[Bug c++/77914] Wrong lambda definition accepted

["jason at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77914

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Adam Butcher from comment #4)
> (In reply to Michele Caini from comment #3)
> > (In reply to Jakub Jelinek from comment #1)
> > > Shall we remove that altogether, or just pedwarn on it?
> > 
> > I suspect it should be rejected, unless it is an intended extension of the
> > compiler (for which I've not been able to find the docs - in this case, a
> > pedwarn should be emitted at least).
> 
> It was an intended extension.  Without it, a lambda argument cannot include
> a non-type template parameter or name within its body (without decltype) a
> type inferred from its arguments.  Since it does not conflict with the
> standard, it should be acceptable as a GCC extension.  I didn't document it
> at the time, however, or pedwarn about it.  Possibly at the time it was
> added the standard was still being finalized.
> 
> We could leave this issue open to address the docs and pedwarn unless you
> want to drop the feature completely?

I think we should pedwarn; the committee may well add this syntax in the
future.