anchor.diff:                  // add entry with recursion
                   let idx = hashToIndex hkv.H dep
                   let entry = arr.[idx]
  -                let arr = arr.Clone () :?> Vnode<'k, 'v> array
  -                arr.[idx] <- add5 hkv (dep + 1) mdep entry
  +                let arr = cloneArray arr
  +                arr.[idx] <- add hkv earr mdep (dep + 1) entry
                   Multiple arr
   
               | Clash _ ->
  
positive.code: [<RequireQualifiedAccess; CompilationRepresentation (CompilationRepresentationFlags.ModuleSuffix)>]
  module internal Vnode =
  
      let private makeArray () =
          Array.create 32 Nil
  
      let private hashToIndex h dep =
          (h >>> (dep * 5)) &&& 0x1F
  
      let rec private add5 (hkv : Hkv<'k, 'v>) (dep : int) (mdep : int) (node : Vnode<'k, 'v>) : Vnode<'k, 'v> =
          if dep <= mdep then
  
              // handle non-clash cases
  
negative.code:                 let idx = hashToIndex hkv.H dep
                  let idx' = hashToIndex hkv'.H dep
                  if idx <> idx' then
                      let arr = cloneArray earr
                      arr.[idx] <- Singlet hkv
                      arr.[idx'] <- Singlet hkv'
                      Multiple arr
  