Compilation time affected hugely by type inference

1.scala

sealed trait Nat {
  type Self <: Nat
  type + [_ <: Nat] <: Nat
  type * [_ <: Nat] <: Nat
  type Flip_^ [_ <: Nat] <: Nat
  type ^ [T <: Nat] = T # Flip_^[Self]
  type ++ = Succ[Self]
}

object Nat {
  type _0 = Zero.type
  type _1 = _0 # ++
  type _2 = _1 # ++
  type _3 = _2 # ++
  type _4 = _3 # ++
  type _5 = _4 # ++
  type _6 = _5 # ++
  type _7 = _6 # ++
  type _8 = _7 # ++
  type _9 = _8 # ++
  type _10 = _9 # ++
  println((null:( _2 # ^ [_4] )):( _1 # * [_10] # + [_6] ))
  //println((null:( _2 # ^ [_5] )):( _3 # * [_10] # + [_2] ))
}

final object Zero extends Nat {
  type Self = Zero.type
  type + [X <: Nat] = X
  type * [_ <: Nat] = Nat._0
  type Flip_^ [_ <: Nat] = Nat._1
}

final class Succ[N <: Nat] extends Nat {
  type Self = Succ[N]
  type + [X <: Nat] = Succ[N # + [X]]
  type * [X <: Nat] = (N # * [X]) # + [X]
  type Flip_^ [X <: Nat] = (N # Flip_^ [X]) # * [X]
}