TypeScript: Class Inheritance is Not ES6 Spec Compliant

The following should log true but logs false instead:

class Foo {}
class Bar extends Foo {}

console.log(Object.getPrototypeOf(Bar) === Foo);

This is due to how the __extends helper is implemented. It generates this:

var __extends = this.__extends || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};

An example of a correctly functioning extends implementation can be found in the 6to5 compiler. Here is their implementation:

var _extends = function (child, parent) {
    child.prototype = Object.create(parent.prototype, {
      constructor: {
        value: child,
        enumerable: false,
        writable: true,
        configurable: true
      }
    });
    child.__proto__ = parent;
  };