{"ast_node_type":"variable","tokens":[{"end":71,"kind":"keyword","start":0,"text":"let"}]}
            let annotation = self.instantiate_canonical(span, user_ty);
            let CanonicalUserTypeAnnotation { span, ref user_ty, inferred_ty } = *user_annotation;
            if let ty::UserTypeKind::TypeOf(def, args) = annotation.kind