Why can I not migrate a supply in a whenever block of a unix socket?

Question

server

#!/usr/bin/env raku

unlink "/run/user/1000/sock";
my $socket = IO::Socket::Async.listen-path("/run/user/1000/sock");

react {
  my $timerSupplier = Supplier.new;

  whenever $timerSupplier.Supply.migrate {
    say "3 second interval: ", $_;
  }
  $timerSupplier.emit(Supply.interval(3));

  whenever $socket -> $conn {
    $timerSupplier.emit(Supply.interval(3));
    say "\"", $_.Supply.lines.Channel.receive, "\"";
    $conn.close;
  }
}

client

#!/usr/bin/env raku

my $sock = IO::Socket::Async.connect-path("/run/user/1000/sock").result;
await $sock.print("ok\n");

If I execute server and then client, I get the following exception.

Unhandled exception in code scheduled on thread 8
Can only cancel an AsyncTask handle
  in block  at ./server line 16

Can anyone tell me what is the problem?

Answer 1

Replacing

  whenever $socket -> $conn {
    $timerSupplier.emit(Supply.interval(3));
    say "\"", $_.Supply.lines.Channel.receive, "\"";
    $conn.close;
  }

with

  whenever $socket -> $conn {
    $timerSupplier.emit(Supply.interval(3));
    say "\"", $conn.Supply.lines.Channel.receive, "\"";
    $conn.close;
  }

fixed the error. It seems if a block has a named parameter, the topic variable stops working.