Seems like a bug, complains about property type

[al6x]

Code

This code won't compile

export type Errors<D> = {
  readonly [K in (keyof D | 'base')]?: string[]
}

class Model<D> {
  getErrors(): Errors<D> {
    return { base: ['some base error'] }
  }
}

Expected behavior:

It should compile without errors

Playground

[al6x]

Impressive, I just added that bug a day ago and you already created a PR with the fix.
Thanks for your work!