Date: Tue, 11 Mar 2003 18:37:57 -0500 (EST)
From: C. Scott Ananian
To: jsr14-prototype-comments@sun.com
Subject: Bug in interface inheritance.

The attached gzipped tar file demonstrates a bug in the JSR-14 compiler
version 1.3.  It consists of the following java files:
------- HArrayMethod.java ------
package harpoon.ClassFile;

class HArrayMethod extends HMethodImpl {
    public HArrayMethod() {
    }
}
------- HMember.java ------
package harpoon.ClassFile;

public interface HMember extends java.lang.Comparable<HMember> {
    public abstract int compareTo(HMember o);
}
------- HMethod.java ------
package harpoon.ClassFile;

public interface HMethod extends HMember {
}
------- HMethodImpl.java ------
package harpoon.ClassFile;

abstract class HMethodImpl
  implements HMethod, java.io.Serializable, java.lang.Comparable<HMember> {
  
    public int compareTo(HMember o) { return 0; }
}
-------------------

Note that HArrayMethod implements Comparable<HMember>, but not directly.
When compiled as followes, the compiler gives the following error message
(to reproduce, run 'make' in the directory contained in the included tgz)
----------
cananian@skiffserv:~/JSR14/JSR14BUG1$ make
/home/cananian/jsr14_adding_generics-1_3-ea/scripts/javac -d . -g -source 1.5 *.java
/home/cananian/jsr14_adding_generics-1_3-ea/scripts/javac -d . -g -source 1.5 HArrayMethod.java
HArrayMethod.java:3: harpoon.ClassFile.HArrayMethod is not abstract and
does not override abstract method compareTo(java.lang.Object) in
java.lang.Comparable
class HArrayMethod extends HMethodImpl {
^
1 error
make: *** [bug] Error 1
cananian@skiffserv:~/JSR14/JSR14BUG1$
------------
Note that, in this case, the bug doesn't occur when compiling HArrayMethod
with other files, only when compiling it separately.  However, in the
original use which this testcase was derived from exactly the opposite
occured: the compiler would indicate an error *unless* the file was
compiled separately.  This bug appears to be quite sensitive.

I hope this allows you to find and fix the bug!
 --scott

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                         ( http://cscott.net/ )

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