Scala example source code file (t2173.scala)

This example Scala source code file (t2173.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

a, a, null, null, o, r, r, x, x

The Scala t2173.scala source code

class A[+U >: Null] {
  type R[+X >: Null] = X
  type O[+X] = A[R[X]]
}

// with the following error:
// 
// type arguments [A.this.R[X]] do not conform to class A's type parameter bounds [+U >: Null]
// 
// However, because type R[+X>:Null] is identical to X, it should carry X bounds and R[X] lower bound should be known to be X's lower bound, i.e. Null.
// 
// The same problem occurs with upper bounds.