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

  @return 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 |   @function nested() {
  |   ^^^^^^^^^^^^^^^^^^^
  '
  input.scss 2:3  root stylesheet