https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71679
--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
The testcase can be further reduced:
template <int> struct A;
struct B {
template <int, int> friend struct ::A;
};
When using A instead of ::A it works fine and gcc errors out:
llvm.ii:3:37: error: redeclared with 2 template parameters
template <int, int> friend struct A;
^
llvm.ii:1:23: note: previous declaration ‘template<int <anonymous> > struct A’
used 1 template parameter
template <int> struct A;
^
