infinite supply {} + react {} = hang

supply-test.p6

# Use most advanced version of await/react/etc.
use v6.d.PREVIEW;

# Externally stoppable infinite supply
sub make-supply() {
    my $done = False;
    supply {
        until $done {
            say "Emitting ...";
            emit(++$);
        }
    } does role { method done { $done = True } }
}

# This works as expected, emit and receive paired, and ends after 5
say "USING .act";
my $s1 = make-supply;
$s1.act: -> $n {
    say "Received $n";
    $s1.done if $n >= 5;
}

# This appears to try to exhaust the supply *before* receiving anything
say "\nUSING react";
my $s2 = make-supply;
react {
    whenever $s2 -> $n {
        say "Received $n";
        $s1.done if $n >= 5;
    }
}