[Bug c++/63378] New: decltype and access control issues

["roger.ferrer at bsc dot es" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63378

            Bug ID: 63378
           Summary: decltype and access control issues
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: roger.ferrer at bsc dot es

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 âfoo1<float>â for âB<int, float>
A<int>::foo1()â 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 âfoo1<float>â for âB<int, float>
A<int>::foo1()â does not match any template declaration
 auto A<int>::foo1<float>() -> decltype(A<int>::bar<int, float>());
      ^
test.cc:9:26: error: âstatic B<T2, S2> A<T1>::bar() [with T2 = int; S2 = float;
T1 = int]â 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,