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Description
Search Terms
- generator
- iterator
Suggestion
Express a fixed-length generator.
Use Cases
- Allows the spread syntax on functions to know how many arguments is deconstructed (see examples below)
Examples
// Vector2.ts
class Vector2 {
constructor (public x, public y) {
this.x = x;
this.y = y;
}
//... A bunch of vector methods
public* [Symbol.iterator]: Generator<number, void, unknown> {
yield this.x;
yield this.y;
}
}
// main.js
const canvas = document.querySelector('#canvas');
const ctx = canvas.getContext('2d');
const a = new Vector2(0, 0);
const b = new Vector2(10, 10);
ctx.beginPath();
ctx.moveTo(...a);
// works correctly, but with this warning:
// Expected 2 arguments, but got 0 or more.ts(2556)
ctx.lineTo(...b);
ctx.stroke();
ctx.closePath();
Right now, the code above produces the correct behavior. However, typescript doesn't not recognize how many arguments is passed to ctx.moveTo
and ctx.lineTo
therefore it warns me about it.
My Implementation
There could be an tuple-like syntax for generators as well, for example:
public* [Symbol.iterator]: *[number, number] {
yield this.x;
yield this.y;
}
With this syntax, typescript recognizes how many argument is deconstructed by the spread operator, and knows its a generator with the prepending *
.
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, etc.)
- This feature would agree with the rest of TypeScript's Design Goals.