no-unused-vars false positive after upgrading to v3.0.0

[gustavohenke]

What version of ESLint are you using?
3.0.0

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

Please show your full configuration:

{
    "root": true,
    "env": {
        "browser": true,
        "es6": true,
        "amd": true,
        "jquery": true
    },
    "globals": {
        "_": false,
        "angular": false,
        "CKEDITOR": false,
        "google": false
    },
    "parserOptions": {
        "ecmaVersion": 6
    },
    "rules": {
        // Possible errors
        "no-dupe-keys":                  2,
        "no-empty":                      1,
        "no-ex-assign":                  1,
        "no-irregular-whitespace":       2,

        // Best practices
        "curly":                       [ 2, "all" ],
        "dot-notation":                [ 2, {
            "allowKeywords": true
        }],
        "dot-location":                [ 2, "property" ],
        "eqeqeq":                      [ 2, "allow-null" ],
        "guard-for-in":                  1,
        "no-else-return":                1,
        "no-labels":                     2,
        "no-extend-native":              2,
        "no-fallthrough":                0,
        "no-lone-blocks":                1,
        "no-loop-func":                  2,
        "no-multi-spaces":               0,
        "no-multi-str":                  2,
        "no-native-reassign":            2,
        "no-param-reassign":             0,
        "no-return-assign":              0,
        "no-unused-expressions":         0,
        "radix":                         1,
        "yoda":                          2,

        // Variables
        "no-undef":                      2,
        "no-unused-vars":                2,
        "no-use-before-define":        [ 2, "nofunc" ],

        // Stylistic issues
        "array-bracket-spacing":       [ 2, "always", {
            "objectsInArrays": false
        }],
        "brace-style":                 [ 2, "1tbs", {
            "allowSingleLine": true
        }],
        "camelcase":                   [ 2, {
            "properties": "never"
        }],
        "comma-spacing":                 2,
        "comma-style":                   2,
        "computed-property-spacing":   [ 2, "always" ],
        "eol-last":                      0,
        "indent":                      [ 2, "tab", {
            "SwitchCase": 1
        }],
        "key-spacing":                   0,
        "lines-around-comment":        [ 2, {
            "allowBlockStart": true
        }],
        "max-nested-callbacks":        [ 1, 5 ],
        "new-parens":                    2,
        "newline-after-var":             0,
        "no-spaced-func":                0,
        "object-curly-spacing":        [ 2, "always" ],
        "one-var":                     [ 2, {
            "initialized":   "never"
        }],
        "quotes":                      [ 2, "double" ],
        "keyword-spacing":             [ 2, {
            "before": true,
            "after": true
        }],
        "space-in-parens":               0,
        "space-infix-ops":               2,
        "space-unary-ops":             [ 2, {
            "words": true,
            "nonwords": false
        }],
        "spaced-comment":              [ 2, "always" ],

        // Legacy
        "max-len":                     [ 2, 150 ]
    }
}

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

var unregisterFooWatcher;
// ...
unregisterFooWatcher = $scope.$watch( "foo", function( foo ) {
    // ...some code..
    unregisterFooWatcher();
});

What did you expect to happen?
Code linted just fine.

What actually happened?

/path/to/file.js
  29:8  error  'unregisterFooWatcher' is defined but never used  no-unused-vars

Seems to be caused by modifications of #6348 and #6535.

[gustavohenke]

To be clear, our builds started failing a few hours ago because we run npm install -g eslint (no version specified).

For now, I'll just specify version 2..

[nzakas]

cc @mysticatea

[mysticatea]

Ugh, I'm sorry.
I will fix it.

[doberkofler]

@mysticatea Is this the same false positive I found in eslint 3.0.0 ?

/*eslint no-unused-vars:2*/
let _timer;
function f() {
    _timer = setTimeout(function () {}, _timer ? 100 : 0);
}
f();

reports:

3:5  warning  '_timer' is defined but never used  no-unused-vars

[yphoenix]

This looks like the same bug I'm seeing with:

function foo(){
    'use strict';

    var ref;

    ref = setInterval(
        function(){
            clearInterval(ref);
        }, 10);
}

As soon as I upgraded to 3.0.0

[mysticatea]

@doberkofler Thank you for the repro code. I added a check to address that pattern to no-unused-vars.
@yphoenix Thank you for the repro code. Yes, it's the same bug. I added the code to tests.