RFR: cleanup - removed unneeded casts in jdi

[David Holmes]

Hi Egor,

On 23/12/2017 1:32 AM, Egor Ushakov wrote:
> Hi all,
> 
> could you please review and sponsor this small cleanup removing unneeded 
> casts in jdi LocationImpl and MirrorImpl.
> They were preventing creating custom Location and Mirror implementations 
> used for tests and IDEA debugger impl.
> http://cr.openjdk.java.net/~avu/egor.ushakov/cast_fix/

src/jdk.jdi/share/classes/com/sun/tools/jdi/LocationImpl.java

!     public int compareTo(Location object) {
-        LocationImpl other = (LocationImpl)object;

The existing code is somewhat suspect as the Location interface 
implements Comparable but it does not specify what it means to compare 
two Locations! That's a bug in itself. LocationImpl has decided how to 
compare two LocaltionImp's (but doesn't even check they are in the same 
VirtualMachine!). Can we generalize that to accommodate other Location 
implementations? Your change allows for this to happen, but it will only 
work as expected if the other Location implementations use the same 
comparison basis as LocationImpl - which is unspecified.

src/jdk.jdi/share/classes/com/sun/tools/jdi/MirrorImpl.java

Change looks good. It would also seem that now this change is made that 
this:

   37     protected VirtualMachineImpl vm;
   38
   39     MirrorImpl(VirtualMachine aVm) {
   40         super();
   41
   42         // Yes, its a bit of a hack. But by doing it this
   43         // way, this is the only place we have to change
   44         // typing to substitute a new impl.
   45         vm = (VirtualMachineImpl)aVm;

might reduce to:

   37     protected VirtualMachine vm;
   38
   39     MirrorImpl(VirtualMachine aVm) {
   40         super();
   41         vm = aVm;

if we no longer depend on it being VirtualMachineImpl ... and neither do 
subclasses.

David
-----

> I do not have rights to create JDK bug report directly, please create it 
> if it is needed for the procedure.
> 
> Thanks!
>