Bug 176107 row.__rownum cannot be directly used as group key
Create a table that bind it to a data set. Insert a group. For the Group On field, click on the "..." button to edit the expression, and select from "Availble Column Bindings" | "Table" | "RowNum". This creates a Group On Expression "row.__rownum". The resulting report design cannot be run. It produces error: Column binding "row.__rownum" does not exist. To workaround this, one must create another binding on the table and set its expression to "row.__rownum", then use the new binding as group key. This should not have been necessary. The "__rownum" binding should be implicitly available in all contexts that have a data set. E.g., it should be usable directly as group key, sort key, and in conditional format expressions, etc. Attached is a sample report that produces the error.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ExpressionCompilerUtil.java
if( expr!= null )
			return expr.getText( );
		return null;
	}
	
	/**
	 * 
	 * @param expression
	 * @param exprManager
	 * @return
	 */
	private static boolean compile( String expression, ExprManager exprManager )
	{
		Context context = Context.enter( );
		
		AggregateRegistry aggrReg = new AggregateRegistry( ) {
			public int register( AggregateExpression aggregationExpr )
			{
				return -1;
			}
		};
		try
		{
			ExpressionCompiler expressionCompiler = new ExpressionCompiler( );
			CompiledExpression expr = expressionCompiler.compile( expression,
					aggrReg,
					context );
			return flattenExpression( expr, exprManager );
		}
		finally