==== tests/cases/conformance/classes/classDeclarations/classHeritageSpecification/classIsSubtypeOfBaseType.ts (1 errors) ====
    class Base<T> {
        foo: T;
    }
    
    class Derived extends Base<{ bar: string; }> {
        foo: {
            bar: string; baz: number; // ok
        }
    }
    
    class Derived2 extends Base<{ bar: string; }> {
          ~~~~~~~~
!!! Class 'Derived2' incorrectly extends base class 'Base<{ bar: string; }>':
!!!   Types of property 'foo' are incompatible:
!!!     Type '{ bar?: string; }' is not assignable to type '{ bar: string; }':
!!!       Required property 'bar' cannot be reimplemented with optional property in '{ bar?: string; }'.
        foo: {
            bar?: string; // error
        }
    }