delegating-yield-3.js

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// Test yield* with iter.next and monkeypatching.

function* g(n) { for (var i=0; i<n; i++) yield i; }

function* delegate(iter) { return yield* iter; }

var GeneratorObjectPrototype = Object.getPrototypeOf(g).prototype;

var GeneratorObjectPrototype_next = GeneratorObjectPrototype.next;

// Monkeypatch next on an iterator.

var inner = g(20);

var outer = delegate(inner);

var innerNextFn = GeneratorObjectPrototype_next;

inner.next = function() { return innerNextFn.call(this); };

assertIteratorNext(outer, 0);

assertIteratorNext(outer, 1);

innerNextFn = function() { return { patched: true }; };

// 42 yielded directly without re-boxing.

assertEq(true, outer.next().patched);

// Outer generator not terminated.

assertEq(true, outer.next().patched);

// Restore.

innerNextFn = GeneratorObjectPrototype_next;

assertIteratorNext(outer, 2);

// Repatch.

innerNextFn = function() { return { value: 42, done: true }; };

assertIteratorDone(outer, 42);

// Monkeypunch next on the prototype.

var inner = g(20);

var outer = delegate(inner);

var innerNextFn = GeneratorObjectPrototype_next;

GeneratorObjectPrototype.next = function() { return innerNextFn.call(this); };

assertIteratorNext(outer, 0);

assertIteratorNext(outer, 1);

innerNextFn = function() { return { patched: true }; };

// 42 yielded directly without re-boxing.

assertEq(true, GeneratorObjectPrototype_next.call(outer).patched);

// Outer generator not terminated.

assertEq(true, GeneratorObjectPrototype_next.call(outer).patched);

// Restore.

innerNextFn = GeneratorObjectPrototype_next;

assertIteratorNext(outer, 2);

if (typeof reportCompare == "function")

    reportCompare(true, true);