[Bug ada/106318] New: ICE when using 'Range in Ada22 Iterated Component Association

[cthowie at netzero dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106318

            Bug ID: 106318
           Summary: ICE when using 'Range in Ada22 Iterated Component
                    Association
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cthowie at netzero dot net
  Target Milestone: ---

PLATFORM: GCC 12.1.0 toolchain on Windows 10 Intel x64 using MSYS2 (Mingw64).

ISSUE: the use of 'Range sometimes causes an internal compiler error (ICE) when 
used in an Iterated Component Association per Ada 2022 syntax. Note that in the
example program below that illustrates the bug, I had to use a nested
subprogram, otherwise 'Range seemed to work OK in the Main subprogram itself:

In short, this syntax works:

   new Local_Array'(for I in Arr'First .. Arr'Last =>

but this syntax crashes GNAT:

   new Local_Array'(for I in Arr'Range =>

It seems a temporary workaround for the bug is to replace use of 'Range with
'First .. 'Last in cases where GNAT crashes ('Range isn't universally broken).


EXAMPLE PROGRAM DEMONSTRATING THE BUG
=====================================

--  COMPILE WITH: gnatmake main.adb -gnat2022
--  The code as it stands triggers an ICE as indicated in the comment below.
--  The culprit is the "for I in Arr'Range" being used in the Iterated 
--  Component Association syntax of Ada 2022.
--  If you comment out the line that "FAILS!", and uncomment the line that
"WORKS",
--  then you'll get stable code using Arr'First .. Arr'Last.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Unchecked_Deallocation;

procedure Main
is
   type Int_Array is array (Positive range <>) of Integer;
   type Int_Array_Acc is access Int_Array;
   procedure Free is new Ada.Unchecked_Deallocation (Int_Array, Int_Array_Acc);

   Foo : constant Int_Array := [1, 2, 3];

   procedure Nested                     --  replaces Arr with a similar one
      (Arr : in out Int_Array_Acc)
   is
      --  +===========================GNAT BUG ETECTED =============
      --  | 12.1.0 (x86_64-w64-mingw32) GCC error:
      --  | in gnat_to_gnu_entity, at ada/gcc-interface/decl.cc:472

      Replace : constant Int_Array_Acc :=
        --new Int_Array'(for I in Arr'First .. Arr'Last =>   --  THIS WORKS
        new Int_Array'(for I in Arr'Range =>                 --  THIS FAILS!
                       (if Arr (I) = 2
                        then 0
                        else Arr (I)));
   begin
      Free (Arr);
      Arr := Replace;
   end Nested;

   Goo : Int_Array_Acc := new Int_Array'(Foo);
begin
   Put_Line ("Goo =" & Goo.all'Image);  --  should print [ 1,  2,  3]
   Nested (Goo);
   Put_Line ("Goo =" & Goo.all'Image);  --  should print [ 1,  0,  3]
   Free (Goo);
end Main;