Permit type alias declarations inside a class

I normally want my class declaration to be the first thing in my file:

module foo {

  /** My foo class */
  export class MyFoo {

  }
}

So when I want to declare an alias, I don't like the fact that my class has been pushed down further:

module foo {

 type foobar = foo.bar.baz.FooBar;

  /** My foo class */
  export class MyFoo {

  }
}

I suggest the following be permitted:

module foo {

  /** My foo class */
  export class MyFoo {
    type foobar = foo.bar.baz.FooBar;
  }
}

Since type foobar is just a compile-time construct, and if people want to write it that way, then they should be permitted to do so. Note that the type foobar is private to the class. It should not be permissible to export foobar.

The issue names no files, tests, or entry points. Start by reviewing the discussion and the existing rules for class members and type aliases; done means determining whether private type aliases inside classes should be accepted while exported aliases remain disallowed, with coverage for the examples described.