<===> input.scss
@function parent() {
  @mixin nested {
    foo: bar;
  }

  @include nested;
}


test {
  foo: parent();
}

<===> 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 nested {
  |   ^^^^^^^^^^^^^^
  '
  input.scss 2:3  root stylesheet