conversions.js - mozsearch

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// Section numbers cite ES6 rev 24 (2014 April 27).

var symbols = [

    Symbol(),

    Symbol("one"),

    Symbol.for("two"),

    Symbol.iterator

];

function testSymbolConversions(sym) {

    // 7.1.2 ToBoolean

    assertEq(Boolean(sym), true);

    assertEq(!sym, false);

    assertEq(sym || 13, sym);

    assertEq(sym && 13, 13);

    // 7.1.3 ToNumber

    assertThrowsInstanceOf(() => +sym, TypeError);

    assertThrowsInstanceOf(() => sym | 0, TypeError);

    // 7.1.12 ToString

    assertThrowsInstanceOf(() => "" + sym, TypeError);

    assertThrowsInstanceOf(() => sym + "", TypeError);

    assertThrowsInstanceOf(() => "" + [1, 2, sym], TypeError);

    assertThrowsInstanceOf(() => ["simple", "thimble", sym].join(), TypeError);

    // 21.1.1.1 String()

    assertEq(String(sym), sym.toString());

    // 21.1.1.2 new String()

    assertThrowsInstanceOf(() => new String(sym), TypeError);

    // 7.1.13 ToObject

    var obj = Object(sym);

    assertEq(typeof obj, "object");

    assertEq(Object.prototype.toString.call(obj), "[object Symbol]");

    assertEq(Object.getPrototypeOf(obj), Symbol.prototype);

    assertEq(Object.getOwnPropertyNames(obj).length, 0);

    assertEq(Object(sym) === Object(sym), false);  // new object each time

    var f = function () { return this; };

    assertEq(f.call(sym) === f.call(sym), false);  // new object each time

for (var sym of symbols) {

    testSymbolConversions(sym);

    // 7.1.1 ToPrimitive

    var symobj = Object(sym);

    assertThrowsInstanceOf(() => Number(symobj), TypeError);

    assertThrowsInstanceOf(() => String(symobj), TypeError);

    assertThrowsInstanceOf(() => symobj < 0, TypeError);

    assertThrowsInstanceOf(() => 0 < symobj, TypeError);

    assertThrowsInstanceOf(() => symobj + 1, TypeError);

    assertThrowsInstanceOf(() => "" + symobj, TypeError);

    assertEq(sym == symobj, true);

    assertEq(sym === symobj, false);

    assertEq(symobj == 0, false);

    assertEq(0 != symobj, true);

    // 7.1.12 ToString

    assertThrowsInstanceOf(() => String(Object(sym)), TypeError);

// Deleting Symbol.prototype[@@toPrimitive] does not change the behavior of

// conversions from a symbol to other types.

delete Symbol.prototype[Symbol.toPrimitive];

assertEq(Symbol.toPrimitive in Symbol.prototype, false);

testSymbolConversions(symbols[0]);

// It does change the behavior of ToPrimitive on Symbol objects, though.

// It causes the default algorithm (OrdinaryToPrimitive) to be used.

var VALUEOF_CALLED = 117.25;

Symbol.prototype.valueOf =  function () { return VALUEOF_CALLED; };

Symbol.prototype.toString = function () { return "toString called"; };

for (var sym of symbols) {

    var symobj = Object(sym);

    assertEq(Number(symobj), VALUEOF_CALLED);

    assertEq(String(symobj), "toString called");

    assertEq(symobj < 0, VALUEOF_CALLED < 0);

    assertEq(0 < symobj, 0 < VALUEOF_CALLED);

    assertEq(symobj + 1, VALUEOF_CALLED + 1);

    assertEq("" + symobj, "" + VALUEOF_CALLED);

    assertEq(symobj == 0, false);

    assertEq(0 != symobj, true);

if (typeof reportCompare === "function")

    reportCompare(0, 0);