function works(arg: unknown): void {
  typeof arg === "object" && !!arg && Object.keys(arg);
}

function fails<T extends unknown>(arg: T): void {
  // No overload matches this call.
  // Overload 1 of 2, '(o: {}): string[]', gave the following error.
  //   Argument of type 'T' is not assignable to parameter of type '{}'.
  //     Type 'unknown' is not assignable to type '{}'.
  // Overload 2 of 2, '(o: object): string[]', gave the following error.
  //   Argument of type 'T' is not assignable to parameter of type 'object'.
  //     Type 'unknown' is not assignable to type 'object'.
  typeof arg === "object" && !!arg && Object.keys(arg);
}