https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97890
David Binderman <dcb314 at hotmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jason at gcc dot gnu.org --- Comment #4 from David Binderman <dcb314 at hotmail dot com> --- A quick review of the git log suggests Jason Merrill 's commit hashed as baf38d2e363971ed8baa5f82b2eaf21cd8e74aae is a hot candidate. Given that clang-11 won't compile the code (even with -std=c++20) and gcc didn't used to, is it perhaps a good idea to a) go back to old behaviour by default for gcc. b) put gcc's new behaviour into -std=c++20 only. Perhaps Jason is well placed to advise further.