ClojureScript

$ rlwrap ./script/repljs
"Type: " :cljs/quit " to quit"
#(assert (= "original" (let [x "original" 
                            oce (fn [] x) 
                            x "overwritten"] 
                        (oce))))
#<
function () {
    if (cljs.core._EQ_.call(null, "original", (function () {
        var x = "original";
        var oce = (function () {
            return x;
        });
        var x__$1 = "overwritten";
        return oce.call(null);
    })())) {
        return null;
    } else {
        throw (new Error([cljs.core.str("Assert failed: "), cljs.core.str(cljs.core.pr_str.call(null, cljs.core.with_meta(cljs.core.list("\ufdd1'=", "original", cljs.core.with_meta(cljs.core.list("\ufdd1'let", cljs.core.vec(["\ufdd1'x", "original", "\ufdd1'oce", cljs.core.with_meta(cljs.core.list("\ufdd1'fn", cljs.core.vec([]), "\ufdd1'x"), cljs.core.hash_map("\ufdd0'line", 14)), "\ufdd1'x", "overwritten"]), cljs.core.with_meta(cljs.core.list("\ufdd1'oce"), cljs.core.hash_map("\ufdd0'line", 16))), cljs.core.hash_map("\ufdd0'line", 13))), cljs.core.hash_map("\ufdd0'line", 13))))].join("")));
    }
}
>
#(letfn [(x [] "original") 
        (y [] (x))] 
  (let [x (fn [] "overwritten")] 
    (assert (= "original" (y)))))
#<
function () {
    var x = (function x() {
        return "original";
    });
    var y = (function y() {
        return x.call(null);
    });
    var x__$1 = (function () {
        return "overwritten";
    });
    if (cljs.core._EQ_.call(null, "original", y.call(null))) {
        return null;
    } else {
        throw (new Error([cljs.core.str("Assert failed: "), cljs.core.str(cljs.core.pr_str.call(null, cljs.core.with_meta(cljs.core.list("\ufdd1'=", "original", cljs.core.with_meta(cljs.core.list("\ufdd1'y"), cljs.core.hash_map("\ufdd0'line", 12))), cljs.core.hash_map("\ufdd0'line", 12))))].join("")));
    }
}
>

(do
  (let [x "original"]
    (defn original-closure-stmt [] x))

  (let [x "overwritten"]
    (assert (= "original" (original-closure-stmt))))