anchor.diff:          
           set1.Intersect set2
   
  +    /// Computes the intersection of a sequence of sets.
  +    [<CompiledName("IntersectMany")>]
  +    let intersectMany sets =
  +        // Preconditions checked by the target method.
  +        IntSet.IntersectMany sets
  +
       /// Returns a new set with the elements of the second set removed from the first.
       [<CompiledName("Difference")>]
       let inline difference (set1 : IntSet) (set2 : IntSet) : IntSet =
  
positive.code:         checkNonNull "set2" set2
  
          set1.Intersect set2
          |> retype
  
      /// Returns a new set with the elements of the second set removed from the first.
  
negative.code:             IntSet (PatriciaSet.OfArray source)
  
      /// Returns a new IntSet made from the given elements.
      static member internal OfSet (source : Set<int>) : IntSet =
          // Preconditions
          checkNonNull "source" source
  
  