{"ast_node_type":"variable","tokens":[{"end":55,"kind":"keyword","start":0,"text":"let"}]}
                let lhs_ty = self.check_expr(lhs_expr);
                // in `&'a T <: &'x T` and `&'b T <: &'x T`, instead of `'a = 'b = 'x`.
                let fresh_var = self.next_ty_var(lhs_expr.span);