Add a way to export class types without using ES6 class syntax about flow

[avikchaudhuri]

Yeah, we have some support for such things, but not entirely fleshed out. Try some like the following out and let's keep digging into what's missing.

declare class G {
x: number;
squared():number;
}

var Foo_: typeof G = Foo;
var c = new Foo_(0);
var y:string = c.squared();

This gives me a couple of type errors, which indicates that Flow is tracking the types around correctly:

funclass.js:4:37,42: number
This type is incompatible with
funclass.js:15:7,12: string

funclass.js:10:15,20: number
This type is incompatible with
funclass.js:15:7,12: string

Basically the trick is to use typeof to express the type of something for which you don't have surface syntax, but know that Flow may have an internal type representation.

[Raynos]

👍

It's incredibly hard to declare the type of a constructor function. I could not find any way to do it all; I tried everything from declare class to declare function to declare var

[samwgoldman]

Flow seems to understand @spicyj's original example now without any errors. Is there anything else remaining to be done here?

[Raynos]

@samwgoldman

can we have some examples of how to write a ES5 constructor and then how to write an declare block that declares it's type (preferably in one of those block comments that flow supports).

The use case here is to annotate a complex existing constructor with many methods using the unobtrusive block comment workflow.

[samwgoldman]

@Raynos It would be easier to start with what you have tried that didn't work. Can you share some code?

[Raynos]

@samwgoldman I can try and reproduce it; I worked on it a few weeks ago.

Let me update the thread with a breaking example tonight.

[samwgoldman]

@avikchaudhuri seems to have addressed @spicyj's original issue in 618186a. I think this can be closed.

[sophiebits]

Yes, thanks!