let all_same_color cs =
  let mutable d=true
  let (col:Color) = card_color (cs.Head:Card)
  for i in cs do
    let col=card_color i
    if not (col = col) then
      printfn "Black"
      d<-false
    else
      d<-d
    printfn "Val %b" d
  d

let (col:Color) = card_color (cs.Head:Card)

 Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this programpoint to constrain the type of the object. This may allow the lookup to be resolved.