type
  NodeKind = enum
    nkInt, nkFloat

  Node = ref NodeObj
  NodeObj = object
    case kind: NodeKind
    of nkInt: intVal: int
    of nkFloat: floatVal: float


let a: Node = Node(kind: nkInt, intVal: 2)
echo a.intVal
a.kind = nkFloat

a.floatVal = 2.0
echo a.floatVal