anchor.diff:   */
   
   abstract class Base {
  -  a();
  +  a() {
  +
  +  }
  +  b() {
  +
  +  }
   }
   
  -class S extends Base with A {
  +class S extends Base {
     a() {
  +    print("S.a");
       super.a();
  -    print("S.a");
     }
   }
   
   class A extends Base {
     a() {
       print("A.a");
  +    super.a();
     }
   
     b() {
       print("A.b");
  +    super.b();
  +  }
  +}
  +
  +class A1 extends Base {
  +  a() {
  +    print("A1.a");
  +    super.a();
  +  }
  +
  +  b() {
  +    print("A1.b");
  +    super.b();
  +  }
  +}
  +
  +class A2 extends Base {
  +  a() {
  +    print("A2.a");
  +    super.a();
  +  }
  +
  +  b() {
  +    print("A2.b");
  +    super.b();
     }
   }
   
   class B extends Base {
     a() {
       print("B.a");
  +    super.a();
     }
   
     b() {
       print("B.b");
  +    super.b();
     }
   
     c() {
  
positive.code:   }
  }
  
  class T = B with A, S;
  
  
  testMixins() {
  
negative.code:   t.a();
    t.b();
    t.c();
  }
  
  /**
   *  I/flutter ( 1864): S.a
      I/flutter ( 1864): A.a
      I/flutter ( 1864): A2.a
      I/flutter ( 1864): A1.a
      I/flutter ( 1864): B.a
      I/flutter ( 1864): A.b
      I/flutter ( 1864): A2.b
      I/flutter ( 1864): A1.b
      I/flutter ( 1864): B.b
      I/flutter ( 1864): B.c
   * */