with-attributes.pl

use v6;

sub with-attributes ($obj, *&callback) {
    my %slot-values;
    for &callback.signature.params -> $param {
        my $slot = $param.name.substr(1);
        %slot-values{$slot} = $obj."$slot"();
    }
    callback |%slot-values;
}

use Test;

class Thing {
    has $.x is rw;
    has $.y is rw;
}

my Thing $thing .= new(x => 0, y => 1);

is $thing.x, 0, 'Correct initial $thing.x.';
is $thing.y, 1, 'Correct initial $thing.y.';

with-attributes $thing, -> $x, $y {
    is $x, 0, 'with-attributes works for reading $thing.x.';
    is $y, 1, 'with-attributes works for reading $thing.y.';
}

with-attributes $thing, -> $x is rw, $y is rw {
    $x++;
    $y++;
    is $x, 1, 'with-attributes allows modifying local $x value with is rw.';
    is $y, 2, 'with-attributes allows modifying local $y value with is rw.';
}

is $thing.x, 1, 'Changes to $thing.x in with-attributes persist outside of the block.';
is $thing.y, 2, 'Changes to $thing.y in with-attributes persist outside of the block.';

done_testing;

Current output is:

ok 1 - Correct initial $thing.x.
ok 2 - Correct initial $thing.y.
ok 3 - with-attributes works for reading $thing.x.
ok 4 - with-attributes works for reading $thing.y.
ok 5 - with-attributes allows modifying local $x value with is rw.
ok 6 - with-attributes allows modifying local $y value with is rw.
not ok 7 - Changes to $thing.x in with-attributes persist outside of the block.

got: '0'

expected: '1'

not ok 8 - Changes to $thing.y in with-attributes persist outside of the block.

got: '1'

expected: '2'

1..8

Looks like you failed 2 tests of 8