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[Ada] AI12-0352: Early derivation and equality of untagged types

Message ID 20201019095422.GA91209@adacore.com
State New
Headers show
Series [Ada] AI12-0352: Early derivation and equality of untagged types | expand

Commit Message

Pierre-Marie de Rodat Oct. 19, 2020, 9:54 a.m. UTC 
This AI clarifies that declaring a user-defined primitive equality
operation for a record type T is illegal if it occurs after a type has
been derived from T.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* sem_ch6.adb (Check_Untagged_Equality): Check for AI12-0352.
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Patch

diff --git a/gcc/ada/sem_ch6.adb b/gcc/ada/sem_ch6.adb
--- a/gcc/ada/sem_ch6.adb
+++ b/gcc/ada/sem_ch6.adb
@@ -9118,10 +9118,27 @@  package body Sem_Ch6 is
               ("equality operator appears too late (Ada 2012)?y?", Eq_Op);
          end if;
 
-      --  No error detected
+      --  Finally check for AI12-0352: declaration of a user-defined primitive
+      --  equality operation for a record type T is illegal if it occurs after
+      --  a type has been derived from T.
 
       else
-         return;
+         Obj_Decl := Next (Parent (Typ));
+
+         while Present (Obj_Decl) and then Obj_Decl /= Decl loop
+            if Nkind (Obj_Decl) = N_Full_Type_Declaration
+              and then Etype (Defining_Identifier (Obj_Decl)) = Typ
+            then
+               Error_Msg_N
+                 ("equality operator cannot appear after derivation", Eq_Op);
+               Error_Msg_NE
+                 ("an equality operator for& cannot be declared after "
+                  & "this point??",
+                  Obj_Decl, Typ);
+            end if;
+
+            Next (Obj_Decl);
+         end loop;
       end if;
    end Check_Untagged_Equality;