anchor.diff:                              | None -> None
                               | Some gfd -> callGenericFormatter self gfd.ImplKind t None |> Some
                       else None
  +
  +                // if that fails, resolve F# core types
   
                   let result =
                       match result with
  
positive.code:                             mkFuncFormatter memberInfoFormatter t |> Some
                          else None
  
  
                  cont result)
  
  
  
negative.code: 
              YParametric initial (fun (self : Type -> Formatter option cell) cont t ->
                  // cache resolution
                  match globalCache.TryFind t.AssemblyQualifiedName with
                  | Some r -> cont r
                  | None ->
  
                  // formatter not in cache, go ahead with resolution
                  // for starters, look for known generic types
  
                  let result =
                      if t.IsGenericType then
  