https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86202
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- Actually I forgot we have two copies of the builtin decl. The implicit one gets its type "adjusted" by the duplicate via merge_decls / composite_type (newtype, oldtype) eventually we can simply do composite_type (oldtype, newtype) here ...