problem with sass media queries + variables

Gemfile

source :rubygems

gem 'fssm'
gem 'sass', git: 'git://github.com/nex3/sass.git', branch: 'master'

Gemfile.lock

GIT
  remote: git://github.com/nex3/sass.git
  revision: a6a80a8a594d9a1f904b931ff4facf88bc4908b4
  branch: master
  specs:
    sass (3.2.0.alpha.0)

GEM
  remote: http://rubygems.org/
  specs:
    fssm (0.2.7)

PLATFORMS
  ruby

DEPENDENCIES
  fssm
  sass!

gistfile1.sh

bundle exec sass --watch style.sass:style.css

style.css

body {
  background-color: #eeeeee; }

.page {
  width: 920px;
  background-color: white; }
  @media screen and (max-width: 320px) {
    .page {
      width: 100%; } }
  @media screen and (max-width: $px) {
    .page {
      width: 500px; } }

style.sass

=respond-to($media)
  @if $media == phone
    @media screen and (max-width: 320px)
      @content
  @if $media == tablet
    @media screen and (max-width: 768px)
      @content

=respond-max($px)
  @media screen and (max-width: $px)
    @content

body
  background-color: #eee

.page
  width: 920px
  background-color: #fff

  +respond-to(phone)
    width: 100%

  +respond-max(768px)
    width: 500px

Line 10 in style.sass is the problem. When you attempt to output a variable, sass passes it along without substituting the value. This happens whether you use interpolation or not.

Interpolation in media queries are not supported since 3.0.17 : http://sass-lang.com/docs/yardoc/file.SASS_CHANGELOG.html.
Since : sass/sass#217 it seems to be supported again (3.2.0).

This gist is using sass from master (3.2.0.alpha.0, commit: a6a80a8a59 from 29 November, after that pull request) and the interpolation isn't working. In 3.0.17, the changelog says that you would get an error instead of broken CSS, but the above gist shows that is no longer true in 3.2.0.alpha.

But its all cool. I chatted with @nex3 on IRC and he said this is simply not implemented yet, but will be.

Oops, I didn't read that pull request closely enough. That wasn't merged in at all, but @chriseppstein says an implementation is in the works.