js/src/jit-test/tests/for-of/semantics-07.js


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// Deleting the .next method of an iterator in the middle of a for-of loop
// causes a TypeError at the next iteration.

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

var iterProto = Object.getPrototypeOf([][Symbol.iterator]());
var s = '';
assertThrowsInstanceOf(function () {
    for (var v of ['duck', 'duck', 'duck', 'goose', 'FAIL']) {
        s += v;
        if (v === 'goose')
            delete iterProto.next;
        s += '.';
    }
}, TypeError);
assertEq(s, 'duck.duck.duck.goose.');