iterator-proto-surfaces.js

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// Iterator prototype surfaces.

load(libdir + "asserts.js");

load(libdir + "iteration.js");

var iterProto = null;

function test(constructor) {

    var iter = new constructor()[Symbol.iterator]();

    assertDeepEq(Reflect.ownKeys(iter), []);

    // Iterator prototypes only have a .next and @@toStringTag property.

    var proto1 = Object.getPrototypeOf(iter);

    assertDeepEq(Reflect.ownKeys(proto1), ['next', Symbol.toStringTag]);

    var desc = Object.getOwnPropertyDescriptor(proto1, 'next');

    assertEq(desc.configurable, true);

    assertEq(desc.enumerable, false);

    assertEq(desc.writable, true);

    // %IteratorPrototype%

    var proto2 = Object.getPrototypeOf(proto1);

    assertEq(Object.getPrototypeOf(proto2), Object.prototype);

    assertEq(Object.prototype.toString.call(proto2), "[object Iterator]");

    var expectedKeys = ["map", "filter", "take", "drop", "flatMap", "reduce", "toArray",

                        "forEach", "some", "every", "find", "constructor",

                        Symbol.iterator, Symbol.toStringTag];

    if (getBuildConfiguration("explicit-resource-management")) {

      expectedKeys.splice(expectedKeys.length - 1, 0, Symbol.dispose);

    assertDeepEq(Reflect.ownKeys(proto2), expectedKeys);

    assertEq(proto2[Symbol.iterator](), proto2);

    // Check there's a single %IteratorPrototype% object.

    if (iterProto === null)

	iterProto = proto2;

    else

	assertEq(iterProto, proto2);

test(Array);

test(String);

test(Map);

test(Set);