https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106110
--- Comment #1 from Ted Lyngmo <ted at lyncon dot se> ---
Sorry, the helper variable template should be:
```
template <class... Args>
static constexpr bool is_foo_call_ambiguous_v =
is_foo_call_ambiguous<Args...>::value;
```
It gives the same result: https://godbolt.org/z/bKbn8Gre7
