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