locked-by raku trait

README.md

see also https://gitlab.com/-/snippets/2558851

l.raku

use v6.d;
use lib '.';
use LockedBy;

class Counter {
    has Lock $.one = Lock.new;
    has Int $counter = 0;

    # access the lock as private attribute
    method increment() is locked-by<$!one> { ++$!counter }
    # access the lock as public method
    method get() is locked-by<one> { $!counter }
}

my $c = Counter.new;
$c.increment();
say $c.get;

LockedBy.rakumod

use v6.d;

multi sub trait_mod:<is>(Method $r, Str:D :$locked-by!) is export {
    $r.wrap(method (|capture) {
                   my $lock := ($locked-by ~~ /^ '$!' /)
                   ?? self.^attribute_table(){$locked-by}.get_value(self)
                   !! self."$locked-by"();

                   my &next := nextcallee;
                   my $result;

                   $lock.protect(
                       -> { $result := next(self, |capture) }
                   );
                   return $result;
               });
}