Bug 151959 inappropriate screen operation
steps to reproduce: - create a report - add a grid item (3x3) - switch to Outline view - expand the grid item to see its rows and cells - select the grid item, and drag it into any of its own cell expected behavior: - is it an invalid screen operation? if it is, it should be banned actual behavior: - the grid item was disappeared surprisingly
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* <p>
	 * This class has two intrinsic properties:
	 * <ul>
	 * <li><strong>name </strong>-- The element name. The property value must
	 * be null or a String.
	 * <li><strong>extends </strong>-- The element that this element extends.
	 * Must be a String (for an unresolved name), DesignElement (for a resolved
	 * name) or null. The caller should ensure canExtend of this element is
	 * true.
	 * </ul>
	 * 
	 * @param propName
	 *            The name of the intrinsic property.
	 * @param value
	 *            The value to set for the property.
	 */
	protected void setIntrinsicProperty( String propName, Object value )
	{
		if ( propName.equals( NAME_PROP ) )
		{
			setName( (String) value );
		}
		else
		{
			assert false;
		}
	}
	/**
	 * Sets the value of a property. The value must have already been validated,
	 * and must be of the correct type for the property. The property name must