<===> input.scss
@mixin c() {
  @error test;
  c: d;
}

a {
  b: {
    @include c();
  }
}

<===> error
Error: test
        on line 2 of input.scss, in `c'
        from line 8 of input.scss
  Use --trace for backtrace.

<===> error-dart-sass
Error: test
  ,
8 |     @include c();
  |     ^^^^^^^^^^^^
  '
  input.scss 8:5  root stylesheet