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What version of typescript? Do have a reproduction of the type error?

What about using | undefined instead? That animations field is optional and you're making it required, which is not correct.

• typescript version: 5.3.2

Here's a reproducible example: https://gist.github.com/Nearoo/83c5190c075a12c3e2e8464d43eb5763

It will result in:

src/main.ts:32:15 - error TS7053: Element implicitly has an 'any' type because expression of type '"bar"' can't be used to index type 'Record<never, Texture<Resource>[]>'.
  Property 'bar' does not exist on type 'Record<never, Texture<Resource>[]>'.

32 const anims = s.animations['bar']
                 ~~~~~~~~~~~~~~~~~~~

I don't think | undefined would solve the issue, the type will still be never. The issue is that typescript takes the intersection of types for indexed access types, which wasn't always the case. The change was made here.

I understand your concern though. Maybe a better approach would be to change the type of the animations field in Spritesheet here to this?

animations: Record<keyof NonNullable<S['animations']>, Texture[]>;

Yes, the problem is on the Spritesheet class not the data interface.

Alright, update my branch. Would be cool if you could merge, we have a lot of //@ts-ignore over the codebase :)