According to 5.2 (assignment conversions) the second shouldn't be allowed, as it would be a widening reference conversion followed by an unboxing conversion, which isn't among the allowed conversions. However, I believe that is a bug in the JLS. (One could infer that T must be Integer, as Integer is final, but the type rules don't take advantage of final). A widening reference conversion followed by unboxing isn't listed among the conversions allowed in the corrections in http://java.sun.com/docs/books/jls/jls-proposed-changes.html . Perhaps Alex will get it fixed in the next round.

-Neal

On 5/1/07, ... wrote:
I'm curious about this case:
        
        class A<T extends Integer> {
                     T x = (T)37; // javac gives error
                     int i = (int)x; // javac gives no error
        }
        
        javac gives an error on the first case but not the second. The JLS says
        in 5.5:
        
           A value of a primitive type can be cast to a reference type by
        boxing conversion (§5.1.7).
           A value of a reference type can be cast to a primitive type by
        unboxing conversion (§5.1.8).
        
        It's not clear whether that means one of those conversions plus
        something else.
        If I read it as only boxing or unboxing, the error on the first case
        makes sense.
        But then I would also expect an error on the second case.
        
        Which way is right? Is there a javac bug here on one of these cases?