gcc/testsuite/g++.old-deja/g++.law/typeck4.C

// { dg-do assemble  }
// GROUPS passed typeck
class A {
  public:
    const int &operator[]( int i );
  private:
    int k;
};

const int& A::operator[]( int i )
{
    return k;
}


void ff( A &anA )
{
    int &ani = anA[0];// { dg-error "" } 

    ani = 7;
}