Decorated computed properties in class fail

[ivogabe]

Multiple computed properties with decorators fail using 1.5.0-alpha:

declare function decorate();
class Foo {
    @decorate
    ["name-1"]() {}
    @decorate
    ["name-2"]() {}
}

Compiles to

var Foo = (function () {
    function Foo() {
    }
    Foo.prototype[_a = "name-1"] = function () { };
    Foo.prototype[_a] = function () { };
    Object.defineProperty(Foo.prototype, _a, __decorate([decorate], Foo.prototype, _a, Object.getOwnPropertyDescriptor(Foo.prototype, _a)));
    Object.defineProperty(Foo.prototype, _a, __decorate([decorate], Foo.prototype, _a, Object.getOwnPropertyDescriptor(Foo.prototype, _a)));
    return Foo;
    var _a;
})();

Note that both methods use temporary variable _a and only "name-1" is emitted in the javascript. The result should be:

var Foo = (function () {
    function Foo() {
    }
    Foo.prototype[_a = "name-1"] = function () { };
    Foo.prototype[_b = "name-2"] = function () { };
    Object.defineProperty(Foo.prototype, _a, __decorate([decorate], Foo.prototype, _a, Object.getOwnPropertyDescriptor(Foo.prototype, _a)));
    Object.defineProperty(Foo.prototype, _b, __decorate([decorate], Foo.prototype, _b, Object.getOwnPropertyDescriptor(Foo.prototype, _b)));
    return Foo;
    var _a, _b;
})();

[rbuckton]

Fixed by #2662