type FuncType<'a, 'b, 'c> = FuncType of ('b -> 'c)

let dummy<'a> (x:int) = Unchecked.defaultof<int>

let makeFunc (typ:FuncType<'a, 'b, 'c>) =
  let (FuncType f) = typ
  fun (_:'a) -> f

let f2 = makeFunc (FuncType(dummy<int>))