<===> input.scss
@function foo($a, $b: null, $c: false) {
  @return $c;
}

@function bar($args...) {
  @return call(foo, $args...);
}

test {
  test: bar(3, $c: true);
}

<===> output.css
test {
  test: true;
}

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

  ,
6 |   @return call(foo, $args...);
  |           ^^^^^^^^^^^^^^^^^^^
  '
    input.scss 6:11  bar()
    input.scss 10:9  root stylesheet