Problem statement

I would like to start with an interface that has many overloaded call signatures, and replace one of them with a different signature. This means that I have to omit a particular signature from the base interface before adding its replacement.

Goal

Presume that I start with this interface:

interface Foo {
  (options: {method: 'authorize', userId: number}): Promise<string>;
  (options: {method: 'deauthorize', authToken: string}): Promise<boolean>;
}

And I want to end with this interface:

interface Bar {
  (options: {method: 'authorize', userToken: string}): Promise<string>; // NEW
  (options: {method: 'deauthorize', authToken: string}): Promise<boolean>; // UNALTERED
}

What I've tried

I tried to use the Exclude utility type to remove the unwanted signature.

type BaseInterface = Exclude<Foo, (options: {method: 'authorize', userId: number}) => Promise<string>>;

interface Bar extends BaseInterface {
  (options: {method: 'authorize', userToken: string}): Promise<string>;
}

…but that just resulted in BaseInterface being of type never.