[Bug c++/94529] New: Wrong error message for template member function specialization

["kunal.tyagi.3.1994 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94529

            Bug ID: 94529
           Summary: Wrong error message for template member function
                    specialization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kunal.tyagi.3.1994 at gmail dot com
  Target Milestone: ---

[Relevant godbolt](https://godbolt.org/z/trqEMV)

Snippet:
```
template <class T>
struct foo {
    // the issue is const here
    void bar(T& foobar) const { foobar = 0; }
};

template <> void
foo<int>::bar(int& foobar) { foobar = 9; }
```

GCC (trunk) gives the error message:
```
<source>:8:1: error: template-id 'bar<>' for 'void foo<int>::bar(int&)' does
not match any template declaration

    8 | foo<int>::bar(int& foobar) { foobar = 9; }

      | ^~~~~~~~

<source>:8:1: note: saw 1 'template<>', need 2 for specializing a member
function template
```

A better error message is reported by clang (3.5 onwards):
```
<source>:8:11: error: out-of-line definition of 'bar' does not match any
declaration in 'foo<int>'

foo<int>::bar(int& foobar) { foobar = 9; }

          ^~~

<source>:4:10: note: member declaration does not match because it is const
qualified

    void bar(T& foobar) const { foobar = 0; }

         ^                                  ~
```