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/api/ElementFactory.java
}
		return null;
	}
	/**
	 * Creates an extension element specified by the extension type name.
	 * 
	 * @param elementTypeName
	 *            the element type name
	 * @param name
	 *            the optional element name
	 * 
	 * @return design element, <code>null</code> returned if the extension
	 *         with the given type name is not found
	 */
	private DesignElementHandle newExtensionElement( String elementTypeName,
			String name )
	{
		MetaDataDictionary dd = MetaDataDictionary.getInstance( );
		ExtensionElementDefn extDefn = (ExtensionElementDefn) dd
				.getExtension( elementTypeName );
		if ( extDefn == null )
			return null;
		String extensionPoint = extDefn.getExtensionPoint( );
		if ( PeerExtensionLoader.EXTENSION_POINT
				.equalsIgnoreCase( extensionPoint ) )
			return newExtendedItem( name, elementTypeName );
		return null;
	}
	/**
	 * Creates a new free-form item.