Uploaded image for project: 'JDK'
  1. JDK
  2. JDK-6450290

Capture of nested wildcards causes type error

    Details

    • Subcomponent:
    • Resolved In Build:
      b27
    • CPU:
      x86
    • OS:
      linux
    • Verification:
      Not verified

      Description

      FULL PRODUCT VERSION :
      java version "1.5.0_07"
      Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_07-b03)
      Java HotSpot(TM) Client VM (build 1.5.0_07-b03, mixed mode, sharing)


      A DESCRIPTION OF THE PROBLEM :
      In the attached code the capture of ? extends Box<?> is not treated right, allowing you to put a Box<B> in a Box<Box<A>>.
      The code compiles without warnings, has no casts, but throws a ClassCastException.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile (and run) the code

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      An error from the compiler
      ACTUAL -
      Incorrect code compiles, and throws a ClassCastException

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      Exception in thread "main" java.lang.ClassCastException: B
              at CaptureBug6.main(CaptureBug6.java:9)

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      // this code compiles without warnings, has no casts,
      // but throws a ClassCastException
      public class CaptureBug6 {
      public static void main(String[] args) {
      Box<Box<A,A >,Box<A,A>> a = new Box<Box<A,A>,Box<A,A>>(new Box<A,A>(new
      A()));
      Box<?, ?> b = a;
      b.value.same = new Box<B,B>(new B());
      A c = a.value.same.value;
      }
      }

      class Box<X extends Box<?,?>, T extends X> {
      Box (T v) {
      value = v;
      }

      Box () {}

      T value;
      Box<X, T> same;

      }

      class A extends Box<A,A> {}
      class B extends Box<B,B> {}


      ---------- END SOURCE ----------

        Attachments

          Issue Links

            Activity

              People

              • Assignee:
                mcimadamore Maurizio Cimadamore
                Reporter:
                ndcosta Nelson Dcosta (Inactive)
              • Votes:
                0 Vote for this issue
                Watchers:
                0 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved:
                  Imported:
                  Indexed: