[Ada] Do not overwrite limited view of result type

[Pierre-Marie de Rodat via Gcc-patches]

This removes obsolete code that overwrites a limited view present as the
result type of a function during the tentative analysis of prefixed
views for function calls involving tagged types. The original view is
necessary for the code generator to break the circularity present in
this setup.

The change also adds a couple of guards for the illegal case where the
limited view is the only view available when the function is invoked.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * aspects.adb (Find_Value_Of_Aspect): Add guard.
        * sem_ch4.adb (Complete_Object_Operation): Remove obsolete code.
        * sem_ch5.adb (Has_Sec_Stack_Default_Iterator): Add guard.
diff --git a/gcc/ada/aspects.adb b/gcc/ada/aspects.adb
--- a/gcc/ada/aspects.adb
+++ b/gcc/ada/aspects.adb
@@ -285,7 +285,9 @@ package body Aspects is
 
    begin
       if Present (Spec) then
-         if A = Aspect_Default_Iterator then
+         if A = Aspect_Default_Iterator
+           and then Present (Aspect_Rep_Item (Spec))
+         then
             return Expression (Aspect_Rep_Item (Spec));
          else
             return Expression (Spec);


diff --git a/gcc/ada/sem_ch4.adb b/gcc/ada/sem_ch4.adb
--- a/gcc/ada/sem_ch4.adb
+++ b/gcc/ada/sem_ch4.adb
@@ -9248,19 +9248,6 @@ package body Sem_Ch4 is
             Save_Interps (Subprog, Node_To_Replace);
 
          else
-            --  The type of the subprogram may be a limited view obtained
-            --  transitively from another unit. If full view is available,
-            --  use it to analyze call. If there is no nonlimited view, then
-            --  this is diagnosed when analyzing the rewritten call.
-
-            declare
-               T : constant Entity_Id := Etype (Subprog);
-            begin
-               if From_Limited_With (T) then
-                  Set_Etype (Entity (Subprog), Available_View (T));
-               end if;
-            end;
-
             Analyze (Node_To_Replace);
 
             --  If the operation has been rewritten into a call, which may get


diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb
--- a/gcc/ada/sem_ch5.adb
+++ b/gcc/ada/sem_ch5.adb
@@ -3675,6 +3675,7 @@ package body Sem_Ch5 is
          begin
             return
               Present (Def_Iter)
+                and then Present (Etype (Def_Iter))
                 and then Requires_Transient_Scope (Etype (Def_Iter));
          end Has_Sec_Stack_Default_Iterator;