{"ast_node_type":"variable","tokens":[{"end":67,"kind":"keyword","start":0,"text":"let"}]}
        let Some(rhs_sum) = self.make_sum(rhs) else { return lhs };
    fn make_subtracted_sum(&mut self, lhs: CovTerm, rhs: &[CovTerm]) -> CovTerm {
        self.make_expression(lhs, Op::Subtract, rhs_sum)