anchor.diff:  
       /// OPTIMIZATION: Requires an empty array to use the source of new array clones in order to avoid Array.create.
       let rec add (hkv : Hkv<'k, 'v>) (earr : Vnode<'k, 'v> array) (mdep : int) (dep : int) (node : Vnode<'k, 'v>) : Vnode<'k, 'v> =
  +
  +        // lower than max depth, non-clashing
           if dep < mdep then
   
               // handle non-clash cases
  
positive.code: 
              | Singlet hkv' ->
                  
                  // additional entry; convert Singlet to Multiple
                  let idx = hashToIndex hkv.H dep
                  let idx' = hashToIndex hkv'.H dep
                  if idx <> idx' then
  
negative.code: [<RequireQualifiedAccess; CompilationRepresentation (CompilationRepresentationFlags.ModuleSuffix)>]
  module internal Vnode =
  
      /// OPTIMIZATION: Array.Clone () is not used since it's been profiled to be slower
      let inline cloneArray (arr : Vnode<'k, 'v> array) : Vnode<'k, 'v> array =
          let arr' = Array.zeroCreate 32 // there's an unecessary check against the size here, but that's the only inefficiency
          Array.Copy (arr, 0, arr', 0, 32) // param checks are inefficient, but hopefully there's at least a memcpy underneath...
          arr'
  
      let inline private hashToIndex h dep =
  