[gcc r13-7840] ada: Fix deferred constant wrongly rejected

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:35787c3093fa611ba46008e94f329000d6042be4

commit r13-7840-g35787c3093fa611ba46008e94f329000d6042be4
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Sat Sep 16 20:29:20 2023 +0200

    ada: Fix deferred constant wrongly rejected
    
    This recent regression occurs when the nominal subtype of the constant is a
    discriminated record type with default discriminants.
    
    gcc/ada/
            PR ada/110488
            * sem_ch3.adb (Analyze_Object_Declaration): Do not build a default
            subtype for a deferred constant in the definite case too.

Diff:
---
 gcc/ada/sem_ch3.adb | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 299ea6e989f..7aa13b86607 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -4956,9 +4956,11 @@ package body Sem_Ch3 is
             Apply_Length_Check (E, T);
          end if;
 
-      --  When possible, build the default subtype
+      --  When possible, and not a deferred constant, build the default subtype
 
-      elsif Build_Default_Subtype_OK (T) then
+      elsif Build_Default_Subtype_OK (T)
+        and then (not Constant_Present (N) or else Present (E))
+      then
          if No (E) then
             Act_T := Build_Default_Subtype (T, N);
          else