https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97034
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Alternative patch that I'm more happy about: --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -28761,6 +28761,7 @@ build_deduction_guide (tree type, tree ctor, tree outer_args, tsubst_flags_t com tree ded_fn = build_lang_decl_loc (loc, FUNCTION_DECL, dguide_name (type), fntype); + DECL_CONTEXT (ded_fn) = type; DECL_ARGUMENTS (ded_fn) = fargs; DECL_ARTIFICIAL (ded_fn) = true; DECL_NONCONVERTING_P (ded_fn) = explicit_p;