call-constructors.md

Call constructor should be static and inherited

I'd like to argue that call constructors should behave like static methods and be inherited, because it would be surprising if they didn't.

Here's a use case:

We can currently use static methods to instantiate classes, as an alternative to new:

class Base {
  static create() { return new this(); }
}

class Sub extends Base {
}

console.log(new Sub);      // => Sub instance
console.log(Sub.create()); // => Sub instance (same)

Note that we use this to access the class, and that create is inherited.

Looking at this example, it seems reasonable to extrapolate that Sub() would be a static method call just like Sub.create().

This would mean that we can rewrite the .create method to be a call constructor like so:

// My proposed behavior:

class Base {
  call constructor() { return new this(); }
}

class Sub extends Base {
}

console.log(new Sub);      // => Sub instance
console.log(Sub());        // => Sub instance (same)

The current spec doesn't seem to allow for this. It seems that maybe it should.

P.S. If we do decide to make call constructors static and inherited, then maybe we should consider renaming them to better reflect this - I sketched out some ideas. This is just a nitpick though. I mostly care about getting the semantics right.

Gist doesn't notify me about comments - let's use Twitter to discuss: https://twitter.com/jo_liss/status/656485512576946176