[Ada] Fix assertion failure on derived private protected type

This fixes an assertion failure on the instantiation of a generic
package on a type derived from the private view of a protected type,
ultimately caused by Finalize_Address returning Empty for the subtype
built for the generic actual type of the instantiation.

Finalize_Address has a special processing for untagged derivations of
private views, but it would no longer trigger for the subtype because
this subtype is now represented as a subtype of an implicit derived base
type instead of as the derived type of an implicit subtype previously.

2019-08-21  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_util.adb (Finalize_Address): Deal consistently with
	subtypes of private protected types.

gcc/testsuite/

	* gnat.dg/prot9.adb, gnat.dg/prot9_gen.ads,
	gnat.dg/prot9_pkg1.ads, gnat.dg/prot9_pkg2.ads: New testcase.

From-SVN: r274778

gcc/ada/ChangeLog

+2019-08-21  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* exp_util.adb (Finalize_Address): Deal consistently with
+	subtypes of private protected types.
+
 2019-08-21  Piotr Trojanek  <trojanek@adacore.com>
 
 	* exp_util.adb (Corresponding_Runtime_Package): Use high-level

gcc/ada/exp_util.adb

@@ -5347,6 +5347,7 @@ package body Exp_Util is
    ----------------------
 
    function Finalize_Address (Typ : Entity_Id) return Entity_Id is
+      Btyp : constant Entity_Id := Base_Type (Typ);
       Utyp : Entity_Id := Typ;
 
    begin
@@ -5386,12 +5387,12 @@ package body Exp_Util is
       --  records do not automatically inherit operations, but maybe they
       --  should???)
 
-      if Is_Untagged_Derivation (Typ) then
-         if Is_Protected_Type (Typ) then
-            Utyp := Corresponding_Record_Type (Root_Type (Base_Type (Typ)));
+      if Is_Untagged_Derivation (Btyp) then
+         if Is_Protected_Type (Btyp) then
+            Utyp := Corresponding_Record_Type (Root_Type (Btyp));
 
          else
-            Utyp := Underlying_Type (Root_Type (Base_Type (Typ)));
+            Utyp := Underlying_Type (Root_Type (Btyp));
 
             if Is_Protected_Type (Utyp) then
                Utyp := Corresponding_Record_Type (Utyp);

gcc/testsuite/ChangeLog

+2019-08-21  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/prot9.adb, gnat.dg/prot9_gen.ads,
+	gnat.dg/prot9_pkg1.ads, gnat.dg/prot9_pkg2.ads: New testcase.
+
 2019-08-21  Javier Miranda  <miranda@adacore.com>
 
 	* gnat.dg/implicit_param.adb, gnat.dg/implicit_param_pkg.ads:

gcc/testsuite/gnat.dg/prot9.adb

+--  { dg-do compile }
+
+with Prot9_Gen;
+with Prot9_Pkg1;
+
+procedure Prot9 is
+   package Dummy is new Prot9_Gen (Prot9_Pkg1.Prot_Type);
+begin
+   null;
+end Prot9;

gcc/testsuite/gnat.dg/prot9_gen.ads

+generic
+  type Field_Type is limited private;
+package Prot9_Gen is
+
+  type Field_Pointer is access all Field_Type;
+
+  Pointer : Field_Pointer := new Field_Type;
+
+end Prot9_Gen;

gcc/testsuite/gnat.dg/prot9_pkg1.ads

+with Prot9_Pkg2;
+
+package Prot9_Pkg1 is
+
+   type Prot_Type is limited private;
+
+private
+
+   type Prot_Type is new Prot9_Pkg2.Prot_Type;
+
+end Prot9_Pkg1;

gcc/testsuite/gnat.dg/prot9_pkg2.ads

+with Ada.Containers.Doubly_Linked_Lists;
+
+package Prot9_Pkg2 is
+
+   type Prot_type is limited private;
+
+private
+
+   package My_Lists is new Ada.Containers.Doubly_Linked_Lists (Integer);
+
+   protected type Prot_type is
+   private
+     L : My_Lists.List;
+   end Prot_type;
+
+end Prot9_Pkg2;