https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55004 Bug 55004 depends on bug 66477, which changed state.
Bug 66477 Summary: [constexpr] accepts-invalid with constexpr member call on non-constant reference https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66477 What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution|--- |FIXED