[Bug c++/84689] is_invocable is true even for call operator via ambiguous base

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84689

TC <rs2740 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rs2740 at gmail dot com

--- Comment #1 from TC <rs2740 at gmail dot com> ---
With library dependency removed:

struct base {
    void operator()(int ) { }
};

struct a : base { };
struct b : base { };

struct f: a, b {
    using a::operator();
    using b::operator();
};

template<class T> auto g(int) -> decltype(T()(0), 0);
template<class T> auto g(...) -> long;

template<class, class> struct Same;
template<class T> struct Same<T, T> {};

Same<decltype(g<f>(0)), long> s;

Accepted by clang, rejected by gcc, who thinks that decltype(g<f>(0)) is int.