diff --git a/util/collection/HList.scala b/util/collection/HList.scala
index b36f68955..a475c1194 100644
--- a/util/collection/HList.scala
+++ b/util/collection/HList.scala
@@ -1,22 +1,28 @@
+/* sbt -- Simple Build Tool
+ * Copyright 2010 Mark Harrah
+ */
 package sbt
 
 import Types._
 
 sealed trait HList
 {
+	type ToM[M[_]] <: MList[M]
 	type Up <: MList[Id]
 	def up: Up
 }
 sealed trait HNil extends HList
 {
-	type Up = MNil[Id]
+	type ToM[M[_]] = MNil
+	type Up = MNil
 	def up = MNil
 	def :+: [G](g: G): G :+: HNil = HCons(g, this)
 }
 object HNil extends HNil
 final case class HCons[H, T <: HList](head : H, tail : T) extends HList
 {
-	type Up = MCons[H, T#Up, Id]
-	def up = MCons[H,T#Up, Id](head, tail.up)
+	type ToM[M[_]] = MCons[H, tail.ToM[M], M]
+	type Up = MCons[H, tail.Up, Id]
+	def up = MCons[H,tail.Up, Id](head, tail.up)
 	def :+: [G](g: G): G :+: H :+: T = HCons(g, this)
 }
\ No newline at end of file
diff --git a/util/collection/MList.scala b/util/collection/MList.scala
index 981056823..58d2724c3 100644
--- a/util/collection/MList.scala
+++ b/util/collection/MList.scala
@@ -1,42 +1,33 @@
+/* sbt -- Simple Build Tool
+ * Copyright 2010 Mark Harrah
+ */
 package sbt
 
 import Types._
 
-sealed trait MList[M[_]]
+sealed trait MList[+M[_]]
 {
 	type Map[N[_]] <: MList[N]
 	def map[N[_]](f: M ~> N): Map[N]
 
-	type Down <: HList
-	def down: Down
-
 	def toList: List[M[_]]
 }
-final case class MCons[H, T <: MList[M], M[_]](head: M[H], tail: T) extends MList[M]
+final case class MCons[H, +T <: MList[M], +M[_]](head: M[H], tail: T) extends MList[M]
 {
-	type Down = M[H] :+: T#Down
-	def down = HCons(head, tail.down)
-
-	type Map[N[_]] = MCons[H, T#Map[N], N]
+	type Map[N[_]] = MCons[H, tail.Map[N], N]
 	def map[N[_]](f: M ~> N) = MCons( f(head), tail.map(f) )
 
-	def :^: [G](g: M[G]): MCons[G, MCons[H, T, M], M] = MCons(g, this)
+	def :^: [N[X] >: M[X], G](g: N[G]): MCons[G, MCons[H, T, N], N] = MCons(g, this)
 
 	def toList = head :: tail.toList
 }
-sealed class MNil[M[_]] extends MList[M]
+sealed class MNil extends MList[Nothing]
 {
-	type Down = HNil
-	def down = HNil
-	
-	type Map[N[_]] = MNil[N]
-	def map[N[_]](f: M ~> N): MNil[N] = new MNil[N]
+	type Map[N[_]] = MNil
+	def map[N[_]](f: Nothing ~> N) = MNil
 
-	def :^: [H](h: M[H]): MCons[H, MNil[M], M] = MCons(h, this)
+	def :^: [M[_], H](h: M[H]): MCons[H, MNil, M] = MCons(h, this)
 
 	def toList = Nil
 }
-object MNil extends MNil[Id]
-{
-	implicit def apply[N[_]]: MNil[N] = new MNil[N]
-}
\ No newline at end of file
+object MNil extends MNil
diff --git a/util/collection/TypeFunctions.scala b/util/collection/TypeFunctions.scala
index 9a6d96b14..95fb8ae9e 100644
--- a/util/collection/TypeFunctions.scala
+++ b/util/collection/TypeFunctions.scala
@@ -1,3 +1,6 @@
+/* sbt -- Simple Build Tool
+ * Copyright 2010 Mark Harrah
+ */
 package sbt
 
 trait TypeFunctions
@@ -7,11 +10,11 @@ trait TypeFunctions
 	trait P1of2[M[_,_], A] { type Apply[B] = M[A,B] }
 	trait Down[M[_]] { type Apply[B] = Id[M[B]] }
 
-	trait ~>[A[_], B[_]]
+	trait ~>[-A[_], +B[_]]
 	{
 		def apply[T](a: A[T]): B[T]
 	}
 	def Id: Id ~> Id =
-		new ~>[Id, Id] { def apply[T](a: T): T = a }
+		new (Id ~> Id) { def apply[T](a: T): T = a }
 }
 object TypeFunctions extends TypeFunctions
\ No newline at end of file
diff --git a/util/collection/Types.scala b/util/collection/Types.scala
index 40987e257..de468216d 100644
--- a/util/collection/Types.scala
+++ b/util/collection/Types.scala
@@ -1,3 +1,6 @@
+/* sbt -- Simple Build Tool
+ * Copyright 2010 Mark Harrah
+ */
 package sbt
 
 object Types extends TypeFunctions