LiteralList<Union>

[macmillen]

I want to be able to define an array that contains exactly the elements of all possible values of a union once.

type Union = "prevStep" | "nextStep" | "submit" | "order";

// this works:
const list: LiteralList<Union> = ["nextStep", "order", "prevStep", "submit"];

// this fails:
const list: LiteralList<Union> = ["nextStep", "order", "prevStep", "submit", "submit"];

// this fails:
const list: LiteralList<Union> = ["nextStep", "order", "prevStep"];

I already made this work with this type:

type LiteralList<T extends string, U = T> = [T] extends [never]
  ? []
  : U extends T
  ? [U, ...LiteralList<Exclude<T, U>>]
  : [];

I'm not sure though if it makes sense since I asked ChatGPT to do it.

Is it possible to add this type helper to type-fest?

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[macmillen]

I realized that this:

type LiteralList<T extends string, U = T> = [T] extends [never]
  ? []
  : U extends T
  ? [U, ...LiteralList<Exclude<T, U>>]
  : [];

for some reason is really slowing down the TS language server.

Is there maybe another way to achieve this?

[Emiyaaaaa]

Related to #686