Aladdin - Scala Bugtracking
[#349] project: compiler priority: medium category: feature
submitter assigned to status date submitted
Burak Martin won't fix 2004-07-08 14:44:09.0
subject inheritance of virtual types
code 
trait A {
  type foo <: Foo;
  abstract class Foo;
}

trait B extends A {
  type foo = Foo;
  case class Bar(i:Int) extends Foo;
}
class AFun( a:A ) {
  val myA = a;
  val x = new scala.collection.mutable.HashSet[myA.foo];
}
class BFun( b:B ) extends AFun( b ) {
  val myB  = b;
  x += myB.Bar( 2 );
}
what happened 
/tmp> scalac foo.scala
foo.scala:24: type mismatch;
 found   : BFun.this.myB.Bar
 required: BFun.this.myA.foo
  x += myB.Bar( 2 );
              ^
one error found
what expected given myB.Bar <: myB.Foo which is actually foo, silent run
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Changes of this bug report
Burak  edited on  2004-07-08 19:12:05.0
this is not a bug. With Matthias help, I realized that this was the correct thing to do: 
abstract class AFun {
  val my:A;
  val x = new scala.collection.mutable.HashSet[my.foo];
}
abstract class BFun extends AFun {
  val my:B;
  x += my.Bar( 2 );
}
works like a charm now.
Burak  edited on  2004-07-08 19:12:46.0