[gcc r16-1338] ada: Clarify code in Process_Subtype

[Marc Poulhies]

https://gcc.gnu.org/g:3280bce431be5afb260fe59d01ef1deee38704e8

commit r16-1338-g3280bce431be5afb260fe59d01ef1deee38704e8
Author: Ronan Desplanques <desplanques@adacore.com>
Date:   Fri Mar 14 14:41:56 2025 +0100

    ada: Clarify code in Process_Subtype
    
    This patch factorizes two if statements together in the body of
    Process_Subtype, to improve readability.
    
    gcc/ada/ChangeLog:
    
            * sem_ch3.adb (Process_Subtype): Clarify code.

Diff:
---
 gcc/ada/sem_ch3.adb | 90 +++++++++++++++++++++++++----------------------------
 1 file changed, 43 insertions(+), 47 deletions(-)

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 6c2d0326c3f9..9d93bf79c0ce 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -22579,63 +22579,59 @@ package body Sem_Ch3 is
          Check_Incomplete (S);
          P := Parent (S);
 
-         --  Ada 2005 (AI-231): Static check
+         if Excludes_Null then
+            --  Create an Itype that is a duplicate of Entity (S) but with the
+            --  null-exclusion attribute.
+            if Is_Access_Type (Entity (S)) then
+               if Can_Never_Be_Null (Entity (S)) then
+                  case Nkind (Related_Nod) is
+                     when N_Full_Type_Declaration =>
+                        if Nkind (Type_Definition (Related_Nod))
+                           in N_Array_Type_Definition
+                        then
+                           Error_Node :=
+                             Subtype_Indication
+                               (Component_Definition
+                                  (Type_Definition (Related_Nod)));
+                        else
+                           Error_Node :=
+                             Subtype_Indication
+                               (Type_Definition (Related_Nod));
+                        end if;
 
-         if Ada_Version >= Ada_2005
-           and then Excludes_Null
-           and then not Is_Access_Type (Entity (S))
-         then
-            Error_Msg_N ("`NOT NULL` only allowed for an access type", S);
-         end if;
+                     when N_Subtype_Declaration =>
+                        Error_Node := Subtype_Indication (Related_Nod);
 
-         --  Create an Itype that is a duplicate of Entity (S) but with the
-         --  null-exclusion attribute.
+                     when N_Object_Declaration =>
+                        Error_Node := Object_Definition (Related_Nod);
 
-         if Is_Access_Type (Entity (S)) and then Excludes_Null then
-            if Can_Never_Be_Null (Entity (S)) then
-               case Nkind (Related_Nod) is
-                  when N_Full_Type_Declaration =>
-                     if Nkind (Type_Definition (Related_Nod))
-                       in N_Array_Type_Definition
-                     then
+                     when N_Component_Declaration =>
                         Error_Node :=
                           Subtype_Indication
-                            (Component_Definition
-                             (Type_Definition (Related_Nod)));
-                     else
-                        Error_Node :=
-                          Subtype_Indication (Type_Definition (Related_Nod));
-                     end if;
+                            (Component_Definition (Related_Nod));
 
-                  when N_Subtype_Declaration =>
-                     Error_Node := Subtype_Indication (Related_Nod);
+                     when N_Allocator =>
+                        Error_Node := Expression (Related_Nod);
 
-                  when N_Object_Declaration =>
-                     Error_Node := Object_Definition (Related_Nod);
+                     when others =>
+                        pragma Assert (False);
+                        Error_Node := Related_Nod;
+                  end case;
 
-                  when N_Component_Declaration =>
-                     Error_Node :=
-                       Subtype_Indication (Component_Definition (Related_Nod));
-
-                  when N_Allocator =>
-                     Error_Node := Expression (Related_Nod);
-
-                  when others =>
-                     pragma Assert (False);
-                     Error_Node := Related_Nod;
-               end case;
+                  Error_Msg_NE
+                    ("`NOT NULL` not allowed (& already excludes null)",
+                     Error_Node,
+                     Entity (S));
+               end if;
 
-               Error_Msg_NE
-                 ("`NOT NULL` not allowed (& already excludes null)",
-                  Error_Node,
-                  Entity (S));
+               Set_Etype
+                 (S,
+                  Create_Null_Excluding_Itype
+                    (T => Entity (S), Related_Nod => P));
+               Set_Entity (S, Etype (S));
+            elsif Ada_Version >= Ada_2005 then
+               Error_Msg_N ("`NOT NULL` only allowed for an access type", S);
             end if;
-
-            Set_Etype  (S,
-              Create_Null_Excluding_Itype
-                (T           => Entity (S),
-                 Related_Nod => P));
-            Set_Entity (S, Etype (S));
          end if;
 
          return Entity (S);