Description Richard Hyatt 2005-05-25 17:42:53 EDT

The following test code will generate a "Bound Mismatch" error when compiled 
under 3.1M7:

public class Test
{
	public static <V extends ValueObject, P extends Persistent<V>> P 
createDataObject( V value )
	{
		// create some type of data object given a value object [code 
ommitted]
		return (P)null;
	}
	
	public static void testCreateDataObject()
	{
		ValueObject v = new AValueObject();
		
		Persistent d = createDataObject( v );
	}

	private interface Persistent<V extends ValueObject>
	{
		public V getValueObject();
	}

	private interface ValueObject
	{
	}

	public static class AValueObject implements ValueObject
	{
	}
	
	public static class ADataObject implements Persistent<AValueObject>
	{
		public AValueObject getValueObject()
		{
			return new AValueObject();
		}
	}
}

But when compiled using javac [Sun Java 1.5.03] with -Xlint:all the following 
warning is issued:

Test.java:13: warning: [unchecked] unchecked conversion
found   : <P>P
required: Test.Persistent
                Persistent d = createDataObject( v );
                                               ^
1 warning


Work-around to this problem is to change the above line to:

Persistent<ValueObject> d = createDataObject( v );

but this should not be required since the unchecked base version will assume 
all implementations of Persistent will extend Persistent<ValueObject>.