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

[BlackGlory]

Search Terms

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

Suggestion

These functions should not return any.

Related:
#212
#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.

[jablko]

I'd expect Function.prototype.apply(null, getString); to error, like (Function.prototype as CallableFunction).apply(null, getString);:

error TS2684: The 'this' context of type 'CallableFunction' is not assignable to method's 'this' of type '(this: any, ...args: any[]) => unknown'.
  Type 'CallableFunction' provides no match for the signature '(this: any, ...args: any[]): unknown'.

--stringBindCallApply should apply the CallableFunction interface to the Function global as well as to function instances?

[BlackGlory]

The original use case code has an error and has been fixed.

Since Reflect.apply is easier to use than Function.prototype.apply and Reflect.construct provides feature that Function.prototype does not have, maybe we don't need to apply CallableFunction interface to Function, we just need to improve Reflect.apply and Reflect.construct.

[jablko]

Just checking whether the spread operator available to you?

const args = [];
new ClassA(...args); // ClassA

[BlackGlory]

This is not an issue about how to dynamically create an object instance.

[jablko]

Would you consider adding more information about your use case?

[zanminkian]

This issue is equivalent to say: add type guard for Reflect.apply under --strictBindCallApply.

Example:

function foo(name: string) {
  console.log(name)
}

foo.apply(null, [42]); // typescript will report type error, great!
Function.prototype.apply.call(foo, null, [42]); // no error 😢
Reflect.apply(foo, null, [42]); // no error 😢