<===> input.scss
.foo {
    content: call('unquote', 'foo', ()...);
}

<===> output.css
.foo {
  content: foo;
}

<===> warning
DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Sass 4.0. Use call(function-reference(unquote)) instead.

<===> warning-dart-sass
DEPRECATION WARNING: Passing a string to call() is deprecated and will be illegal
in Dart Sass 2.0.0. Use call(get-function("unquote")) instead.

  ,
2 |     content: call('unquote', 'foo', ()...);
  |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  '
    input.scss 2:14  root stylesheet