src/third_party/mozjs-45/js/src/jit-test/tests/collections/WeakSet-constructor.js

var list = [Number, Function];

var ws = new WeakSet(list);
assertEq(ws.has(Number), true);
assertEq(ws.has(Function), true);

ws = new WeakSet(new Set(list));
assertEq(ws.has(Number), true);
assertEq(ws.has(Function), true);