==== tests/cases/conformance/types/typeParameters/typeArgumentLists/typeParameterAsTypeParameterConstraint2.ts (2 errors) ====
    // using a type parameter as a constraint for a type parameter is invalid
    // these should be errors unless otherwise noted
    
    function foo<T, U extends T>(x: T, y: U): U { return y; } // this is now an error
                    ~~~~~~~~~~~
!!! Constraint of a type parameter cannot reference any type parameter from the same type parameter list.
    
    foo(1, '');
    foo(1, {});
    
    interface NumberVariant extends Number {
        x: number;
    }
    var n: NumberVariant;
    var r3 = foo(1, n);
    
    function foo2<T, U extends { length: T }>(x: T, y: U) { return y; } // this is now an error
                     ~~~~~~~~~~~~~~~~~~~~~~~
!!! Constraint of a type parameter cannot reference any type parameter from the same type parameter list.
    foo2(1, { length: '' });
    foo2(1, { length: {} });
    foo2([], ['']);