<===> input.scss
$map: (
  foo: fump,
  bar: bump,
);

@mixin vararg-test($foo, $bar) {
  foo: $foo;
  bar: $bar;
}

.test {
  @include vararg-test($map...);
}

<===> output.css
.test {
  foo: fump;
  bar: bump;
}