Strict Reflect.apply Reflect.construct and Function.prototype.apply/call/bind

Search Terms

Reflect.apply
Reflect.construct
Function.prototype.apply
Function.prototype.call
Function.prototype.bind

Suggestion

These functions should not return any.

Related:
https://github.com/microsoft/TypeScript/issues/212
https://github.com/microsoft/TypeScript/pull/27028

Use Cases

function getString() {
  return 'string'
}

class ClassA {}

Reflect.apply(getString, null, []) // expected string but got any
Reflect.construct(ClassA, []) // expected ClassA but got any
Function.prototype.apply.call(getString, undefined) // expected string but got any
Function.prototype.call.call(getString, undefined) // expected string but got any
Function.prototype.bind.call(getString, undefined)() // expected string but got any

Examples

Reflect:

// old
function apply(target: Function, thisArgument: any, argumentsList: ArrayLike<any>): any;

// new
function apply<T>(target: (...args: any) => T, thisArgument: any, argumentsList: ArrayLike<any>): T;

// old
function construct(target: Function, argumentsList: ArrayLike<any>, newTarget?: any): any;

// new
function construct<T>(target: new (...args: any) => T, argumentsList: ArrayLike<any>, newTarget?: any): T;

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
  👆 Add a new compiler option
• 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.

まず、Reflect.apply、Reflect.construct、Function.prototype.apply/call/bind の現在の宣言と、関連する型チェックテストを読みます。Issue で想定されている戻り値の型と比較し、一覧にある例が any ではなく string と ClassA を推論することを確認します。