http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47765
--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> 2011-09-08
19:22:58 UTC ---
(In reply to comment #3)
> But another reasonable interpretation would be to skip the parameter
> during deduction and then let normal overload resolution check for the
> conversion; in that case deduction would fail for the first foo and so we
> never
> check the conversion, so we don't try to instantiate A<char>.
But that breaks several libstdc++ tests, and this testcase:
template<typename ItT>
struct A {
typedef typename ItT::value_t value_t;
};
template<typename T>
struct B {
typedef T type_t;
};
template <class T, class... U>
typename A<T>::value_t f(int, T, U...);
template <class T>
T f(T, T);
void foo()
{
B<char> b;
f(b, b);
}
because then we do the substitution before checking whether B<char> can convert
to int. I suppose that we could check conversion between deduction and
substitution...I think I'm going to raise this with the committee.
