Add a way to annote `super` paramerter in objec literal.

Suggestion

🔍 Search Terms

super parameter object literal

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

We could using super in object literals:

var obj1 = {
  method1() {
    console.log('method 1');
  }
}

var obj2 = {
  method2() {
    super.method1();
  }
}

Object.setPrototypeOf(obj2, obj1);
obj2.method2(); // logs "method 1"

The value of super is determined at runtime, like this. And we already could explicit this parameter like following example`:

function f(this: void) {
  // make sure `this` is unusable in this standalone function
}

There could add a way to annote super paramerter in objec literal:

let parent = { /* some props */ }
let child = {
  method1(super: typeof parent){
    // 
  }
}

It won't break the existing codes we aleary have, cause super is a keyword, we can't use it as a formal argument.

📃 Motivating Example

When extends some object provide by runtime enviroment which have no constructor for us to extend, we can do this:

before:

function patchA(origin: IOrigin){
   let patch = {
      mehtod1(arg: any){
           // do some compability work
           origin.method1(arg);
      },
      //...
  }
  return Object.setPrototypeof(patch, originObj);
}

function patchB(origin: IOrigin){
   let patch = {
      mehtod1(arg: any){
           // do some compability work
           origin.method1(arg);
      },
      //...
  }
  return Object.setPrototypeof(patch, originObj);
}

after:

let patchA = {
    mehtod1(super: IOrigin, arg: any){
           // do some compability work
           // type friendly to use super here
           super.method1(arg);
      },
}
let patchB = {
    mehtod1(super: IOrigin, arg: any){
           // do some compability work
           // type friendly to use super keyword here
           super.method1(arg);
      },
}

function doPatch(patch, origin: IOrigin){
  return Object.setPrototypeof(patch, origin);
}

💻 Use Cases

I'm writing a lib about canvas now, it run on multiple platforms, web, weixin-miniprogram, uniapp-h5, uniapp-mp-weixin...

There is some difference on canvas context api. Additionally, same api on different platform are act slightly different.

In web, canvas context's interface is CanvasRenderingContext2D, in wieixn-miniprogram and uniapp, context's interface is CanvasContext. In my lib, it's PainterContext which is much like CanvasContext.

First, I try to use adptor pattern to handle this.

class PainterH5Context extends CanvasRenderingContext2D implements PainterContext {
  async drawImage(imageResource: string, sx: number, sy: number){
    const imageElement = await createImageElement(imageResource);
    super.drawImage(imageResource: string, sx: number, sy: number);
  }
}

but, new a CanvasRenderingContext2D instance is forbid in browser, It also violate the rule that child class should implement parent's all interface, casue signature of drawImage were different.

So I directly handle prototype chain.

function patchH5Context (context: CanvasRenderingContext2D): PainterContext {
  let patch = {
      async drawImage(imageResource: string, sx: number, sy: number){
        const imageElement = await createImageElement(imageResource);
        context.drawImage(imageResource, sx, sy);
    }
  }
  // use createExtendableContextProto to make methods on contenxt bind context itself
  // otherwise it with rise an error when invoke
  return Object.setPrototypeof(patch, createExtendableContextProto(context));  
}

I want extract the patch object out of the function. cause function logic are same on different platforms.
To implement that I use the super keyword, but I can't get any type intellesence:

let h5ContextPatch = {
     async drawImage(imageResource: string, sx: number, sy: number){
        const imageElement = await createImageElement(imageResource);
        super.drawImage(imageElement, sx, sy);
    }
}
let UniContextPatch = {
     async drawImage(imageResource: string, sx: number, sy: number){
        const tempPath = await dowloadFiles(imageResource);
        super.drawImage(tempPath, sx, sy);
    }
}

function doPatch(patch: Partial<PainterContext>, context: CanvasRenderingContext2D | CanvasContext){
  return Object.setPrototypeof(patch, createExtendableContextProto(context));
}

La charge utile ne nomme aucun fichier du dépôt, test ou point d’entrée par lequel commencer. Avant l’implémentation, la proposition a besoin d’une conception concrète et de tests d’acceptation pour saisir super dans des méthodes de littéral d’objet, y compris les exemples montrés de modification de prototypes.