Compiler: Option to create class extension methods.

[FunctionPoint]

@ezeaguerre suggested:
I also think that there's no easy way to add methods to a class, right?
Because, it would be nice to make "extensions", I don't know... something like:

EXTENSION Integer  
duplicate
    ^ self * 2.
!

[ezeaguerre]

About this one, I was thinking there are at least 2 possible ways to implement it:

We could actually change the original class, since everything is compiled together, we could open the original class file and add the methods in there (and instance variables, if any).

Otherwise, we could do it at runtime, generating some JS like this:

StInteger.prototype.$duplicate = function () {
  // generated code...
}

The last one needs to actually be loaded to trigger its side effect, otherwise the method never gets added.

As for instance variables (I don't know if you want to add instance variables to extensions), I don't know if there's a way to actually add an instance variable. But we could add getter/setters:

Object.defineProperty( StInteger.prototype, 'instanceVariableName', {
  get: function() {
    if (this.hasOwnProperty('instanceVariableName'))
      return this.instanceVariableName;
    return stNil;
  },
  set: function (newValue) {
    this.instanceVariableName = newValue;
  }
}

[ezeaguerre]

ok, I just looked at the Compiler class and it seems all the classes are loaded, ordered and then compiled... so we could generate only one class file with everything compiled in I guess. Right?

[FunctionPoint]

Yes, that last comment is right. :-)
The compiler compiles everyhing, so it just needs to compile any extension files after the original class header.
That can be ensured in the class ordering process before compilation:
The compiler is 2-pass: It first scans all class headers and then compiles their method bodies.
.
So it doesn't need to merge the files first.