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  1. JDK
  2. JDK-7008619

Regression : Generic cast error caused by fix for CR 4916620 in JDK 5

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: P3
    • Resolution: Fixed
    • Affects Version/s: 7
    • Fix Version/s: 6
    • Component/s: tools
    • Labels:
    • Subcomponent:
    • CPU:
      generic
    • OS:
      generic

      Description

      SYNOPSIS
      --------
      Generic cast error caused by fix for CR 4916620

      OPERATING SYSTEM
      ----------------
      All

      FULL JDK VERSION
      ----------------
      1.5.0_07 - Warning, no error.
      1.5.0_08 - _28 - Error, instead of warning.
      JDK 6 - Warning, no error.
      JDK 7 - Warning, no error.

      PROBLEM DESCRIPTION from LICENSEE
      ---------------------------------
      The fix for CR 4916620 leads to a regression in javac. Code that previously compiled with a warning now fails to compile. The problem is limited to 5.0 - the Java 6 javac implementation compiles the code with just a warning, even though 4916620 was also fixed in 6 (perhaps there is some other fix that needs to be ported to 5.0?). JDK 7 throws
      a warning, in

      REPRODUCTION INSTRUCTIONS
      -------------------------
      Attempt to compile the attached testcase with the following command:

         javac -Xlint:unchecked WeakValueHashMap.java

      You will see the following results:

      1.5.0_07 and earlier:
      =====================
      WeakValueHashMap.java:9: warning: [unchecked] unchecked cast
      found : java.lang.ref.Reference<capture of ? extends V>
      required: WeakValueHashMap<K,V>.KeyWeakReference<V>
              KeyWeakReference<V> sr = (KeyWeakReference<V>) this.queue.poll();
                                                                            ^
      1 warning
      ========

      1.5.0_08 and later:
      ===================
      WeakValueHashMap.java:9: inconvertible types
      found : java.lang.ref.Reference<capture of ? extends V>
      required: WeakValueHashMap<K,V>.KeyWeakReference<V>
              KeyWeakReference<V> sr = (KeyWeakReference<V>) this.queue.poll();
                                                                            ^
      1 error
      ========

      Any Java 6:
      ===========
      WeakValueHashMap.java:9: warning: [unchecked] unchecked cast
      found : java.lang.ref.Reference<capture#159 of ? extends V>
      required: WeakValueHashMap<K,V>.KeyWeakReference<V>
              KeyWeakReference<V> sr = (KeyWeakReference<V>) this.queue.poll();
                                                                            ^
      1 warning
      ========

      JDK 7:
      ======
      WeakValueHashMap.java:193: warning: [unchecked] unchecked cast
                      KeyWeakReference<V> sr = (KeyWeakReference<V>) this.queue.poll();
                                                                                    ^
        required: WeakValueHashMap<K,V>.KeyWeakReference<V>
        found: Reference<CAP#1>
        where V,K are type-variables:
          V extends Object declared in class WeakValueHashMap
          K extends Object declared in class WeakValueHashMap
        where CAP#1 is a fresh type-variable:
          CAP#1 extends V from capture of ? extends V
      1 warning
      =========


      TESTCASE
      --------

      Testcase is attached to this bug report.

      Note: To see the warnings with this code you need to comment out the
      annotation below, which suppresses the warnings:
      // @SuppressWarnings("unchecked")



      WORKAROUND
      ----------
      Change this line in the release() method from:

          KeyWeakReference<V> sr = (KeyWeakReference<V>) this.queue.poll();

      to this:

          KeyWeakReference sr = (KeyWeakReference) this.queue.poll();

      But it's not clear what side effects this may have.

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              • Assignee:
                kizune Alexander Zuev
                Reporter:
                dkorbel David Korbel (Inactive)
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                • Created:
                  Updated:
                  Resolved:
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