Make LiteralUnion type work for more types

[kripod]

While experimenting with automatic prop completion for an upcoming CSS-in-JS library, I wanted to use LiteralUnion as follows:

import { CSSProperties } from 'react';

enum Duration {
  SHORT = 1, // Gets resolved to a string somewhere else in the code
  LONG,
}

type AnimationDurationValue = LiteralUnion<
  Duration,
  CSSProperties['animationDuration']
>;

LiteralUnion works perfectly when LiteralType doesn't extend BaseType.

[sindresorhus]

// @BendingBender

[kripod]

I would like to ask for a status update on this. Thank you for reviewing in advance!

Until then, here is a real world use-case: https://github.com/kripod/glaze/blob/c363cf3986f595a2759fedb08030f88e40e6ad7b/packages/glaze/src/useStyling.ts#L82-L96

[sindresorhus]

I haven't had a chance to look into this yet. I'm thinking there must be a reason we did it like this in the first place. Maybe some more info in microsoft/TypeScript#29729.

Can you add a test that shows the use-case you need it for when it's not extending basetype?

[kripod]

Unfortunately, I don't have the capacity to set up a test right now, sorry.

[forivall]

TypeScript 4.0 no longer needs LiteralUnion (it preserves the literals that are union'd with their base type), so this can probably be closed (and LiteralUnion can eventually be removed) Just double checked in the playground -- maybe not? I need to check their issues. I remember i tested in vscode a few days ago, and it appeared fixed.

[papb]

@forivall I doubt that, since microsoft/TypeScript#29729 is still open...