{"ast_node_type":"other","tokens":[{"end":87,"kind":"keyword","start":0,"text":".unwrap_or_else(||"}]}
                    .unwrap_or_else(|| self.alloc_type_ref_desugared(TypeRef::unit()));
                    .map(|it| self.lower_type_ref(it, impl_trait_lower_fn))
                let mut is_varargs = false;