[Bug c/81543] attribute may_alias on function and variable declarations silently accepted

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81543

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
But adding one wouldn't help because

487       /* If we require a type, but were passed a decl, set up to make a
488          new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
489          would have applied if we'd been passed a type, but we cannot
modify
490          the decl's type in place here.  */
491       if (spec->type_required && DECL_P (*anode))
492         {
493           anode = &TREE_TYPE (*anode);
494           flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
495         }