Incorrect types and missing suggestions when using object index signature

[vladshcherbin]

When using object index signature, known properties get | null type and ref.key suggestions are missing. Without index signature everything is working correctly.

Example with correct ref.key suggestions and correct brand slug field type:

https://kyse.link/?p=s&i=MmozcfIdl4l3HrV97ncr

Same example without ref.key suggestions and with incorrect brand slug field type (it can't be null):

https://kyse.link/?p=s&i=PlNhdkgf4RggHGJnuqVX

kysely 0.27.2

related zod issue - #850

[koskimas]

I don't think it's possible to fix that. Just try doing this

type X = keyof Brand
const x: X = 'slug'

you don't get suggestions for slug even here.

[vladshcherbin]

@koskimas yeah, doesn't work for me too ☹️

What about the brand.slug type from the second example link? It's string | null but from the type it can only be a string. Can this somehow be fixed or it's also not possible?

--- added ---

Managed to get it working when key is not of a string type.
Maybe typescript overrides slug definition when is set as string.

type Brand = {
  slug: string
  [key: number]: string
}

type Key = keyof Brand

const a: Key = 'slug'

Result:

No idea how to fix this sadly ☹️ Seems like microsoft/TypeScript#29729