src/third_party/mozjs-45/js/src/jit-test/tests/for-of/proxy-3.js

// An exception thrown from a proxy trap while getting the .iterator method is propagated.

load(libdir + "asserts.js");
load(libdir + "iteration.js");

var p = Proxy.create({
    getPropertyDescriptor: function (name) {
        if (name == Symbol.iterator)
            throw "fit";
        return undefined;
    }
});
assertThrowsValue(function () { for (var v of p) {} }, "fit");