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
* Determines if the current element can contain an element with the
	 * definition of <code>elementType</code> on context containment.
	 * 
	 * @param module
	 *            the module
	 * @param slotId
	 *            the slot id
	 * @param defn
	 *            the definition of the element
	 * @return <code>true</code> if the slot can contain the an element,
	 *         otherwise <code>false</code>.
	 */
	public final boolean canContain( Module module, int slotId,
			IElementDefn defn )
	{
		assert defn != null;
		boolean retValue = canContainInRom( slotId, defn );
		if ( !retValue )
			return false;
		
		
		if ( isRootIncludedByModule( ) )
			return false;
		if ( !canContainTemplateElement( module, slotId, defn ) )
			return false;
		
		
		if ( isVirtualElement( ) || getExtendsName( ) != null )
			return false;