https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66834
--- Comment #1 from Jason Merrill <jason at gcc dot gnu.org> --- This was introduced by my patch for bug 66092, applying the tentative resolution of core issue 1430 to concepts as well as alias templates. This makes sense to me since they have the same issue of needing to substitute dependent arguments into the template, in this case during normalization. So I think your example is invalid, but it could use some discussion in core.
