fn lookup_impl_assoc_item_for_trait_ref<'db>( infcx: &InferCtxt<'db>, trait_ref: TraitRef<'db>, env: ParamEnv<'db>, name: &Name, ) -> Option<(Either<AssocItemId, (BuiltinDeriveImplId, BuiltinDeriveImplMethod)>, GenericArgs<'db>)>