syntax_data: {"ast_node_type":"variable","tokens":[{"end":53,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let (rhs_ty, rhs) = self.unop_args();
context_before:             ty::ExprKind::UnOp(op) => {
context_after:                 write!(f, "({op:?}: ({:?}: {:?}))", rhs, rhs_ty)