frog:~/workspaces/test/Generic11 $ ls -la
total 10
drwxr-xr-x 2 gafter 512 Feb 4 15:25 .
drwxr-xr-x 115 gafter 3072 Feb 4 14:48 ..
-rw-r--r-- 1 gafter 49 Feb 4 14:52 MyColor.java
-rw-r--r-- 1 gafter 82 Feb 4 14:53 MyComparable.java
-rw-r--r-- 1 gafter 145 Feb 4 15:25 MyEnum.java
frog:~/workspaces/test/Generic11 $ cat -n MyComparable.java
     1 interface MyComparable<T extends MyComparable<T>> {
     2 int compareTo(T other);
     3 }
frog:~/workspaces/test/Generic11 $ cat -n MyEnum.java
     1 class MyEnum<E extends MyEnum<E>> implements MyComparable<E> {
     2 // abstract void f();
     3
     4 public int compareTo(E other) {
     5 return 0;
     6 }
     7 }
frog:~/workspaces/test/Generic11 $ cat -n MyColor.java
     1 class MyColor extends MyEnum {
     2 void f() {}
     3 }
frog:~/workspaces/test/Generic11 $ newjavac -gj *.java
frog:~/workspaces/test/Generic11 $ # now we make MyEnum.java abstract...
frog:~/workspaces/test/Generic11 $ cat -n MyEnum.java
     1 abstract class MyEnum<E extends MyEnum<E>> implements MyComparable<E> {
     2 // abstract void f();
     3
     4 public int compareTo(E other) {
     5 return 0;
     6 }
     7 }
frog:~/workspaces/test/Generic11 $ newjavac -gj *.java
MyColor.java:1: MyColor should be declared abstract; it does not define compareTo(MyComparable) in MyComparable
class MyColor extends MyEnum {
^
1 error
frog:~/workspaces/test/Generic11 $

This problem is also seen when MyEnum is compiled without -gj.