[Feature] Implement high-level `typeof` operator

[lorenzholzbauer]

Is there an existing proposal for this?

• [X] I have searched the existing issues

This feature does not exist in the latest version

• [X] I am using the latest version

Proposal

Add a typeof operator that returns the runtime object instead of a string like in JS.

For example:

• Null:

  var x: null = null;
  
  var y: type = typeof x; // -> null
  

• Primitives:

  var x: str = "x";
  
  var y: type = typeof x; // -> str
  

• Objects:

  interface X {
    prop: num
  }
  
  var x: X = {
    prop: 1
  };
  
  var y: type = typeof x; // -> obj  
  

• Arrays:

  var x: Array<num> = [1, 2, 3]
  
  var y: type = typeof x; // -> Array  
  

• Functions:

  var x: Func<num> = (): num -> {
    return 1;
  };
  
  var y: type = typeof x; // -> Func<num>
  

• Class:

  class Duck {
    ...
  }
  
  var x = new Duck();
  var y: type = typeof x; // -> Duck
  

Exact behaviour / changes you want

• [x] #659
• [x] Add typeof operator which is a built-in keyword that is separate from any references and such.
• [x] Add internal code structure required to evaluate the type of a variable at runtime.
• [x] Add type information to functions so they can also be used with typeof.
• [x] Add internal function typeof implementing the functionality for typeof.