covariance.scala

class Covariance[+T]

val coAny:Covariance[Any] = new Covariance[String] 
// coAny: Covariance[Any] = Covariance@33a626ac

val coString:Covariance[String] = new Covariance[Any]
/*<console>:8: error: type mismatch;
 found   : Covariance[Any]
 required: Covariance[String]
       val coString:Covariance[String] = new Covariance[Any]
                                         ^
*/
val coString:Covariance[String] = new Covariance[String]
//coString: Covariance[String] = Covariance@7ad7aaf9