Declaration merging: remove function overloads?

Let's say one of the libs come with a function like this:

// library:
declare module 'example' {
    interface Animal { }
    export function sayHello(a: Animal);
}

I want to narrow down the type to just Dog. This is my module augmentation:

// app.ts
declare module 'example' {
    interface Dog extends Animal { }
    export function sayHello(a: Dog);
}

This merges the declarations to two function overloads:

sayHello(a: Dog);
sayHello(a: Animal);

I'd like to remove the generic Animal one to get stricter type checking of my code.

I couldn't find if this has been discussed before but I would find it useful quite often. Some examples would be:

• express headers (string by default, I'd use union of string literals)
• yargs args (I'd limit them to args specific to my app)

Empieza estudiando los ejemplos de declaration-merging y module-augmentation del issue, incluido el comportamiento de las sobrecargas para express headers y yargs args. Se considera terminado cuando exista una forma compatible de eliminar o restringir la sobrecarga genérica original, con una comprobación más estricta para el tipo aumentado.