anchor.diff:    Expect.isTrue(map3exp is Map<double, int>);
   
     var map3 = <double,int>{for (var i = 1; i < 10; i += 5) i + 1.5: i};
  -  // map3exp {2.5: 1, 7.5: 6}
     Expect.isTrue(map3 is Map<double, int>);
  -  Expect.listEquals(map3exp, map3);
  +  Expect.mapEquals(map3exp, map3);
   
     var map4exp = <num, num>{};
     for (var i = 1.1; i < 10; i += 5) {
  
positive.code:   Expect.isTrue(map2exp is Map<int, double>);
  
    var map2 = <int, double>{for (var i = 1; i < 10; i += 5) i: i + .5};
    // map2exp {1: 1.5, 6: 6.5}
    Expect.isTrue(map2 is Map<int, double>);
    Expect.listEquals(map2exp, map2);
  
    var map3exp = <double, int>{};
    for (var i = 1; i < 10; i += 5) {
  
negative.code:   Expect.isTrue(map1exp is Map<int, int>);
  
    var map1 = <int, int>{for (var i = 1; i < 10; i += 3) i: i + 1};
    Expect.isTrue(map1 is Map<int, int>);
    Expect.mapEquals(map1exp, map1);
  
  