chore(typings): improve zip typings

[cartant]

Add signature to the lettable zipProto so it's consistent with the
non-lettable zipProto.

Description:

This PR is closely related to #2787. In between that PR being submitted and its being merged there were WIP commits made re: lettable operators. Consequently, the overload signature that the PR added to the non-lettable zipProto was not included in the lettable zipProto.

This PR adds the relevant overload to the lettable zipProto.

Related issue (if exists): #2784

[cartant]

Unfortunately, this PR falls victim to TypeScript matching arbitrary functions with ArrayLike<any> and, consequently, with ObservableInput<any>. That means that if T is any there is no sensible order for:

export function zip<T>(...observables: Array<ObservableInput<T>>): OperatorFunction<T, T[]>;

and:

export function zip<T, R>(...observables: Array<ObservableInput<T> | ((...values: Array<T>) => R)>): OperatorFunction<T, R>;

When T is any whichever is first will be matched regardless of whether or not a projection function is specified.

This is a pity, as when T is not any it works fine. Such is life.

This also means that the signature added in PR #2787 is also unsafe when T is any and should probably be removed.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.