syntax_data: {"ast_node_type":"variable","tokens":[{"end":64,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let args = self.fold_closure_args(def_id, args);
context_before:             ty::CoroutineWitness(def_id, args) => {
context_after:                 Ty::new_coroutine_witness(self.tcx, def_id, args)