Bug 153506 Strange error message when group key refers to bad binding column name
Run attached report design. The following error is shown: Group key "groupkey" in group 1 cannot depend on column bindings defined in the group lower than itself. This is a strange error. Since the actual problem is that the table's binding column "groupkey" is defined to refer to another existing binding: row["bad"]. EXPECTED BEHAVIOR: The error message should clearly indicate that a non-existing binding is the cause of the failure.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
{
	private ExprManager exprManager;
	
	/**
	 * No external instance
	 */
	private ExprManagerUtil( )
	{
	}
	
	/**
	 *	This method tests whether column bindings in ExprManager is valid or not.
	 * 
	 * @param exprManager
	 * @return
	 * @throws DataException
	 */
	public static void validateColumnBinding( ExprManager exprManager )