Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
}
	/**
	 * Checks if this element derives from the given element. The check is true
	 * if this element derives from the target, or if the target is an ancestor
	 * of this element.
	 * 
	 * @param element
	 *            The potential ancestor.
	 * @return True if the given element is an ancestor of this element, false
	 *         otherwise.
	 */
	public boolean isKindOf( DesignElement element )
	{
		DesignElement e = this;
		while ( e != null )
		{
			if ( e == element )
				return true;
			e = e.getExtendsElement( );
		}
		return false;
	}
	/**
	 * Determines if any elements extend this element.
	 * 
	 * @return True if the element is extended, false if not.
	 */
	public boolean hasDerived( )
	{
		return derived != null && derived.size( ) > 0;