https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55004 Bug 55004 depends on bug 64977, which changed state.
Bug 64977 Summary: constexpr variable initialization by reference in lambda rejected https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64977 What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |INVALID