Spot the bug in the Sass entry

Dart Sass 1.104.0 intermediate 4 min 1 issue to find

Why does this entry fail before it emits CSS?

scss

.card {
  color: #1f2937;
}

@use "sass:color";

.card--muted {
  color: color.adjust(#1f2937, $lightness: 20%);
}