anchor.diff:          // Preconditions
           checkNonNull "set" set
   
  -        set.Add (int key)
  +        set.Add (int64 key)
           |> retype
   
       /// Returns a new set with the given element removed.
  
positive.code:     /// The set containing the given element.
      [<CompiledName("Singleton")>]
      let inline singleton (element : int64<'Tag>) : LongTagSet<'Tag> =
          LongSet.Singleton (int element)
          |> retype
  
      /// Returns a new set with an element added to the set.
  
negative.code:         // Preconditions
          checkNonNull "set" set
  
          set.Remove (int64 key)
          |> retype
  
      /// <summary>
  