Index: sem_ch3.adb
===================================================================
--- sem_ch3.adb	(revision 160731)
+++ sem_ch3.adb	(working copy)
@@ -3750,10 +3750,10 @@
       if Present (Generic_Parent_Type (N))
         and then
           (Nkind
-             (Parent (Generic_Parent_Type (N))) /= N_Formal_Type_Declaration
+            (Parent (Generic_Parent_Type (N))) /= N_Formal_Type_Declaration
             or else Nkind
               (Formal_Type_Definition (Parent (Generic_Parent_Type (N))))
-                /=  N_Formal_Private_Type_Definition)
+                /= N_Formal_Private_Type_Definition)
       then
          if Is_Tagged_Type (Id) then
 
@@ -7356,6 +7356,27 @@
                   Exclude_Parents => True);
 
                Set_Interfaces (Derived_Type, Ifaces_List);
+
+               --  If the derived type is the anonymous type created for
+               --  a declaration whose parent has a constraint, propagate
+               --  the interface list to the source type. This must be done
+               --  prior to the completion of the analysis of the source type
+               --  because the components in the extension may contain current
+               --  instances whose legality depends on some ancestor.
+
+               if Is_Itype (Derived_Type) then
+                  declare
+                     Def : constant Node_Id :=
+                       Associated_Node_For_Itype (Derived_Type);
+                  begin
+                     if Present (Def)
+                       and then Nkind (Def) = N_Full_Type_Declaration
+                     then
+                        Set_Interfaces
+                          (Defining_Identifier (Def), Ifaces_List);
+                     end if;
+                  end;
+               end if;
             end;
          end if;
 
Index: exp_disp.adb
===================================================================
--- exp_disp.adb	(revision 160705)
+++ exp_disp.adb	(working copy)
@@ -1528,14 +1528,19 @@
       Formal        := First (Formals);
       while Present (Formal) loop
 
-         --  Handle concurrent types
+         --  Handle concurrent types.
 
          if Ekind (Target_Formal) = E_In_Parameter
            and then Ekind (Etype (Target_Formal)) = E_Anonymous_Access_Type
          then
             Ftyp := Directly_Designated_Type (Etype (Target_Formal));
          else
-            Ftyp := Etype (Target_Formal);
+
+            --  if the parent is a constrained discriminated type. the
+            --  primitive operation will have been defined on a first subtype.
+            --  for proper matching with controlling type, use base type.
+
+            Ftyp := Base_Type (Etype (Target_Formal));
          end if;
 
          if Is_Concurrent_Type (Ftyp) then