old_contents: 'use strict';
  
  const listSequences = require('./list-sequences');
  const shouldIgnoreRule = require('./should-ignore-rule');
  const shouldIgnoreSelector = require('./should-ignore-selector');
  const getSelectors = require('./get-selectors');
  
  /**
   * @param {Object} config
   * @param {Rule} config.rule - PostCSS Rule
   * @param {RegExp} config.utilityPattern
   * @param {RegExp} config.ignorePattern
   * @param {Result} config.result - PostCSS Result, for registering warnings
   */
  module.exports = config => {
    if (shouldIgnoreRule(config.rule)) return;
    const selectors = getSelectors(config.rule);
  
    selectors.forEach(selector => {
      const allSequences = listSequences(selector);
      let sequence;
      for (let i = 0, l = allSequences.length; i < l; i++) {
        sequence = allSequences[i];
        if (config.ignorePattern && shouldIgnoreSelector(sequence, config.ignorePattern)) continue;
        if (config.utilityPattern.test(sequence)) continue;
        config.result.warn(
          `Invalid utility selector "${selector}"`,
          {
            node: config.rule,
            word: selector,
          }
        );
        return;
      }
    });
  }
  
new_contents: 'use strict';
  
  const listSequences = require('./list-sequences');
  const shouldIgnoreRule = require('./should-ignore-rule');
  const shouldIgnoreSelector = require('./should-ignore-selector');
  const getSelectors = require('./get-selectors');
  
  /**
   * @param {Object} config
   * @param {Rule} config.rule - PostCSS Rule
   * @param {RegExp} config.utilityPattern
   * @param {RegExp} config.ignorePattern
   * @param {Result} config.result - PostCSS Result, for registering warnings
   */
  module.exports = config => {
    if (shouldIgnoreRule(config.rule)) return;
    const selectors = getSelectors(config.rule);
  
    selectors.forEach(selector => {
      const allSequences = listSequences(selector);
      for (const sequence of allSequences) {
        if (config.ignorePattern && shouldIgnoreSelector(sequence, config.ignorePattern)) continue;
        if (config.utilityPattern.test(sequence)) continue;
        config.result.warn(
          `Invalid utility selector "${selector}"`,
          {
            node: config.rule,
            word: selector,
          }
        );
        return;
      }
    });
  }
  
subject: Use for in loop