crash: java.lang.NullPointerException at com.sun.tools.javac.comp.Check.checkCompatibleConcretes(Che

FULL PRODUCT VERSION :
java version "1.5.0_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_01-b08)
Java HotSpot(TM) Client VM (build 1.5.0_01-b08, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
MS Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
Javac crashes in compiling the test code below.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a file Test.java with the source code below. Then run javac Test.java.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
compiled classes
ACTUAL -
javac crash

ERROR MESSAGES/STACK TRACES THAT OCCUR :
An exception has occurred in the compiler (1.5.0_01). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
        at com.sun.tools.javac.comp.Check.checkCompatibleConcretes(Check.java:1141)
        at com.sun.tools.javac.comp.Check.checkCompatibleSupertypes(Check.java:1495)
        at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:2451)
        at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:2406)
        at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:2355)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:444)
        at com.sun.tools.javac.main.Main.compile(Main.java:592)
        at com.sun.tools.javac.main.Main.compile(Main.java:544)
        at com.sun.tools.javac.Main.compile(Main.java:67)
        at com.sun.tools.javac.Main.main(Main.java:52)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
interface Ac<S extends St<S,A>,A extends Ac<S,A>> { };

interface St<S extends St<S,A>,A extends Ac<S,A>> { };

abstract class CSS<X, Y> implements St<CSS<X, Y>, CSN<X, Y>> {};

final class CSN<X, Y> extends CSS<X, Y> implements Ac<CSS<X, Y>, CSN<X, Y>> {};
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
If class CSN is defined in the file BEFORE class CSS, then the program compiles.
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