[Bug c++/120917] warning: use of 'auto' in template argument only available with '-fconcepts-ts'

[f.heckenbach--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120917

--- Comment #16 from Frank Heckenbach <f.heckenb...@fh-soft.de> ---
(In reply to Jason Merrill from comment #15)
> I suppose we could downgrade the error to a permerror (to make it compile
> with -fpermissive), since the above transformation still works apart from
> the error.  Would that be useful to you?

Ideally, it'd be a separate option. I'd like to avoid "-fpermissive" as it
allows more nonconformant features and paves the way for the next problem of
this kind in the future.