https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67491 Bug 67491 depends on bug 92771, which changed state.
Bug 92771 Summary: [9/10 Regression] Concept won't use default template argument https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92771 What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |DUPLICATE