==== tests/cases/compiler/genericsWithDuplicateTypeParameters1.ts (10 errors) ====
    function f<x, x>() { }
                  ~
!!! Duplicate identifier 'x'.
    function f2<X, X>(a: X, b: X): X { return null; }
                   ~
!!! Duplicate identifier 'X'.
    class C<X, X> {
               ~
!!! Duplicate identifier 'X'.
        public f<x, x>() {}
                    ~
!!! Duplicate identifier 'x'.
        public f2<X, X>(a: X, b: X): X { return null; }
                     ~
!!! Duplicate identifier 'X'.
    }
    
    interface I<X, X> {
                   ~
!!! Duplicate identifier 'X'.
        f<X, X>();
             ~
!!! Duplicate identifier 'X'.
        f2<X, X>(a: X, b: X): X;
              ~
!!! Duplicate identifier 'X'.
    }
    
    var m = {
        a: function f<X, X>() {},
                         ~
!!! Duplicate identifier 'X'.
        b: function f2<X, X>(a: X, b: X): X { return null; }
                          ~
!!! Duplicate identifier 'X'.
    }