{"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"FnMutReturnTypeErr::ReturnAsyncBlock"}]}
                    FnMutReturnTypeErr::ReturnAsyncBlock { span: *span }
                ty::Coroutine(def, ..) if self.infcx.tcx.coroutine_is_async(*def) => {
                }