[perl #127238] Undefined loop variable inside sub [BUG]

[via RT]

# New Ticket Created by  Iskander Sharipov 
# Please include the string:  [perl #127238]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127238 >


VERSION:
$ perl6 --version
This is Rakudo version 2015.12-44-g477830a built on MoarVM version 2015.12
implementing Perl 6.c.

CODE:
use v6;
sub bug {
    loop (my $i = 0; $i < 5; ++$i) { say $i; }
}
bug;

ERROR:
Cannot call infix:«<»(Any, Int); none of these signatures match:
    ($?)
    (\a, \b)
    (Real \a, Real \b)
    (Int:D \a, Int:D \b)
    (int $a, int $b)
    (Num:D \a, Num:D \b --> Bool)
    (num $a, num $b --> Bool)
    (Rational:D \a, Rational:D \b)
    (Rational:D \a, Int:D \b)
    (Int:D \a, Rational:D \b)
    (Instant:D $a, Instant:D $b)
    (DateTime:D \a, DateTime:D \b)
    (Date:D $a, Date:D $b)
  in block <unit> at loop.pl6 line 4

CAUSE:
Loop initialization of $i is not working in this case.
If we put loop out of the sub routine - everything is fine.

ENV:
$ uname -a
3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt17-1 (2015-09-26) x86_64 GNU/Linux

Iskander Sharipov - Quasilyte