ada: Analyze pre/post on access-to-subprogram without a wrapper

Aspects Pre/Post attached to an access-to-subprogram type were relocated
to a spec of a wrapper subprogram and analyzed there; the body of the
wrapper was only created with expansion enabled. However, there were
several problems with this approach.

When switch -gnat2022 was missing, we didn't relocate the Pre/Post
aspects to wrapper and complained that their placement is incorrect
(because we wrongly assumed that relocation is unconditional). Now we
gently inform, that these aspects are Ada 2022 features that require
-gnat20222 switch.

When switch -gnata was missing, we entirely bypassed analysis of the
Pre/Post aspects on access-to-subprogram. This was unlike for Pre/Post
aspects on subprograms, which are checked for legality regardless of the
-gnata switch.

Finally, in the GNATprove backend we were picking the Pre/Post contract
on an access-to-subprogram type from the wrapper, which was awkward as
otherwise we had to ignore the wrapper specs and special-case for their
missing bodies. In general, it is cleaner for GNATprove to extract the
aspect expressions from where they originally appear and not from
various expansion artifacts like access-to-subprogram wrappers (but the
same applies to predication functions, type invariant procedures and
default initialization procedures).

Now we analyze the Pre/Post aspects on the types where they are
originally attached, regardless of the -gnata switch. Once we adapt
GNATprove to pick the aspect expression from there, we will stop
creating the wrapper spec when expansion is disabled.

gcc/ada/

	* contracts.adb
	(Add_Pre_Post_Condition): Adapt to handle pre/post of an
	access-to-subprogram type.
	(Analyze_Type_Contract): Analyze pre/post of an
	access-to-subprogram.
	* contracts.ads
	(Analyze_Type_Contract): Adapt comment.
	* sem_ch3.adb
	(Build_Access_Subprogram_Wrapper): Copy pre/post aspects to
	wrapper spec and keep it on the type.
	* sem_prag.adb
	(Analyze_Pre_Post_Condition): Expect pre/post aspects on
	access-to-subprogram and complain if they appear without -gnat2022
	switch.
	(Analyze_Pre_Post_Condition_In_Decl_Part): Adapt to handle
	pre/post on an access-to-subprogram type entity.
	* sem_attr.adb (Analyze_Attribute_Old_Result): Likewise.
	(Result): Likewise.

1 files changed, 3 insertions, 12 deletions

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 634b1cb..f360be8 100644
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -6848,25 +6848,16 @@ package body Sem_Ch3 is
       declare
          Asp  : Node_Id;
          A_Id : Aspect_Id;
-         Cond : Node_Id;
-         Expr : Node_Id;
 
       begin
          Asp := First (Aspect_Specifications (Decl));
          while Present (Asp) loop
             A_Id := Get_Aspect_Id (Chars (Identifier (Asp)));
             if A_Id = Aspect_Pre or else A_Id = Aspect_Post then
-               Cond := Asp;
-               Expr := Expression (Cond);
-               Replace_Type_Name (Expr);
-               Next (Asp);
-
-               Remove (Cond);
-               Append (Cond, Contracts);
-
-            else
-               Next (Asp);
+               Append (New_Copy_Tree (Asp), Contracts);
+               Replace_Type_Name (Expression (Last (Contracts)));
             end if;
+            Next (Asp);
          end loop;
       end;