[Ada] Fix explicit raise on subtype of lock-free protected type

[Eric Botcazou]

The problem is that the Uses_Lock_Free flag is not propagated to the subtype.

Tested on x86-64/Linux, applied on the mainline.


2025-11-04  Eric Botcazou  <ebotca...@adacore.com>

        PR ada/84320
        * sem_ch3.adb (Analyze_Subtype_Declaration) <Concurrent_Kind>:
        Propagate the Uses_Lock_Free flag for protected types.


2025-11-04  Eric Botcazou  <ebotca...@adacore.com>

        * gnat.dg/protected_subtype1.adb: New test.

-- 
Eric Botcazou
-- { dg-do compile }

procedure Protected_Subtype1 is

   protected type Object with Lock_Free => True is
   end Object;

   protected body Object is
   end Object;

   A : Object;

   subtype Object_Subtype is Object;

   B : Object_Subtype;

   type Rec is record
      A : Object;         
      B : Object_Subtype;
   end record;

   C : Rec;

begin
  null;
end;

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 233f8237aa5..ba0af27471d 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -6145,6 +6145,10 @@ package body Sem_Ch3 is
                Set_Is_Tagged_Type       (Id, Is_Tagged_Type        (T));
                Set_Last_Entity          (Id, Last_Entity           (T));
 
+               if Is_Protected_Type (T) then
+                  Set_Uses_Lock_Free (Id, Uses_Lock_Free (T));
+               end if;
+
                if Is_Tagged_Type (T) then
                   Set_No_Tagged_Streams_Pragma
                     (Id, No_Tagged_Streams_Pragma (T));