[COMMITTED] ada: Make Apply_Discriminant_Check.Denotes_Explicit_Dereference more robust

[COMMITTED] ada: Make Apply_Discriminant_Check.Denotes_Explicit_Dereference more robust

[Marc Poulhiès]

From: Eric Botcazou <ebotcazou@adacore.com>

The predicate implements the rules of the language so it needs to cope with
constructs rewritten by the expander, in particular explicit dereferences
that the expander uses liberally for various purposes.

This change makes the detection of rewritten calls more robust and adds the
detection of rewritten return objects.

gcc/ada/

	* checks.adb (Apply_Discriminant_Check.Denotes_Explicit_Dereference):
	Return false for artificial dereferences generated by the expander.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/checks.adb | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
index 5833be3a5de..d518e6720a2 100644
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -1388,13 +1388,23 @@ package body Checks is
 
       function Denotes_Explicit_Dereference (Obj : Node_Id) return Boolean is
       begin
-         return
-           Nkind (Obj) = N_Explicit_Dereference
-             or else
-               (Is_Entity_Name (Obj)
-                 and then Present (Renamed_Object (Entity (Obj)))
-                 and then Nkind (Renamed_Object (Entity (Obj))) =
-                                              N_Explicit_Dereference);
+         if Is_Entity_Name (Obj) then
+            return Present (Renamed_Object (Entity (Obj)))
+              and then
+                Denotes_Explicit_Dereference (Renamed_Object (Entity (Obj)));
+
+         --  This routine uses the rules of the language so we need to exclude
+         --  rewritten constructs that introduce artificial dereferences.
+
+         elsif Nkind (Obj) = N_Explicit_Dereference then
+            return not Is_Captured_Function_Call (Obj)
+              and then not
+                (Nkind (Parent (Obj)) = N_Object_Renaming_Declaration
+                  and then Is_Return_Object (Defining_Entity (Parent (Obj))));
+
+         else
+            return False;
+         end if;
       end Denotes_Explicit_Dereference;
 
       ----------------------------------------
@@ -1497,9 +1507,7 @@ package body Checks is
                              and then not Is_Aliased_Unconstrained_Component)
                    or else (Ada_Version >= Ada_2005
                              and then not Is_Constrained (T_Typ)
-                             and then Denotes_Explicit_Dereference (Lhs)
-                             and then Nkind (Original_Node (Lhs)) /=
-                                        N_Function_Call))
+                             and then Denotes_Explicit_Dereference (Lhs)))
       then
          T_Typ := Get_Actual_Subtype (Lhs);
       end if;
-- 
2.34.1