Creating a reverse collection on a transversable
===

I want to just reverse the items in this collection, so I decided to require that it be part of `Transversable`, and any of the subtypes for it, and have it return a Transversable, but I think I may need to use a variance on that also, but, at the moment I get a compiler error, using Scala 2.10.0-M5.

    trait Polynomials {
    	def coefficients[+A <: Traversable[T]](x:A):Traversable[A] =  x.foldLeft(Traversable[A]())((b,a) => a :: b)

}

These are the errors I am getting, and I am not certain what I did wrong.

Description	Resource	Path	Location	Type
']' expected but identifier found.	Polynomials.scala	line 4	Scala Problem
'=' expected but ']' found.	Polynomials.scala	line 4	Scala Problem
illegal start of simple expression	Polynomials.scala	line 5	Scala Problem
