+ @if $prev-num == null or unit($num) == "%" or unit($prev-num) == "%" {
// Do nothing
} @else if not comparable($prev-num, $num) {
@warn "Potentially invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !";