{"ast_node_type":"variable","tokens":[{"end":42,"kind":"keyword","start":0,"text":"let"}]}
            let rhs_ty = self.parse_ty()?;
        } else if self.eat(exp!(Eq)) || self.eat(exp!(EqEq)) {
            Ok(ast::WherePredicateKind::EqPredicate(ast::WhereEqPredicate { lhs_ty: ty, rhs_ty }))