[Ada] Improve unnesting for discriminants of record subtypes

2018-05-28  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_unst.adb (Check_Static_Type): For a record subtype, check
	discriminant constraints as well.
	(Visit_Node): For a selected component, check type of prefix, as is
	done for indexed components and slices.

From-SVN: r260838

gcc/ada/ChangeLog

+2018-05-28  Ed Schonberg  <schonberg@adacore.com>
+
+	* exp_unst.adb (Check_Static_Type): For a record subtype, check
+	discriminant constraints as well.
+	(Visit_Node): For a selected component, check type of prefix, as is
+	done for indexed components and slices.
+
 2018-05-28  Javier Miranda  <miranda@adacore.com>
 
 	* exp_ch4.adb (Real_Range_Check): Add a temporary to store the integer

gcc/ada/exp_unst.adb

@@ -481,17 +481,34 @@ package body Exp_Unst is
                      end if;
                   end;
 
-               --  For record type, check all components
+               --  For record type, check all components and discriminant
+               --  constraints if present.
 
                elsif Is_Record_Type (T) then
                   declare
                      C : Entity_Id;
+                     D : Elmt_Id;
+
                   begin
                      C := First_Component_Or_Discriminant (T);
                      while Present (C) loop
                         Check_Static_Type (Etype (C), N, DT);
                         Next_Component_Or_Discriminant (C);
                      end loop;
+
+                     if Has_Discriminants (T)
+                       and then Present (Discriminant_Constraint (T))
+                     then
+                        D := First_Elmt (Discriminant_Constraint (T));
+                        while Present (D) loop
+                           if not Is_Static_Expression (Node (D)) then
+                              Note_Uplevel_Bound (Node (D), N);
+                              DT := True;
+                           end if;
+
+                           Next_Elmt (D);
+                        end loop;
+                     end if;
                   end;
 
                --  For array type, check index types and component type
@@ -685,6 +702,18 @@ package body Exp_Unst is
                   Check_Static_Type (Etype (Prefix (N)), Empty, DT);
                end;
 
+            --  A selected component can have an implicit up-level reference
+            --  due to the bounds of previous fields in the record. We
+            --  simplify the processing here by examining all components
+            --  of the record.
+
+            elsif Nkind (N) = N_Selected_Component then
+               declare
+                  DT : Boolean := False;
+               begin
+                  Check_Static_Type (Etype (Prefix (N)), Empty, DT);
+               end;
+
             --  Record a subprogram. We record a subprogram body that acts as
             --  a spec. Otherwise we record a subprogram declaration, providing
             --  that it has a corresponding body we can get hold of. The case