[expect-type]: Allow negation of toBeCallableWith

[GerkinDev]

I've noticed it's impossible to check for a function to not be callable with arguments

https://github.com/mmkal/ts/blob/main/packages/expect-type/src/index.ts#L111

In case of negated assertion, the check property is never.

So. I've tweaked around and I think the issue is that typing errors are generated during the last call, where type parameters are merged to generate a MISMATCH, spread as a rest parameter to generate type that can never be instantiated properly. But the current format of toBeCallableWith already takes a rest parameter for args.

So, here is the proposal: create a new method that takes arguments not as a rest tuple, but as a single tuple. Something like this:

export interface ExpectTypeOf<Actual, B extends boolean> {
    toBeCallableWithArgs: <T extends any[] | [never]>(args: T, ...MISMATCH: MismatchArgs<Extends<T, Params<Actual>>, B>) => true;
}

Thoughts ?

[mmkal]

Yes, this would be nice, but unfortunately breaks down for overloaded functions. I'll leave this open so it can be documented better, but basically - you'll have to use @ts-expect-error.

[aryaemami59]

@mmkal I think I'm gonna give this a shot, it might be a good new feature for v1.