input.scss

This is a hacky syntax that css-modules uses to define dependecies across files, in general we'd want sass to ignore it, which is what the other sasses do.

:import("./foo") {
  color: red;
}

Actual results

libsass 3.5.4

Invalid CSS after ":import(": expected selector, was '"./foo") {' on line 1 at column 1

Expected result

This is what dart and ruby sass compile to

:import("./foo") {
  color: red;
}