https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107461
--- Comment #9 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #7)
> Reduced testcase:
Interestingly Clang also rejects this testcase, so I'm not sure if we were
correct to accept it previously.
Here's a more reduced testcase that seems clearly valid:
template <typename T> T foo ();
template <typename> struct A { };
template <typename T> struct B {
template <typename U, typename = A<decltype (foo<T>() (U()))>>
static void bar(U);
};
int main() {
B<int> b;
B<void(*)(int)>::bar(0);
}
<stdin>: In function ‘int main()’:
<stdin>:12:23: error: no matching function for call to ‘B<void
(*)(int)>::bar(int)’
<stdin>:7:15: note: candidate: ‘template<class U, class> static void
B<T>::bar(U) [with <template-parameter-2-2> = U; T = void (*)(int)]’
<stdin>:7:15: note: template argument deduction/substitution failed:
<stdin>:6:54: error: expression cannot be used as a function
If we remove the line #1 then this bogus error disappears.
