[Fedelaus]

I think the unknown example is good but also somewhat confusing, because implicit typing would understand what set of types could be in that array at that moment.

Is there another example someone could give for unknown which isn't handled by implicit typing?

[shadowgovt]

  interface ServerResponse {
    data: unknown;
  }

... this is the most common way I see unknown used. Then when you fetch data from the server, you are reminded by the compiler that you should do some duck-type checking on it to make sure it's shaped correctly (since responses from a server can be any shape; is it a 200 with your data, or did a caching layer vend you an old version of this data structure, or is something catastrophically wrong and you're seeing a 200 where the payload is HTML saying "Set up your apache server," etc.)

BTW, TypeScript has another useful tool for tying the runtime typing and static typing together: type guards.

  function isUserRecord(x: unknown): x is UserRecord {
    return (x as UserRecord).name !== undefined;
  }

This is a boolean function but the type system understands that in codepaths where it returns true, the 'x' argument is known to have the UserRecord type. Great for codifying your type-discernment logic.