[Ada] Wrong code on assignment of conditional expression to a mutable obkect

[Arnaud Charlet <charlet at adacore dot com>]

This patch fixes an error in an assignmen statement to an  entity of a mutable
type (variable or in-out parameter) when the righ-hand side of the assignment
is a conditioal expression, some of whose alternatives are aggregates. Prior
to this patch, not all components of the mutable object were properly
assigned the corresponding values of the aggregate.

Executing:

   gnatmake -q bug
   ./bug

must yield:

   local var  72
   local var  42
   in_out parameter  72
   in_out parameter  42

---

with Ada.Text_IO;

procedure Bug is

   type Yoyo (Exists : Boolean := False) is record
     case Exists is
       when False =>
         null;
       when True =>
         Value : Integer := 5;
     end case;
   end record;

   Var1 : Yoyo;
   Var2 : Yoyo;

   procedure Test (Condition : in Boolean;
                   Value     : in Integer;
                   Yo        : in out Yoyo) is
      Var3 : Yoyo;
   begin
     Yo := (if Condition then
              (Exists => True,
               Value  => Value)
            else
              (Exists => False));

     Var3 := (case condition is
               when True  => (Exists => True, Value => Value),
               when False => (Exists => False));

     if Condition and then
       Yo.Value /= Value then
       
       Ada.Text_IO.Put_Line ("Compiler bug exposed");
     end if;

     if Condition then
       Ada.Text_IO.Put_Line ("local var " & Integer'Image (Var3.Value));
     end if;

   end;

begin

   Test (True, 72, Var1);
   Test (True, 42, Var2);

   Ada.Text_IO.Put_Line ("in_out parameter " & Var1.Value'Img);
   Ada.Text_IO.Put_Line ("in_out parameter " & Var2.Value'Img);

   Test (False, 1000, Var1);

end Bug;

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

2017-09-06  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch5.adb (Analyze_Assigment): If the left-hand side is an
	entity of a mutable type and the right-hand side is a conditional
	expression, resolve the alternatives of the conditional using
	the base type of the target entity, because the alternatives
	may have distinct subtypes. This is particularly relevant if
	the alternatives are aggregates.

Attachment: difs
Description: Text document