[gcc r13-7870] ada: Fix wrong result for membership test of null in null-excluding access type

[gcc r13-7870] ada: Fix wrong result for membership test of null in null-excluding access type

[Eric Botcazou]

https://gcc.gnu.org/g:34a2d742bfbec548058ed3a25d3e35ec180eb7c4

commit r13-7870-g34a2d742bfbec548058ed3a25d3e35ec180eb7c4
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Wed Apr 5 20:34:43 2023 +0200

    ada: Fix wrong result for membership test of null in null-excluding access type
    
    The result must be False as per the RM 4.5.2 (30.2/4) clause.
    
    gcc/ada/
    
            * exp_ch4.adb (Expand_N_In): Deal specifically with a null operand.

Diff:
---
 gcc/ada/exp_ch4.adb | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/exp_ch4.adb b/gcc/ada/exp_ch4.adb
index 0490a31a720..8442de6f90c 100644
--- a/gcc/ada/exp_ch4.adb
+++ b/gcc/ada/exp_ch4.adb
@@ -6964,11 +6964,13 @@ package body Exp_Ch4 is
 
                --  If the null exclusion checks are not compatible, need to
                --  perform further checks. In other words, we cannot have
-               --  Ltyp including null and Typ excluding null. All other cases
-               --  are OK.
+               --  Ltyp including null or Lop being null, and Typ excluding
+               --  null. All other cases are OK.
 
                Check_Null_Exclusion :=
-                 Can_Never_Be_Null (Typ) and then not Can_Never_Be_Null (Ltyp);
+                 Can_Never_Be_Null (Typ)
+                   and then (not Can_Never_Be_Null (Ltyp)
+                              or else Nkind (Lop) = N_Null);
                Typ := Designated_Type (Typ);
             end if;