$ cat -n A.java
     1 interface A {
     2 <D> D clone(D obj);
     3 }
$ cat -n B.java
     1 public abstract class B implements A {
     2 public void foo() { // a function
     3 }
     4 }
$ newjavac -gj A.java
$ newjavac -gj B.java
B.java:1: cannot resolve symbol
symbol : class D
location: class B
public abstract class B implements A {
                ^
1 error
$