False positive for no-unused-vars when first argument in an array of arguments is unused

Tell us about your environment

• ESLint Version: 3.12.2
• Node Version: 7.3.0
• npm Version: 4.0.5

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

Please show your full configuration:

root: true
extends: airbnb-base

What did you do? Please include the actual source code causing the issue.

module.exports = (baz, [foo, bar]) => {
  console.log(bar);
};

What did you expect to happen?

I expected foo not to be marked as an unused variable, because it pads bar. Removing foo would alter the behaviour of the code.

What actually happened? Please include the actual, raw output from ESLint.

foo got marked as an unused variable.

$ ./node_modules/.bin/eslint example.js 

/home/remco/d-centralize/appsemble-components/appsemble-build/example.js
  1:25  error    'foo' is defined but never used  no-unused-vars
  2:3   warning  Unexpected console statement     no-console

✖ 2 problems (1 error, 1 warning)

[remcohaszing]

@vitorbal I wasn’t aware this syntax exists, but it makes sense.

Perhaps this could be added as an example to the documentation.

[vitorbal]

Given you could do something like the following, I’m not entirely sure this should be considered a bug or not:

module.exports = (baz, [, bar]) => {
  console.log(bar);
};