Proxy surprise

t-spec-S12-attributes-mutators.t

our $count = 0;

class MagicVal {
    has Int $.constant;
    has Int $.varies = 0;

    method varies is rw {
        $count++;
        return-rw Proxy.new(
            # note that FETCH and STORE cannot go through the accessors
            # of $.varies again, because that would lead to infinite
            # recursion. Use the actual attribute here instead
            FETCH => method ()     { $!varies  },
            STORE => method ($new) { $!varies = $new + 1 },
        );
    }
}

my $mv = MagicVal.new(:constant(6), :varies(6));
say $mv.varies.VAR.^name;   # Proxy
say $mv.varies.^name;       # Method