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  1. JDK
  2. JDK-7030781

problem with multiple interface inheritance using bounded type parameters

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P4
    • Resolution: Not an Issue
    • Affects Version/s: 7
    • Fix Version/s: None
    • Component/s: tools
    • Labels:
    • Subcomponent:
    • CPU:
      x86
    • OS:
      linux

      Description

      FULL PRODUCT VERSION :
      /opt/jdk1.7.0/bin/javac -version
      javac 1.7.0-ea

      Build b134
      Error occurs on 32bit and 64 Linux systems

      ADDITIONAL OS VERSION INFORMATION :
      Linux nodeXYZ 2.6.32-30-generic #59-Ubuntu SMP Tue Mar 1 21:30:21 UTC 2011 i686 GNU/Linux
      Linux nodeXYY 2.6.32-22-generic #36-Ubuntu SMP Thu Jun 3 19:31:57 UTC 2010 x86_64 GNU/Linux

      A DESCRIPTION OF THE PROBLEM :
      In java 6 problems were reported with inheritance of multiple interfaces, e. g.
      http://bugs.sun.com/view_bug.do;jsessionid=38b12cbe58b2634d7bb6dabb8a42?bug_id=6709429
      http://bugs.sun.com/view_bug.do?bug_id=6908259

      This problems were solved in Java 7. However, the problem still exists if bounded type parameters are used. The compilation of a methods using bounded type parameters inheriting from two interfaces fails. For details see source code below.

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      try to compile the source reported below using java 7 (e.g. b134)

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      successful compilation
      ACTUAL -
      compilation fails

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      /opt/jdk1.7.0/bin/javac someClass.java
      someClass.java:19: types B and A are incompatible; both define x(), but with unrelated return types
          public static <M extends A & B> void somePubStatic(M mx)
                         ^
      1 error
      make: [covar] Error 1 (ignored)


      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      public class someClass {

          interface Top {
              Top x();
          }

          interface A extends Top {
              A x();
          }

          interface B extends Top {
              B x();
          }

          // caused a compiler error in Java 6,
          // but was fixed in Java 7
          interface AB extends A, B {
              AB x();
          }

          // causes compiler error in Java 7
          public static <M extends A & B> void somePubStatic(M mx)
          {
          }
      }

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

      CUSTOMER SUBMITTED WORKAROUND :
        Interestingly, the above code compiles successfully in Eclipse.

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              • Assignee:
                mcimadamore Maurizio Cimadamore
                Reporter:
                webbuggrp Webbug Group
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                • Created:
                  Updated:
                  Resolved:
                  Imported:
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