syntax_data: {"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let (new, oflo) = val.checked_add(tcx, 1);
context_before:             assert_eq!(self.to_ty(tcx), val.ty);
context_after:             if oflo { None } else { Some(new) }