[Ada] Missing validity check on record type component

[Pierre-Marie de Rodat]

The compiler may silently skip generating a validity check on a
type conversion of a component of a record type. After this patch
the error is reported on the following sources.

pragma Initialize_Scalars;
package Pkg is
   type T is record
      Major : Natural;
      Minor : Natural;
   end record;

   procedure Do_Test (Value : in out T);
end;

pragma Initialize_Scalars;
package body Pkg is
   type    Integer_T is range -2 ** 31 .. 2 ** 31 - 1;
   subtype Natural_T is Integer_T range 0 .. Integer_T'Last;
   Next_Val : Integer_T := 0;

   procedure Do_Update (Int : in out Integer_T) is
   begin
      Next_Val := Next_Val + 1;
      if Next_Val > 1000 then
         Next_Val := Int;
      else
         Int := Next_Val;
      end if;
   end;

   procedure Do_Test (Value : in out T) is
   begin
      Do_Update (Natural_T (Value.Minor));   -- Run-time error
   end;

end;

with Pkg; use Pkg;
procedure Main is
   Obj : T;
begin
   Do_Test (Obj);
end Main;

Command: gnatmake -q -gnatVaM main.adb; ./main
Output:
  raised CONSTRAINT_ERROR : pkg.adb:20 invalid data

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

2017-10-14  Javier Miranda  <mira...@adacore.com>

        * checks.adb (Ensure_Valid): Do not skip adding the validity check on
        renamings of objects that come from the sources.


Index: checks.adb
===================================================================
--- checks.adb  (revision 253753)
+++ checks.adb  (working copy)
@@ -5940,6 +5940,10 @@
       --  In addition, we force a check if Force_Validity_Checks is set
 
       elsif not Comes_From_Source (Expr)
+        and then not
+          (Nkind (Expr) = N_Identifier
+            and then Present (Renamed_Object (Entity (Expr)))
+            and then Comes_From_Source (Renamed_Object (Entity (Expr))))
         and then not Force_Validity_Checks
         and then (Nkind (Expr) /= N_Unchecked_Type_Conversion
                     or else Kill_Range_Check (Expr))