What purpose do the seemingly redundant length checks in TakeTwo<T> serve?

[specious]

I'm puzzled by the seemingly redundant { length: x | y | z } checks in the TakeTwo<T> type definition (which is like a padded slice(0, 2) for list types):

zustand/src/middleware/devtools.ts

Lines 30 to 48 in 51c00d2

	type TakeTwo<T> = T extends { length: 0 }
	? [undefined, undefined]
	: T extends { length: 1 }
	? [...a0: Cast<T, unknown[]>, a1: undefined]
	: T extends { length: 0 | 1 }
	? [...a0: Cast<T, unknown[]>, a1: undefined]
	: T extends { length: 2 }
	? T
	: T extends { length: 1 | 2 }
	? T
	: T extends { length: 0 | 1 | 2 }
	? T
	: T extends [infer A0, infer A1, ...unknown[]]
	? [A0, A1]
	: T extends [infer A0, (infer A1)?, ...unknown[]]
	? [A0, A1?]
	: T extends [(infer A0)?, (infer A1)?, ...unknown[]]
	? [A0?, A1?]
	: never

Even the AI assistant can't seem to find a case that slips through the direct checks for a length property of 0, 1 or 2 explicitly but then still gets caught by the catch-all.

@devanshj, I hate to bother you, but you're likely the best person to answer my question.

[dai-shi]

It was like that to support some old TS versions like 3.8. As of now, v5 dropped some old TS versions, so we might be able to simplify it a bit.

[specious]

Thank you so much for taking the time to shed some light on this.

If the code had comments explaining this caveat, it wouldn't be so confusing.

[devanshj]

See this comment and this PR description.

[dai-shi]

@specious Can you open a PR to add code comments?