Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.1.0)
// ----

@import 'susy';

$susy: (columns: 4);
$map: (columns: 4);

// doesn't work
@mixin inherit-layout($layout: 4) {
  columns: $layout;
}

// works
@mixin inherit-susy-map($layout: map-get($susy, 'columns')) {
  columns: $layout;
}

// doesn't work
@mixin inherit-my-map($layout: map-get($map, 'columns')) {
  columns: $layout;
}

// No map specified
@include susy-breakpoint(30em) {
  .global-cols {
    @include inherit-layout();
    @include inherit-susy-map();
    @include inherit-my-map();
  }
}

// Map specified
@include susy-breakpoint(48em, $layout: 8) {
  .inherited-cols {
    @include inherit-layout();
     /* OMGWTFBBQ it inherited context, BUT WHY!? */
    @include inherit-susy-map();
    @include inherit-my-map();
  }
}

SassMeister-output.css

@media (min-width: 30em) {
  .global-cols {
    columns: 4;
    columns: 4;
    columns: 4; } }

@media (min-width: 48em) {
  .inherited-cols {
    columns: 4;
    /* OMGWTFBBQ it inherited context, BUT WHY!? */
    columns: 8;
    columns: 4; } }