Downlevel destructuring for parameter properties emits incorrectly

[DanielRosenwasser]

class C {
    constructor(public [x, y, z]: string[]) {
    }
}

Emitted code:

var C = (function () {
    function C(_a) {
        var x = _a[0], y = _a[1], z = _a[2];
        this.[x, y, z] = [x, y, z];
    }
    return C;
})();

Clearly this.[x,y,z] is not legal.

[mhegazy]

Based on our offline discussion, this should not be allowed.