title: How does prototype extend on typescript?
body: <p>i extended function prototype but typescript doesn't recognize it.</p>
  
  <pre><code>Function.prototype.proc = function() {
    var args, target, v;
    var __slice = [].slice;
    args = 1 &lt;= arguments.length ? __slice.call(arguments, 0) : [];
    target = this;
    while (v = args.shift()) {
      target = target(v);
    }
    return target;
  };
  // generated by coffee-script
  
  var foo: (number) =&gt; (string) =&gt; number
    = (a) =&gt; (b) =&gt; a * b.length;
  console.log(foo.proc("first", "second"))
  </code></pre>
  
  <p>result: tsc -e</p>
  
  <pre><code>The property 'proc' does not exist on value of type 'Function'
  </code></pre>
  
  <p>how do i extend this object?</p>