http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45873
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason at gcc dot gnu.org
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-16
12:01:31 UTC ---
Jason, should deduction succeed here?
template<class, class>
struct pair
{
template<class T1, class U1>
pair(T1&& t, U1&& u) { }
};
template <template <class...> class T, class ...Args>
auto foo(Args... args) -> T<Args...>
{ return T<Args...>(args...); }
int main()
{
// error: no matching function for call to 'foo(int, double)'
foo<pair>(1, 2.0);
}
It looks as though substituting T=pair fails because T's single parameter pack
fails to match pair's two parameters.
If pair is a variadic template with exactly one parameter pack , like p0 below,
then it matches T:
template<class...> struct p0 { };
template<class, class...> struct p1 { };
template<class, class, class...> struct p2 { };
template <template <class...> class T, class ...Args>
auto foo(Args... args) -> T<Args...>
{ return T<Args...>(); }
int main()
{
foo<p0>(1, 2.0); // ok
foo<p1>(1, 2.0); // error
foo<p2>(1, 2.0); // error
}
Is this behaviour correct?
Clang accepts all three calls
