[Ada] Better error message for aliased formal and atomic actual

2019-12-13  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* sem_res.adb (Resolve_Actuals): Give canonical error for
	illegal case of atomic/volatile parameter also if the formal is
	aliased.

From-SVN: r279364

gcc/ada/ChangeLog

 2019-12-13  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* sem_res.adb (Resolve_Actuals): Give canonical error for
+	illegal case of atomic/volatile parameter also if the formal is
+	aliased.
+
+2019-12-13  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* sem_util.ads (Is_Atomic_Object): Mention relevant RM clauses.
 	* sem_util.adb (Is_Atomic_Object): For an indexed component,
 	only look at the Has_Atomic_Components aspect of the prefix and

gcc/ada/sem_res.adb

@@ -4717,7 +4717,7 @@ package body Sem_Res is
 
             --  Check bad case of atomic/volatile argument (RM C.6(12))
 
-            if Is_By_Reference_Type (Etype (F))
+            if (Is_By_Reference_Type (Etype (F)) or else Is_Aliased (F))
               and then Comes_From_Source (N)
             then
                if Is_Atomic_Object (A)