<===> input.scss
@mixin a {
  b: c;
}

@include a();
<===> error
Error: Properties are only allowed within rules, directives, mixin includes, or other properties.
        on line 2 of input.scss
  Use --trace for backtrace.

<===> error-dart-sass
Error: Declarations may only be used within style rules.
  ,
2 |   b: c;
  |   ^^^^
  '
  input.scss 2:3  a()
  input.scss 5:1  root stylesheet