syntax_data: {"ast_node_type":"variable","tokens":[{"end":77,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let coroutine = match tcx.type_of(fn_def).instantiate_identity().kind() {
context_before:     let return_ty = fn_sig.output();
context_after:         ty::Coroutine(_, args) => Some(Box::new(CoroutineInfo::initial(