constantOverloadFunction.ts(11,5): error TS2322: Type 'null' is not assignable to type 'Base'.


==== constantOverloadFunction.ts (1 errors) ====
    class Base { foo() { } }
    class Derived1 extends Base { bar() { } }
    class Derived2 extends Base { baz() { } }
    class Derived3 extends Base { biz() { } }
    
    function foo(tagName: 'canvas'): Derived1;
    function foo(tagName:  'div'): Derived2;
    function foo(tagName: 'span'): Derived3;
    function foo(tagName: string): Base;
    function foo(tagName: any): Base {
        return null;
        ~~~~~~
!!! error TS2322: Type 'null' is not assignable to type 'Base'.
    }
    