typescript: correct on helper types

[otonashixav]

refactor: correct on helper types

• Previous input type now includes undefined, which is its initial value
• When defer is true, memos created with the on helper include undefined
• Fixed return type becoming unknown when passing a function with a third parameter (the previous type)
• Allow readonly arrays/tuples to be passed as deps
• Disallow empty arrays from being passed as deps
• Breaks backwards compatibility of the first generic; now it is the type of the inputs passed to the function instead of the type of the deps themselves:

// before
on<number>(() => 1, ...) // error
on<() => number>(() => 1, ...) // ok
on<[number]>([() => 1], ...) // error
on<[() => number]>([() => 1], ...) // ok

// now
on<number>(() => 1, ...) // ok
on<() => number>(() => 1, ...) // error
on<() => number>(() => () => 1, ...) // ok
on<[number]>([() => 1], ...) // ok
on<[() => number]>([() => 1], ...) // error
on<[() => number]>([() => () => 1], ...) // ok

This matches how createResource's source parameter works, and is simpler. However if #935 cannot be typed in this way, it might be better to revert to the more complex method of using S as the type of deps, and then to map it accordingly. It would be best to wait and see how the discussion there pans out before merging this.

[coveralls]

Pull Request Test Coverage Report for Build 2252897040

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.004%) to 89.476%

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Totals
Change from base Build 2223127986:	-0.004%
Covered Lines:	1216
Relevant Lines:	1295

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💛 - Coveralls