no-unused-vars is not right.

[PolanZ]

Tell us about your environment

• ESLint Version: v6.2.1
• Node Version: v10.16.0
• npm Version: 6.9.0

What parser (default, Babel-ESLint, etc.) are you using?
Babel-ESLint

Please show your full configuration:

module.exports = {
  root: true,
  env: {
    node: true
  },
  'extends': [
    'plugin:vue/essential',
    // '@smart/standard'
  ],
  // required to lint *.vue files
  plugins: [
    'vue'
  ],
  rules: {
    // allow async-await
    'max-len': [2, { 'code': 200 }],
    'space-before-function-paren': ['error', {
      'anonymous': 'always',
      'named': 'never',
      'asyncArrow': 'always'
    }],
    'no-multi-spaces': ['error', {
      'ignoreEOLComments': true
    }],
    'no-trailing-spaces': 'off',
    'no-unused-vars': [1, { 'args': 'none' }],
    'no-console': process.env.NODE_ENV === 'production' ? 'error' : 'off',
    'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off'
  },
  parserOptions: {
    parser: 'babel-eslint'
  }
};

Configuration

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.
lint

for (const key in sortType) {
  if (sortType[key].status === this.sortTypeStatus) {
    return sortType[key].name;
  }
}

What did you expect to happen?

'key' is defined but never used.eslint(no-unused-vars)

but! use in function rule is right. see

not output warning

[aladdin-add]

Duplicate of #12117

[aladdin-add]

please upgrade babel-eslint to resolve the issue.