anchor.diff:    Expect.isTrue(set1exp is Set<int>);
   
     var set1 = <int>{for (var i = 1; i < 10; i += 3) i};
  -  // set1exp {1, 4, 7}
     Expect.isTrue(set1 is Set<int>);
     Expect.setEquals(set1exp, set1);
   
  
positive.code:   }
    Expect.isTrue(set3exp is Set<num>);
  
    var set3 = <num>{for (var i = 1.1; i < 10; i += 5) i,
        for (var i = 2; i < 6; i++) i + 3};
    // set2exp {3.1, 8.1, 5, 6, 7, 8}
    Expect.isTrue(set3 is Set<num>);
    Expect.setEquals(set3exp, set3);
  
  
negative.code:   Expect.isTrue(set2exp is Set<double>);
  
    var set2 = <double>{for (var i = 1.1; i < 10; i += 5) i + 2};
    Expect.isTrue(set2 is Set<double>);
    Expect.setEquals(set2exp, set2);
  
  