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  1. JDK
  2. JDK-8013842

Complex generic class with multiple bounds does not compile

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    • Icon: Bug Bug
    • Resolution: Duplicate
    • Icon: P3 P3
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      FULL PRODUCT VERSION :
      java version " 1.7.0_07 "
      Java(TM) SE Runtime Environment (build 1.7.0_07-b10)
      Java HotSpot(TM) 64-Bit Server VM (build 23.3-b01, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      Windows 7: Microsoft Windows [Version 6.1.7601]
      I haven't tested other OS.

      EXTRA RELEVANT SYSTEM CONFIGURATION :
      Tested it directly via command line or with ant 1.8.2 with same result.

      A DESCRIPTION OF THE PROBLEM :
      The source code submitted below does not compile. I get an compilation error. The JDK6 and the eclipse compiler do not complain.

      I have talked to several people about this problem and we are pretty certain, that this is a bug in the compiler. Espcially since changing the Problem class to

      public abstract class ProblemClass<A extends DefaultWrapper<? extends Type1>> {}

      makes the compiler happy (removed the bound I1, see submitted code) although the interface I1 has nothing to do with the method getWrappedObject().

      Unfortunately I need this bound in our code.


      REGRESSION. Last worked in version 6u31

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Compile the submitted code (I have all files in the same package).

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      The code compiles.
      ACTUAL -
      The jdk compiler compiles with 1 error.

      ERROR MESSAGES/STACK TRACES THAT OCCUR :
      src\com\mytest\ProblemClass.java:4: error: types DefaultWrapper<? extends Type1> and AbstractWrapper<? extends Type1> are incompatible; both define getWrappedObject(), but with unrelated return types
      public abstract class ProblemClass<A extends DefaultWrapper<? extends Type1> & I1> {
                                         ^
      1 error

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      public interface I1 {}

      public class BaseType {}

      public class Type1 extends BaseType {}

      public abstract class AbstractWrapper<T extends BaseType> {
      public T getWrappedObject () {
      return null;
      }
      }

      public abstract class DefaultWrapper<T extends Type1> extends AbstractWrapper<T> {}

      public abstract class ProblemClass<A extends DefaultWrapper<? extends Type1> & I1> {}

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

      CUSTOMER SUBMITTED WORKAROUND :
      Override the method in DefaultWrapper and call the super implementation:

      public abstract class DefaultWrapper<T extends Type1> extends AbstractWrapper<T> {

      @Override
      public T getWrappedObject() {
      return super.getWrappedObject();
      }
      }

            Unassigned Unassigned
            webbuggrp Webbug Group
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              Created:
              Updated:
              Resolved: