Type Alias _CollapseRestElement<TArray, ForwardAccumulator, BackwardAccumulator>

_CollapseRestElement: TArray extends UnknownArray
    ? "0" extends keyof TArray
        ? TArray extends readonly [(infer First)?, ...(infer Rest)]
            ? _CollapseRestElement<
                Rest,
                [
                    ...ForwardAccumulator,
                    TArray extends readonly [unknown, ...unknown[]]
                        ? First
                        : If<IsExactOptionalPropertyTypesEnabled, First, First | undefined>,
                ],
                BackwardAccumulator,
            >
            : never
        : TArray extends readonly [...(infer Rest), infer Last]
            ? _CollapseRestElement<
                Rest,
                ForwardAccumulator,
                [Last, ...BackwardAccumulator],
            >
            : TArray extends readonly []
                ? [...ForwardAccumulator, ...BackwardAccumulator]
                : [...ForwardAccumulator, TArray[number], ...BackwardAccumulator]
    : never