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
ExpressionCompiler expressionCompiler = new ExpressionCompiler( );
				CompiledExpression expr = expressionCompiler.compile( text,
						aggrReg,
						context );
				return flattenFilterExpression( expr );
			}
			finally
			{
				Context.exit( );
			}
		}
		else if ( expression instanceof IConditionalExpression )
		{
			IScriptExpression expr = ( (IConditionalExpression) expression ).getExpression( );
			IScriptExpression oprand1 = ( (IConditionalExpression) expression ).getOperand1( );
			IScriptExpression oprand2 = ( (IConditionalExpression) expression ).getOperand2( );
			return isValidExpressionInQueryFilter( expr )
					&& isValidExpressionInQueryFilter( oprand1 )
					&& isValidExpressionInQueryFilter( oprand2 );
		}
		return true;
	}
	
	/**
	 * 
	 * @param expr
	 * @return
	 */
	private static String getExprText( IScriptExpression expr )
	{