src/node_modules/clean-css/lib/optimizer/level-2/rules-overlap.js

var MODIFIER_PATTERN = /--.+$/;

function rulesOverlap(rule1, rule2, bemMode) {
  var scope1;
  var scope2;
  var i, l;
  var j, m;

  for (i = 0, l = rule1.length; i < l; i++) {
    scope1 = rule1[i][1];

    for (j = 0, m = rule2.length; j < m; j++) {
      scope2 = rule2[j][1];

      if (scope1 == scope2) {
        return true;
      }

      if (bemMode && withoutModifiers(scope1) == withoutModifiers(scope2)) {
        return true;
      }
    }
  }

  return false;
}

function withoutModifiers(scope) {
  return scope.replace(MODIFIER_PATTERN, '');
}

module.exports = rulesOverlap;