[ JDK VERSION : 1.7.0_45 ]

When you rename a variable it is allowed to hide a variable with a larger
scope.
This is not desirable as it can introduce some WERY hard to track errors.

Example;
class Test {
  InputStream input

  Test() {
    InputStream in;
    input=GlobalConnectionBoxHandler.getInputStream();
    in=null;
  }
}

If you in this case (only an example) rename the "in" to "input" it would
destroy the content of "input".

As there is not even a warning I do consider this a BUG rather than an
ENHANCEMENT.