code: private void enforceVersionSupported()
      {
          if ( _versionSupported != null )
          {
              int majorSupported = _versionSupported.major();
              int minorSupported = _versionSupported.minor();
  
              if ( majorSupported < 0 )    // no real version support requirement
                  return;
  
              AptControlInterface ci = getControlInterface();
              if ( ci == null )
                  return;
  
              int majorPresent = -1;
              int minorPresent = -1;
              Version ciVersion = ci.getVersion();
              if ( ciVersion != null )
              {
                  majorPresent = ciVersion.major();
                  minorPresent = ciVersion.minor();
  
                  if ( majorSupported >= majorPresent &&
                       (minorSupported < 0 || minorSupported >= minorPresent) )
                  {
                      // Version requirement is satisfied
                      return;
                  }
              }
  
              //
              // Version requirement failed
              //
  
              _ap.printError( _implDecl, "versionsupported.failed", _implDecl.getSimpleName(), majorSupported, minorSupported,
                              majorPresent, minorPresent );
          }
      }
docs: Enforces the VersionRequired annotation for control extensions.