[Bug c++/58590] New: [C++11] Hidden typename not ill-formed under SFINAE conditions

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58590

            Bug ID: 58590
           Summary: [C++11] Hidden typename not ill-formed under SFINAE
                    conditions
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: daniel.kruegler at googlemail dot com

gcc 4.9.0 20130922 (experimental) compiled with the flags

-std=c++11 -Wall -pedantic-errors

rejects the following code:

//---------------------
struct S { int member; struct member{}; };

template<class T, class = typename T::member>
auto f(int) -> char(&)[1];

template<class T>
auto f(...) -> char(&)[2];

static_assert(sizeof(f<S>(0)) == 2, "");

int main() {
}
//---------------------

"main.cpp|9|error: static assertion failed: |"

After discussion with Richard Smith:

The presence of 'typename' before 'T::member' does not influence name lookup,
and 'S::member' as a template-argument names the non-static data member, not
the type, by [basic.scope.hiding]p2. The relevant rule in [temp.res]p4.

It seems that GCC uses the elaborated-type-specifier lookup instead here.