[Ada] Suggest use of First_Valid/Last_Valid on type with static predicate

Attributes First_Valid/Last_Valid can be used on types with static
predicate, instead of First/Last/Range. Include that suggestion in
the corresponding error message.

gcc/ada/

	* sem_util.adb (Bad_Predicated_Subtype_Use): Add continuation
	message.

1 files changed, 25 insertions, 0 deletions

diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
index 1fc2c61..d76b5d9 100644
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -1719,6 +1719,31 @@ package body Sem_Util is
             Error_Msg_FE (Msg, N, Typ);
          end if;
 
+         --  Suggest to use First_Valid/Last_Valid instead of First/Last/Range
+         --  if the predicate is static.
+
+         if not Has_Dynamic_Predicate_Aspect (Typ)
+           and then Has_Static_Predicate (Typ)
+           and then Nkind (N) = N_Attribute_Reference
+         then
+            declare
+               Aname   : constant Name_Id := Attribute_Name (N);
+               Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
+            begin
+               case Attr_Id is
+                  when Attribute_First =>
+                     Error_Msg_F ("\use attribute First_Valid instead", N);
+                  when Attribute_Last =>
+                     Error_Msg_F ("\use attribute Last_Valid instead", N);
+                  when Attribute_Range =>
+                     Error_Msg_F ("\use attributes First_Valid and "
+                                  & "Last_Valid instead", N);
+                  when others =>
+                     null;
+               end case;
+            end;
+         end if;
+
          --  Emit an optional suggestion on how to remedy the error if the
          --  context warrants it.