Allow call signatures on classes

[rjamesnw]

From here: https://typescript.codeplex.com/workitem/2464

I have a possible solution: Just allow this:

class A {
    [index: number]: A; // <- since you can already do this
    (...args): A; // <- why not allow this also?
    constructor(...args) { }
}

Other suggestion by fdecampredon was:

class A {
  (): string {
    //do something
    return 'hello world';
  }
  constructor(): A {
    //do something else
  }
}

could be transformed into that :

function A() {
  if (!(this instanceof A)) {
    //do something
    return 'hello world';
  } else {
    //do something else
  }
}

[ahejlsberg]

I'm warming up to the idea of allowing call signatures to be part of a class declaration. I think it would be meaningful to consider them a new form of overload of the constructor and validate (by some new rule) that the constructor implementation signature satisfies the contract implied by both kinds of overload signatures (just like we do with regular overloads).

I don't think automatically injecting instanceof checks in the constructor implementation is a good idea. I think it should be up to the programmer to implement the check in whichever way is desired, similar to regular overloads.

[rjamesnw]

Thanks Anders! Bless your heart. ;)

[fdecampredon]

There is already a similar issue #183

[RyanCavanaugh]

Thanks for the pointer to 183 -- closing as duplicate.

[rjamesnw]

Ok, thanks. I did search for an existing request, and nothing came up, not sure how I missed it.