typescript-generics-clarity.ts

type ExtractValuesRecusrively<T> = T extends FormState<infer U>
  ? { [K in keyof U]: ExtractValuesRecusrively<U[K]> }
  : T extends FieldState<infer V>
  ? V
  : never;

// vs

type ExtractValuesRecusrively<State> = State extends FormState<infer InnerForm>
  ? { [FieldKey in keyof InnerForm]: ExtractValuesRecusrively<InnerForm[FieldKey]> }
  : State extends FieldState<infer FieldType>
  ? FieldType
  : never;