[Bug c++/96943] New: incomplete type used in nested name specifier

[tangyixuan at mail dot dlut.edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96943

            Bug ID: 96943
           Summary: incomplete type used in nested name specifier
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tangyixuan at mail dot dlut.edu.cn
  Target Milestone: ---

The following code (maybe valid) is rejected by g++, while is accepted by
clang.

$ cat s.cpp

template < int I > struct CA1{
        enum { EA = 0};
};
template < int I > struct CA2{
        enum {
                EA = 1, EA1 = CA2 <EA> :: EA
        };
};

$ clang++ -c s.cpp
successful.

$ g++ -c s.cpp

s.cpp:6:43: error: incomplete type ‘CA2<1>’ used in nested name specifier
    6 |                 EA = 1, EA1 = CA2 <EA> :: EA
      |    

Is this right?