Compile-time permutations in TypeScript

meta-permutations.ts

type Access<Tuple extends readonly unknown[], I extends string> =
    I extends keyof Tuple ? Tuple[I] : never

type Swap<Tuple extends readonly unknown[], I extends string, J extends string> = {
    [Index in keyof Tuple]: Index extends I ? Access<Tuple, J> : Index extends J ? Access<Tuple, I> : Tuple[Index] 
}

type Length<Tuple extends readonly unknown[]> = Tuple["length"] extends number ? `${Tuple["length"]}` : never

type PushFront<Tuple extends readonly unknown[], E> = [E, ...Tuple]

type Range<Size extends string, Tuple extends readonly unknown[] = []> = 
    Length<Tuple> extends Size ? Tuple : Range<Size, PushFront<Tuple, 0>>

type Increment<I extends string> = Length<PushFront<Range<I>, 0>>

type FixedIdx<Tuple extends readonly unknown[], I extends string, Idx extends string> =
    I extends Length<Tuple> ? Tuple : Perms<Swap<Tuple, I, Idx>, Increment<Idx>> | FixedIdx<Tuple, Increment<I>, Idx>

type Perms<Tuple extends readonly unknown[], Idx extends string> = 
    Idx extends Length<Tuple> ? Tuple : FixedIdx<Tuple, Idx, Idx>