exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Bugfix in renaming of…

exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Bugfix in renaming of discriminant for mutable record type.

	* exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Bugfix in
	renaming of discriminant for mutable record type.

From-SVN: r46222

gcc/ada/ChangeLog

+2001-10-11  Ed Schonberg  <schonber@gnat.com>
+
+	* exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Bugfix in 
+	renaming of discriminant for mutable record type.
+
 2001-10-11  Robert Dewar  <dewar@gnat.com>
 
 	* validsw.adb: Properly save -gnatVn status.

gcc/ada/exp_ch8.adb

@@ -6,7 +6,7 @@
 --                                                                          --
 --                                 B o d y                                  --
 --                                                                          --
---                            $Revision: 1.27 $
+--                            $Revision$
 --                                                                          --
 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
 --                                                                          --
@@ -67,6 +67,16 @@ package body Exp_Ch8 is
    --  to the object will be handled by macro substitution in the front
    --  end, and the back end will know to ignore the renaming declaration.
 
+   --  An additional odd case that requires processing by expansion is
+   --  the renaming of a discriminant of a mutable record type. The object
+   --  is a constant because it renames something that cannot be assigned to,
+   --  but in fact the underlying value can change and must be reevaluated
+   --  at each reference. Gigi does have a notion of a "constant view" of
+   --  an object, and therefore the front-end must perform the expansion.
+   --  For simplicity, and to bypass some obscure code-generation problem,
+   --  we use macro substitution for all renamed discriminants, whether the
+   --  enclosing type is constrained or not.
+
    --  The other special processing required is for the case of renaming
    --  of an object of a class wide type, where it is necessary to build
    --  the appropriate subtype for the renamed object.
@@ -203,6 +213,13 @@ package body Exp_Ch8 is
          elsif Nkind (Nam) = N_Selected_Component then
             if Present (Component_Clause (Entity (Selector_Name (Nam)))) then
                return True;
+
+            elsif Ekind (Entity (Selector_Name (Nam))) = E_Discriminant
+              and then Is_Record_Type (Etype (Prefix (Nam)))
+              and then not Is_Concurrent_Record_Type (Etype (Prefix (Nam)))
+            then
+               return True;
+
             else
                return Evaluation_Required (Prefix (Nam));
             end if;