[Bug c++/58878] New: Template parameter name can be hidden in a template member function defined inside the class specifier

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58878

            Bug ID: 58878
           Summary: Template parameter name can be hidden in a template
                    member function defined inside the class specifier
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: roger.ferrer at bsc dot es

Hi,

g++ allows declarations to hide a template-parameter name in template member
functions defined inside the class-specifier.

I have not been able to find whether this was expected behaviour in g++ so
I'm inclined to believe this is an error in g++.

Following is a testcase where several declarations attempt to hide
template-parameter names 't' and 's' in the scope.

g++ accepts cases 1, 5 and 6 and (I think) it should not allow them. The
remaining cases seem to be correctly diagnosed.

This fails both in g++ 4.8.1 and g++ 4.9.0 20131015 (experimental).

-- test.c
// Template-members of non-template class
struct A
{
    template <typename t>
        void f()
        {
            int t = 1; // Error. g++ does NOT complain
        }

    template <typename t>
        void g();
};

template <typename t>
void A::g()
{
    int t = 2; // OK. g++ DOES complain
}

// (Non-template) Members of template class
template <typename t>
struct B
{
    void f()
    {
        int t = 3; // OK. g++ DOES complain
    }

    void g();
};

template <typename t>
void B<t>::g()
{
    int t = 4; // OK. g++ DOES complain
}


// Template members of template class
template <typename t>
struct C
{
    template <typename s>
    void f()
    {
        int t = 5; // Error. g++ does NOT complain
        int s = 6; // Error. g++ does NOT complain
    }

    template <typename s>
    void g();
};

template <typename t>
template <typename s>
void C<t>::g()
{
    int t = 7; // OK. g++ DOES complain
    int s = 8; // OK. g++ DOES complain
}
-- end of test.cc

$ g++ -c test.cc
test.cc: In member function âvoid A::g()â:
test.cc:17:9: error: declaration of âint tâ
     int t = 2; // OK. g++ DOES complain
         ^
test.cc:14:11: error:  shadows template parm âclass tâ
 template <typename t>
           ^
test.cc: In member function âvoid B<t>::f()â:
test.cc:26:13: error: declaration of âint tâ
         int t = 3; // OK. g++ DOES complain
             ^
test.cc:21:11: error:  shadows template parm âclass tâ
 template <typename t>
           ^
test.cc: In member function âvoid B<t>::g()â:
test.cc:35:9: error: declaration of âint tâ
     int t = 4; // OK. g++ DOES complain
         ^
test.cc:32:11: error:  shadows template parm âclass tâ
 template <typename t>
           ^
test.cc: In member function âvoid C<t>::g()â:
test.cc:58:9: error: declaration of âint tâ
     int t = 7; // OK. g++ DOES complain
         ^
test.cc:54:11: error:  shadows template parm âclass tâ
 template <typename t>
           ^
test.cc:59:9: error: declaration of âint sâ
     int s = 8; // OK. g++ DOES complain
         ^
test.cc:55:11: error:  shadows template parm âclass sâ
 template <typename s>

I'd expect error messages for 1, 5 and 6 to appear as well.

Kind regards,