[Bug c++/79652] [5/6/7 Regression] ICE on invalid c++ code in warn_extern_redeclared_static in cp/decl.c:1231

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79652

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Reduced:

namespace {
  struct S {
    int n;
  } T;
  using T = decltype(S :: n);
  namespace {
    extern int x;
    extern int x;
  }
}