anchor.diff:          // Preconditions
           checkNonNull "set1" set1
           checkNonNull "set2" set2
  -        
  -        set1.IsSubset set2
  +
  +        IntSet.IsSubset (set1, set2)
   
       /// <summary>
       /// Evaluates to &quot;true&quot; if all elements of the first set are in the second,
  
positive.code:         checkNonNull "set1" set1
          checkNonNull "set2" set2
  
          set1.IsProperSuperset set2
  
      /// Builds a new collection from the given enumerable object.
      [<CompiledName("OfSeq")>]
  
negative.code:         checkNonNull "set1" set1
          checkNonNull "set2" set2
          
          IntSet.IsSubset (set2, set1)
  
      /// <summary>
      /// Evaluates to &quot;true&quot; if all elements of the second set are in the first,
  