Prefer union type parameters instead of function overloads

[rveerd]

lib Update Request

The type definitions for String.replace and String.replaceAll are written using overloads. Should they not be written with union type parameters?

Overloads give problems when creating wrapper functions for String.replace; see example below.

This has already been proposed in this comment in another issue but I cannot find a follow-up issue or discussion.

The documentation describes a similar problem and also advises to prefer union types, when possible.

Sample Code

export class Foo {
  constructor(
    private name: string
  ) { }

  replace(searchValue: RegExp | string, replaceValueOrReplacer: string | ((substring: string, ...args: any[]) => string)): string {
    return this.name.replace(searchValue, replaceValueOrReplacer);
  }
}

src/stream.ts:7:43 - error TS2769: No overload matches this call.
  The last overload gave the following error.
    Argument of type 'string | ((substring: string, ...args: any[]) => string)' is not assignable to parameter of type '(substring: string, ...args: any[]) => string'.
      Type 'string' is not assignable to type '(substring: string, ...args: any[]) => string'.

7     return this.name.replace(searchValue, replaceValueOrReplacer);
                                            ~~~~~~~~~~~~~~~~~~~~~~

  node_modules/typescript/lib/lib.es5.d.ts:454:5
    454     replace(searchValue: string | RegExp, replacer: (substring: string, ...args: any[]) => string): string;
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The last overload is declared here.

[IllusionMH]

Looks like duplicate of #44919.

And related request that should resolve it in general case #17471

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.