//// [extendBooleanInterface.ts]
interface Boolean {
    doStuff(): string;
    doOtherStuff<T>(x: T): T;
}

var x = true;
var a: string = x.doStuff();
var b: string = x.doOtherStuff('hm');
var c: string = x['doStuff']();
var d: string = x['doOtherStuff']('hm');

//// [extendBooleanInterface.js]
var x = true;
var a = x.doStuff();
var b = x.doOtherStuff('hm');
var c = x['doStuff']();
var d = x['doOtherStuff']('hm');