{"ast_node_type":"variable","tokens":[{"end":80,"kind":"keyword","start":0,"text":"let"}]}
                        let b_offset = ImmTy::from_uint(b_offset, usize_layout);
                        let a_offset = ImmTy::from_uint(a_offset, usize_layout);
                        self.binary_op(BinOp::SubWithOverflow, &a_offset, &b_offset)?