Append function doesn't appear to append correctly inside loops

[cimmanon]

Tested against Sassmeister (running 3.3.2) and 3.3.1-52-gf89e

.parent {
    .brother, .sister, .cousin {
        color: green;
        sel: &;

        $new-sel: ();
        @each $s in & {
            $last: nth($s, -1);
            $new-sel: append($new-sel, $s #{'+'} $last, comma);
            x: $new-sel;
        }
        @at-root #{$new-sel} {
            debug: foo;
        }
    }
}

Ruby Sass Output:

.parent .brother, .parent .sister, .parent .cousin {
  color: green;
  x: .parent .brother + .brother;
  x: .parent .brother + .brother, .parent .sister + .sister;
  x: .parent .brother + .brother, .parent .sister + .sister, .parent .cousin + .cousin;
}
.parent .brother + .brother, .parent .sister + .sister, .parent .cousin + .cousin {
  debug: foo;
}

LibSass Output:

.parent .brother, .parent .sister, .parent .cousin {
  color: green;
  x: .parent .brother, .parent .sister, .parent .cousin + .parent .cousin;
}

.parent .brother, .parent .sister, .parent .cousin + .parent .cousin {
  debug: foo;
}

Note how LibSass doesn't show the intermediate values inside the loop (property x) and only the very last element in the list contains our adjacent sibling selector.

[xzyfer]

Thanks for the report @cimmanon. I can confirm this issue exists on master.

We're in need of a more specific test case.

[mgreter]

Fixed with #1757