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.tests/test/org/eclipse/birt/data/engine/binding/GroupOnRowTest.java
String metaData = "";
		metaData += formatStr( "ID", expectedLen );
		metaData += formatStr( "_rowPosition", expectedLen );
		metaData += formatStr( "AMOUNT1", expectedLen );
		metaData += formatStr( "AMOUNT2", expectedLen );
		this.testPrintln( metaData );
		while ( ri.next( ) )
		{
			String rowData = "";
			for ( int j = 0; j < bindingNameRow.length; j++ )
			{
				String value = ri.getValue( bindingNameRow[j] ).toString( );
				rowData += formatStr( value, expectedLen );
			}
			this.testPrintln( rowData );
		}
		this.checkOutputFile( );
	}
	
	/**
	 * Test feature of group on row position
	 * 
	 * @throws Exception
	 */
	public void testGroupOnRowPosition( ) throws Exception
	{
		String[] bindingNameGroup = new String[3];
		bindingNameGroup[0] = "GROUP_ID";
		bindingNameGroup[1] = "GROUP_0";
		bindingNameGroup[2] = "GROUP_AMOUNT1";