Hi,

the following testcase fails to compile with g++ 4.9.1 and 5.0.0 (20140925).

-- test.cc
template <typename T1, typename S1>
struct B { };

template <typename T1>
struct A
{
    private:
    template <typename T2, typename S2>
        static B<T2, S2> bar();

    public:
    template <typename S2>
        auto foo1() -> decltype(bar<T1, S2>());
};

// (*)
template<>
template<>
auto A<int>::foo1<float>() -> B<int, float>;
-- end of test.cc

$ g++ --version
g++ (GCC) 5.0.0 20140925 (experimental)
$ g++ -c -std=c++11 -c test.cc
test.cc:18:6: error: template-id ‘foo1<float>’ for ‘B<int, float> A<int>::foo1()’ does not match any template declaration
 auto A<int>::foo1<float>() -> B<int, float>;
      ^

but making 'A<T1>::bar' public or using '-fno-access-control' g++ accepts the code OK.

Explicitly using a manually substituted decltype gives a clue of what is going on

-- test.cc
// Declarations of B and A above

// (*)
template<>
template<>
auto A<int>::foo1<float>() -> decltype(A<int>::bar<int, float>());
-- end of test.cc

$ g++ -c -std=c++11 -c test.cc
test.cc:22:6: error: template-id ‘foo1<float>’ for ‘B<int, float> A<int>::foo1()’ does not match any template declaration
 auto A<int>::foo1<float>() -> decltype(A<int>::bar<int, float>());
      ^
test.cc:9:26: error: ‘static B<T2, S2> A<T1>::bar() [with T2 = int; S2 = float; T1 = int]’ is private
         static B<T2, S2> bar();
                          ^
test.cc:22:64: error: within this context
 auto A<int>::foo1<float>() -> decltype(A<int>::bar<int, float>());

Both clang-3.5 and icc 14.0.2 accept this code.

Kind regards,