anchor.diff:  type private PatriciaHashMap<'Key, [<EqualityConditionalOn; ComparisonConditionalOn>] 'T when 'Key : equality> =
       | Empty
       // Key-HashCode * Value
  -    | Lf of uint32 * NonEmptyAssociationList<'Key, 'T>
  +    | Lf of uint32 * ListMap<'Key, 'T>
       // Prefix * Mask * Left-Child * Right-Child
       | Br of uint32 * uint32 * PatriciaHashMap<'Key, 'T> * PatriciaHashMap<'Key, 'T>
   
  
positive.code:             false
          | Lf (j, listMap) ->
              j = keyHash
              && NonEmptyAssociationList.ContainsKey (key, listMap)
          | Br (_, m, t0, t1) ->
              PatriciaHashMap.ContainsKey (
                  keyHash, key, (if zeroBit (keyHash, m) then t0 else t1))
  
negative.code:         | Br (p, m, s0, s1), Lf (k, y) ->
              if matchPrefix (k, p, m) then
                  if zeroBit (k, m) then
                      match PatriciaHashMap.Remove (k, s0) with
                      | Empty -> s1
                      | left ->
                          Br (p, m, left, s1)
                  else
                      match PatriciaHashMap.Remove (k, s1) with
                      | Empty -> s0
                      | right ->
                          Br (p, m, s0, right)
  