[Ada] Expansion of Ada2012 predicate checks for type conversions

[Arnaud Charlet]

This patch fixes an infinite recursion in the application of predicate checks
to type conversions.

The following must compile quietly:

    gcc -c -gnat12 ./why-conversions.ads

---
with Why.Ids; use Why.Ids;
package Why.Conversions is

   function "+"
     (Id : W_Unused_At_Start_OId)
     return W_Unused_At_Start_Valid_OId;
private

   function "+"
     (Id : W_Unused_At_Start_OId)
     return W_Unused_At_Start_Valid_OId is
     (W_Unused_At_Start_Valid_OId (Id));
end Why.Conversions;
---
package Why is
   pragma Pure;
end Why;
---
with Why.Unchecked_Ids; use Why.Unchecked_Ids;
package Why.Ids is

   subtype W_Unused_At_Start_Valid_OId is
     W_Unused_At_Start_Unchecked_OId;

   type W_Unused_At_Start_OId is new
     W_Unused_At_Start_Valid_OId;
end Why.Ids;
---
with Why.Opaque_Ids;   use Why.Opaque_Ids;
package Why.Kind_Validity is
   --  Kind-validity checks

   function Unused_At_Start_OId_Kind_Valid
     (Id : W_Unused_At_Start_Opaque_OId)
     return Boolean;

private

   function Unused_At_Start_OId_Kind_Valid
     (Id : W_Unused_At_Start_Opaque_OId)
     return Boolean is
     (Id /= 0);
end Why.Kind_Validity;
---
package Why.Opaque_Ids is
   subtype W_Unused_At_Start_Opaque_OId is Integer;
end Why.Opaque_Ids;
---
with Why.Opaque_Ids;    use Why.Opaque_Ids;
with Why.Kind_Validity; use Why.Kind_Validity;
package Why.Unchecked_Ids is
   subtype W_Unused_At_Start_Unchecked_OId is
     W_Unused_At_Start_Opaque_OId  with
    Predicate =>
      (Unused_At_Start_OId_Kind_Valid
       (W_Unused_At_Start_Unchecked_OId));
end Why.Unchecked_Ids;

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

2011-08-05  Ed Schonberg  <schonb...@adacore.com>

        * exp_ch4.adb (Expand_N_Type_Conversion): When expanding a predicate
        check, indicate that the copy of the original node does not come from
        source, to prevent an infinite recursion of the expansion.


Index: exp_ch4.adb
===================================================================
--- exp_ch4.adb (revision 177431)
+++ exp_ch4.adb (working copy)
@@ -9154,8 +9154,16 @@
         and then Target_Type /= Operand_Type
         and then Comes_From_Source (N)
       then
-         Insert_Action (N,
-           Make_Predicate_Check (Target_Type, Duplicate_Subexpr (N)));
+         declare
+            New_Expr : constant Node_Id := Duplicate_Subexpr (N);
+
+         begin
+            --  Avoid infinite recursion on the subsequent expansion of
+            --  of the copy of the original type conversion.
+
+            Set_Comes_From_Source (New_Expr, False);
+            Insert_Action (N, Make_Predicate_Check (Target_Type, New_Expr));
+         end;
       end if;
    end Expand_N_Type_Conversion;