{"ast_node_type":"other","tokens":[{"end":86,"kind":"keyword","start":0,"text":"ty::Coroutine(def,"}]}
                ty::Coroutine(def, ..) if self.infcx.tcx.coroutine_is_async(*def) => {
            ty_err: match output_ty.kind() {
                    FnMutReturnTypeErr::ReturnAsyncBlock { span: *span }