Possible GWT compiler/j.l.String bug

compiled onModuleLoad.js

function init(){
  var runtimeValue, test, matchObj;
  !!$stats && onModuleStart('com.google.gwt.user.client.UserAgentAsserter');
  runtimeValue = $getRuntimeValue();
  $equals('gecko1_8', runtimeValue) || ($wnd.alert('ERROR: Possible problem with your *.gwt.xml module file.\nThe compile time user.agent value (gecko1_8) does not match the runtime user.agent value (' + runtimeValue + '). Expect more errors.\n') , undefined);
  !!$stats && onModuleStart('com.google.gwt.user.client.DocumentModeAsserter');
  $onModuleLoad_0();
  !!$stats && onModuleStart('com.google.gwt.logging.client.LogConfiguration');
  $onModuleLoad($clinit_LogConfiguration());
  !!$stats && onModuleStart('com.example.client.Test');
  test = $wnd.prompt('value?', '12');
  alert_0((matchObj = (new RegExp('([0-9]|[0-5][0-9])')).exec(test) , matchObj == null?false:test == matchObj[0]) + '');
  alert_0($test(new RegExp('([0-9]|[0-5][0-9])'), test) + ''); 
} 
function $test(this$static, input){
  return this$static.test(input);
} 

Test.java

package com.example.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.regexp.shared.RegExp;
import com.google.gwt.user.client.Window;

public class Test implements EntryPoint {
  private static final String REGEX = "([0-9]|[0-5][0-9])"; 

  @Override
  public void onModuleLoad() {
    String test = Window.prompt("value?", "12");
    Window.alert(test.matches(REGEX) + "");
    Window.alert(RegExp.compile(REGEX).test(test) + "");
    
  }
}