The Tor Browser / file revision

 // The decompiler correctly handles for-of loops.

 function tokens(code) {

     var arr = [];

     var s = code.replace(/\w+|[^\s]/g, function (tok) { arr.push(tok); return ""; });

     assertEq(s.trim(), "", "tokens() should find all tokens in code: " + uneval(code));

     return arr;

 }

 function test(code) {

     var before = "function f() { " + code + " }";

     var after = eval("(" + before + ")").toString();

     assertEq(tokens(before).join(" "), tokens(after).join(" "), "decompiler failed to round-trip");

 }

 // statements

 test("for (a of b) { f(a); }");

 test("for (a of b) { f(a); g(a); }");

 // for-of with "in" operator nearby

 test("for (a of b in c ? c : c.items()) { f(a); }");

 // destructuring

 test("for ([a, b] of c) { a.m(b); }");

 // for-let-of

 test("for (let a of b) { f(a); }");

 test("for (let [a, b] of c) { a.m(b); }");

 // array comprehensions

 test("return [a for (a of b)];");

 test("return [[b, a] for ([a, b] of c.items())];");

 // generator expressions

 test("return (a for (a of b));");