src/third_party/mozjs-45/js/src/jit-test/tests/collections/WeakMap-constructor-generator-3.js

// The argument to WeakMap may be a generator-iterator that produces no values.

new WeakMap(x for (x of []));

function none() {
    if (0) yield 0;
}
new WeakMap(none());

function* none2() {
    if (0) yield 0;
}
new WeakMap(none2());