[Ada] SPARK: minor error message enhancement

2018-09-26  Elisa Barboni  <barboni@adacore.com>

gcc/ada/

	* sem_prag.adb (Check_Refined_Global_Item): Improve error
	message.

From-SVN: r264637

gcc/ada/ChangeLog

+2018-09-26  Elisa Barboni  <barboni@adacore.com>
+
+	* sem_prag.adb (Check_Refined_Global_Item): Improve error
+	message.
+
 2018-09-26  Thomas Quinot  <quinot@adacore.com>
 
 	* sem_ch13.adb (Inherit_Aspects_At_Freeze_Point): For a

gcc/ada/sem_prag.adb

@@ -27730,7 +27730,10 @@ package body Sem_Prag is
                --  it must be an extra (SPARK RM 7.2.4(3)).
 
                else
-                  SPARK_Msg_NE ("extra global item &", Item, Item_Id);
+                  pragma Assert (Present (Global));
+                  Error_Msg_Sloc := Sloc (Global);
+                  SPARK_Msg_NE ("extra global item & does not refine or " &
+                                "repeat any global item #", Item, Item_Id);
                end if;
             end if;
          end Check_Refined_Global_Item;