<===> input.scss
@function foo () {
  @mixin bar() {}
}
<===> error
Error: Functions can only contain variable declarations and control directives.
        on line 2 of input.scss
  Use --trace for backtrace.

<===> error-dart-sass
Error: This at-rule is not allowed here.
  ,
2 |   @mixin bar() {}
  |   ^^^^^^^^^^^^^
  '
  input.scss 2:3  root stylesheet