Allow subclass constructors without super() call

TypeScript Version:

1.8.0

Code

Custom element classes often have constructors that just return document.createElement(), since HTMLElement doesn't have a callable constructor, but this generates an error in TypeScript:

class MyElement extends HTMLElement {
  constructor() {
    return document.createElement('my-element');
  }
}

In general, it is completely valid ES2015 to not call super(), as long as you don't access this.

issue 中没有指定文件或测试。首先定位针对省略 super() 的派生构造函数的 TypeScript 诊断，然后为 HTMLElement 示例添加回归测试覆盖，并验证不含 super() 或 this 访问的有效 ES2015 构造函数会被接受。