Feature Request: type for Arguments OF Function

Search Terms

Suggestion

current typescript support ...args
but when we use

declare function a(x: number, y: number) : number
declare function a(x: number, s: string) : string

a(...[1, 2]) // => Error: TS2556: Expected 2 arguments, but got 0 or more.

will get error

Use Cases

Examples

declare function a(x: number, y: number) : number
declare function a(x: number, s: string) : string

Actual behavior:

a(...[1, 2]) // => Error: TS2556: Expected 2 arguments, but got 0 or more.

type ArgumentsOFFunction<T extends Function>

a type can let typescript know this is args array of target function

notice: this type is not exists

Expected behavior:

let args1: ArgumentsOFFunction<typeof a> = [x = 1, s = ''];
let args2: ArgumentsOFFunction<typeof a> = [x = 1, y = 2];
let args3: ArgumentsOFFunction<typeof a> = ['1', 2]; // trigger a ts error => Error: TS2345: Argument of type '"1"' is not assignable to parameter of type 'number'.

a(...args1) // => string
a(...args2) // => number

a(1, 'str') // => string
a(1, 2) // => number

a('1', 2) // trigger a ts error => Error: TS2345: Argument of type '"1"' is not assignable to parameter of type 'number'.

declare function b(...args: ArgumentsOFFunction<typeof a>) : boolean

b(...args1) // => boolean
b(...args2) // => boolean

b(1, 'str') // => boolean
b(1, 2) // => boolean

b('1', 2) // trigger a ts error => Error: TS2345: Argument of type '"1"' is not assignable to parameter of type 'number'.

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.

issue にはファイル、テスト、またはコンパイラのエントリポイントが記載されていません。まず、オーバーロードされた関数、タプル引数、ジェネリックな rest パラメーターについて意図された動作を明確にし、次に、提案された ArgumentsOFFunction 型、有効な呼び出し、示されている型エラーをカバーするコンパイラテストを追加してください。