Bug 125420 [Commands] parameters: allow commands to specify return type
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/Command.java
private final void fireNotDefined(final NotDefinedException e) {
		
		if (DEBUG_COMMAND_EXECUTION) {
			Tracing.printTrace("COMMANDS", "execute" + Tracing.SEPARATOR 
					+ "not defined: id=" + getId() + "; exception=" + e); 
		}
		if (executionListeners != null) {
			final Object[] listeners = executionListeners.getListeners();
			for (int i = 0; i < listeners.length; i++) {
				final Object object = listeners[i];
				if (object instanceof IExecutionListenerWithChecks) {
					final IExecutionListenerWithChecks listener = (IExecutionListenerWithChecks) object;
					listener.notDefined(getId(), e);
				}
			}
		}
	}
	/**
	 * Notifies the execution listeners for this command that an attempt to
	 * execute has failed because there is no handler.
	 * 
	 * @param e
	 *            The exception that is about to be thrown; never
	 *            <code>null</code>.
	 * @since 3.2
	 */
	private final void fireNotEnabled(final NotEnabledException e) {
		
		if (DEBUG_COMMAND_EXECUTION) {
			Tracing.printTrace("COMMANDS", "execute" + Tracing.SEPARATOR