[perl #130920] Tap's closing callback doesn't call back

[brian d foy]

# New Ticket Created by  "brian d foy" 
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This is the example from the Tap docs. I expect the output to be
"Tap closed", but I get no output using 2017.01:

    my $s = Supplier.new;
    my $tap = $s.Supply.tap(
        -> $v { say "the value is $v" },
        done    => { say "Supply is done" },
        closing => { say "Tap closed" },
        quit    => -> $ex { say "Supply finished with error $ex" },
    );

    # later
    $tap.close;