Ts>
void method(Ts&... ts)
requires requires (T t) {
{ t.method(std::forward<Ts>(ts)...) } -> std::same_as<void>;
};
};
template <typename T>
template <typename... Ts>
void A<T>::method(Ts&... ts)
requires requires (T t) {
{ t.method(std::forward<Ts>(ts)...) } -> std::same_as<void>;
} {}
```
The error message is:
```
test.cc:15:12: error: out-of-line definition of 'method' does not match any declaration in 'A<T>'
15 | void A<T>::method(Ts&... ts)
| ^~~~~~
1 error generated.
```
After getting rid of the `std::forward<Ts>(ts)...`, the error went away.
On an older clang (17-18) this caused a crash with the backtrace. GCC and MSVC accepted this program.
Godbolt: https://godbolt.org/z/YoKM3bzvK
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