Type JS's `arguments` object based on function parameters

Search Terms

type “arguments” object parameters

Suggestion

Within a function x, the type of the arguments object should be Parameters<typeof x> & IArguments, with undefined removed from the type of any entries in Parameters<typeof x> if that parameter has a default value.

Use Cases

class A {
   fn(it: number) { return true; }
}

class B extends A {
  fn(it: number) {
    // this shouldn't error, because arguments must be at least length 1.
    // instead we get ERROR: Expected 1 arguments, but got 0 or more.
    return super.fn(...arguments); 
  }
}

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.

[ElianCordoba]

Same problem here, I tried this but it didn’t work either

...
testFn(a, b, c) {
  const args = [...arguments].slice(0, 3);
  testFn(...args);
}
...

[chrmarti]

The strictBindCallApply feature makes the following show an error for passing arguments where an array is expected. That might be fixed by what is being discussed here as well.

function one(a: string, b: number) {

}

function two(a: string, b: number) {
	one.apply(null, arguments);
}