Lower priority implicits?

gistfile1.scala

scala> :paste
// Entering paste mode (ctrl-D to finish)

class T[+A, +B]
trait LowerPriorityImplicits {
  case object No extends T[Nothing, Nothing]
  implicit val im = No
}
object T extends LowerPriorityImplicits {
  implicit def toT[A, B](implicit ev: A =:= B) = new T[A, B]
}

// Exiting paste mode, now interpreting.

defined class T
defined trait LowerPriorityImplicits
defined module T

scala> implicitly[T[Int, Boolean]]
<console>:12: error: ambiguous implicit values:
 both value im in trait LowerPriorityImplicits of type => T.No.type
 and method toT in object T of type [A, B](implicit ev: =:=[A,B])T[A,B]
 match expected type T[Int,Boolean]
              implicitly[T[Int, Boolean]]
                        ^