FULL PRODUCT VERSION :
javac 1.6.0-beta2

java version "1.6.0-beta2"
Java(TM) SE Runtime Environment (build 1.6.0-beta2-b86)
Java HotSpot(TM) Client VM (build 1.6.0-beta2-b86, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]


A DESCRIPTION OF THE PROBLEM :
The testcase included with this report yields an error when compiled.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Simply compile the source with javac.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expected that Integer would have been correctly inferred as the type for the NaturallySortedCollection returned by empty(), as it is-a Comparable<Integer>, which qualifies as a Comparable<? super Integer>.

ACTUAL -
Compile error shown below.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
C:\java\jaggregate-trunk\example-src\foo\InferenceExample.java:12: incompatible types; no instance(s) of type variable(s) T exist so that foo.NaturallySortedCollection<T> conforms to foo.NaturallySortedCollection<java.lang.Integer>
    found : <T>foo.NaturallySortedCollection<T>
    required: foo.NaturallySortedCollection<java.lang.Integer>
    final NaturallySortedCollection<Integer> digits = empty();
                                                                                                     ^

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package foo;

import static foo.NaturallySortedCollection.empty;

class NaturallySortedCollection<E extends Comparable<? super E>> {
    static <T extends Comparable<? super T>> NaturallySortedCollection<T> empty() {
        return new NaturallySortedCollection<T>();
    }
}
class InferenceExample {
    public static void main( final String[] args ) {
        final NaturallySortedCollection<Integer> digits = empty();
    }
}

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

CUSTOMER SUBMITTED WORKAROUND :
Provide an explicit type argument of <Integer> to the invocation of empty().