Sorry for the late reply, didn't have time to investigate further.

I am by no means an advanced TS user, so I don't have a ready solution, but would like to share my findings.

It seems that original ramda's prop was made to accept numbers as property input to better follow JS behavior (which seems reasonable)

And indeed, a special handling of numbers for prop was added.

I see that rambda's implementation have array indexing ootb support as well.

Now, this code works in both libraries:

const t = prop(0, [100]); //=> 100

Here it compiles with the following overload matching:

export function prop<P extends keyof T, T>(propToFind: P, obj: T): T[P];

And indeed, keyof number[] = number | "length" | ....

So it seems that no harm is done by using array indexing via prop - it is supported by both JS and TS implementation, mentioned in the docs and is in there by design.

Now, getting back to curried version.

While aforementioned uncurried type overload allows for arbitrary P extending keyof T, curried versions don't, they expect strings only:

export function prop<P extends string>(p: P): <T>(obj: Record<P, T>) => T;
export function prop<P extends string, T>(p: P): (obj: Record<P, T>) => T;

Something along the lines of this would be great to have:

export function prop<P extends keyof T, T>(p: P): (propToFind: P) => T[P];

But this overload only works with explicit types provided (this seems to be an inference limitation):

const myAccessor = prop<keyof MyObjType, MyObjType>(0);

Seems repeating, and ugly?

So, just adding number might not be the worst solution for the time being, and it certainly tracks usage and implementation better:

prop<P extends string | number>(p: P): <T>(propToFind: Record<P, T>) => T;
prop<P extends string | number, T>(p: P): (propToFind: Record<P, T>) => T;

Ramda typings leave much to be desired, both old and new, it might be worth it to deviate from them with good reasons.

Possible currying glitch #553

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