report warning on empty match

distribution/lib/Standard/Table/0.0.0-dev/src/Internal/Table_Helpers.enso

@@ -6,7 +6,7 @@ import Standard.Base.Data.Ordering.Vector_Lexicographic_Order
 from Standard.Base.Data.Text.Text_Ordering as Text_Ordering_Module import Text_Ordering
 from Standard.Base.Error.Problem_Behavior as Problem_Behavior_Module import Problem_Behavior, Report_Warning
 import Standard.Table.Data.Position
-from Standard.Table.Error as Error_Module import Missing_Input_Columns, Column_Indexes_Out_Of_Range, No_Output_Columns, Duplicate_Column_Selectors, Input_Indices_Already_Matched, Too_Many_Column_Names_Provided, Duplicate_Output_Column_Names, Invalid_Output_Column_Names
+from Standard.Table.Error as Error_Module import Missing_Input_Columns, Column_Indexes_Out_Of_Range, No_Output_Columns, Duplicate_Column_Selectors, Input_Indices_Already_Matched, Too_Many_Column_Names_Provided, Duplicate_Output_Column_Names, Invalid_Output_Column_Names, No_Input_Columns_Selected
 from Standard.Table.Data.Column_Selector as Column_Selector_Module import Column_Selector, By_Name, By_Index, By_Column
 import Standard.Table.Data.Column_Mapping
 import Standard.Table.Internal.Unique_Name_Strategy
@@ -370,6 +370,8 @@ prepare_order_by internal_columns column_selectors on_problems =
             here.select_columns_by_index internal_columns index_selectors problem_builder index_extractor=(_.index)
         Sort_Column_Selector.By_Column column_selectors ->
             here.select_columns_by_column_reference internal_columns column_selectors problem_builder column_extractor=(_.column)
+    if selected_elements.is_empty then
+        problem_builder.report_other_warning No_Input_Columns_Selected
     problem_builder.attach_problems_after on_problems selected_elements
 
 ## PRIVATE