https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87452
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced a bit more:
struct vector { };
namespace N {
void operator+(const vector&) { }
template<typename T>
auto
f(const T& t)
-> decltype(operator+(t)) // OK
{
return (+t);
}
template<typename T>
auto
g(const T& t)
-> decltype(+t) // fails to find operator defined in N::
{
return (+t);
}
} // namespace N
int main()
{
vector vec;
N::f(vec);
N::g(vec);
}
It works if struct vector and the operator+ overload are in the same namespace,
suggesting the operator can found via ADL, but normal lookup seems to not
consider namespace N.
