syntax_data: {"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let ty::Adt(_poll_adt, args) = *self.old_yield_ty.kind() else { bug!() };
context_before:             CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, _) => {
context_after:                 let ty::Adt(_option_adt, args) = *args.type_at(0).kind() else { bug!() };