[Bug c++/125437] New: ICE when parsing dependent return type E::T inside class template with enum

[s.kimura.h41104 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125437

            Bug ID: 125437
           Summary: ICE when parsing dependent return type E::T inside
                    class template with enum
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: s.kimura.h41104 at gmail dot com
  Target Milestone: ---

Compiler Explorer: https://godbolt.org/z/xWc7ardcW

Reproducer:
```
template <typename T> class C {
  enum class E { e };
  E::T foo() { return E::e; }
};
```

Backtrace:
<source>:3:6: error: 'enum class C<T>::E' is not a class [-Wtemplate-body]
    3 |   E::T foo() { return E::e; }
      |      ^
<source>:3:6: internal compiler error: in constructor_name_p, at
cp/name-lookup.cc:5389
0x29e1d68 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x29d69ab internal_error(char const*, ...)
        ???:0
0xb2fdca fancy_abort(char const*, int, char const*)
        ???:0
0xd831b3 c_parse_file()
        ???:0
0xf122f9 c_common_parse_file()
        ???:0

Clang accepts this code:
https://godbolt.org/z/GWTvGnno7

This ICE goes back to gcc-12:
https://godbolt.org/z/qdMsn7sT1