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
return true;
				if ( exprManager.getExpr( columnName )!=null )
				{
					String expression = ( (IScriptExpression) exprManager.getExpr( columnName ) ).getText( );
					return compile( expression, exprManager );
				}
				else
				{
					return false;
				}
			}
			case CompiledExpression.TYPE_SINGLE_AGGREGATE :
			{
				Iterator args = ( (AggregateExpression) expr ).getArguments( )
						.iterator( );
				while ( args.hasNext( ) )
				{
					if ( !flattenExpression( (CompiledExpression) args.next( ),
							exprManager ) )
						return false;
				}
			}
			case CompiledExpression.TYPE_CONSTANT_EXPR :
			case CompiledExpression.TYPE_INVALID_EXPR :
			{
				return true;
			}
		}
		return true;
	}