iteratorConcat.ts(9,17): error TS2345: Argument of type 'string' is not assignable to parameter of type 'Iterable<string> & object'.
  Type 'string' is not assignable to type 'object'.


==== iteratorConcat.ts (1 errors) ====
    const concatenated: IteratorObject<number | string, undefined, unknown> = Iterator.concat(
        [1, 2],
        new Set(["a", "b"]),
    );
    
    const empty: IteratorObject<never, undefined, unknown> = Iterator.concat();
    
    // Iterator.concat requires iterable objects; unlike Iterator.from, it does not accept string primitives.
    Iterator.concat("abc");
                    ~~~~~
!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'Iterable<string> & object'.
!!! error TS2345:   Type 'string' is not assignable to type 'object'.
    