[Bug c++/125537] [contracts] g++-16 crashes on contracts pre and post with placeholder return type

[waffl3x at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125537

--- Comment #5 from Waffl3x <waffl3x at gcc dot gnu.org> ---
```
bool g(int) { return true; }

template<typename T>
auto f(T a)
  pre(g(a)) {}

template auto f<int>(int);
```
Reproducer without member functions.