unused type declaration causes totally unrelated error (Index signatures are incompatible)

Bug Report

🕗 Version & Regression Information

Getting same error on all versions I tried.

⏯ Playground Link

Playground link with relevant code

💻 Code

interface Ref<Prefix extends string> {
  $ref: string;
  prefix: Prefix;
}
   
 
type FFF = { faa: number };

// if you comment this line out the error will disappear
// NOTE THIS TYPE IS NOT USED AT ALL 😱
type KAMIKADZE = { asdasdasd: Record<string, FFF>; }

declare const x: {
  responses: Record<string, number>;
  fff: Record<string, FFF>;
};

// if you comment out first declaration of `KAMIKADZE` and uncomment this one
// THE ERROR WILL disappear 😱
// type KAMIKADZE = { asdasdasd: Record<string, FFF>; }



mustResolveRef({ $ref: "", prefix: "responses" }, x);
//                                            ___^^^___
// Argument of type '{ responses: Record<string, number>; fff: Record<string, FFF>; }' is not assignable to parameter of type 'Record<"responses", Record<string, FFF>>'.
//   Types of property 'responses' are incompatible.
//     Type 'Record<string, number>' is not assignable to type 'Record<string, FFF>'.
//       Index signatures are incompatible.
//         Type 'number' is not assignable to type 'FFF'.


declare function mustResolveRef<T extends string, V>(
  ref: Ref<T>,
  components: Record<T, Record<string, V>>
): V | undefined

🙁 Actual behavior

Actual behavior is super strange. tried to express this in code comments.

🙂 Expected behavior

It's expected that, having some type declaration, that's not used and is not in conflict with anything, to not cause totally unrelated error.

Plus the error itself shouldn't be thrown as if I do this, all works fine:

const y: Pick<typeof x,"responses"> = x
mustResolveRef({ $ref: "", prefix: "responses" }, y);