Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// ----
$ru: (
  name: 'ru',
  font-size: 12px,
  font-family: "Helvetica",
  letter-spacing: 1px
);

$cn: (
  name:'cn',
  font-size:12px,
  font-family:"Times Roman",
  letter-spacing:-1px
);

@mixin test ($list){
  html[lang=#{map-get(nth($list, 1),name)}] & {
    font-size: map-get(nth($list, 1), font-size);
  }
}

.bygph {
  @include test( ($ru, $cn) );
}

SassMeister-output.css

html[lang=ru] .bygph {
  font-size: 12px;
}