Scala: abstract types in class parameters

Question

Simple enough, is there a way to marry constructor arguments and abstract types? For example, something that I would like to do

class A(t: Seq[T]) { type T } 

Answer 1

Class members are not in the scope of the constructor parameter description.

It is as close as possible:

 scala> trait T { type T; val a: T } defined trait T scala> def A[X](x: X) = new T { type T = X; val a = x } A: [X](x: X)Object with T{type T = X} scala> A[Int](0) res0: Object with T{type T = Int} = $anon$1@3bd29ee4 scala> A[String](0) <console>:10: error: type mismatch; found : Int(0) required: String A[String](0) ^ scala> class AA[X](val a: X) extends T { type T = X } defined class AA scala> new AA[Int](0) res5: AA[Int] = AA@1b3d4787 scala> new AA[String](0) <console>:10: error: type mismatch; found  : Int(0) required: String      new AA[String](0)              ^ 

Answer 2

Does this not suit your needs?

 class A[T](ts: Seq[T])