1322954 - Fix unsafe `instanceof` negations

Status: RESOLVED FIXED

(Toolkit :: General, defect)

Description

[Lina Butler (ex-Mozilla)]

Some of our modules use the pattern `!value instanceof Class`, to check if `value` is not an instance of `Class`.

This isn't quite right: `!` binds tighter than `instanceof`, so that will evaluate to `false instanceof Class`...which will always be false (https://github.com/DavidBruant/ECMAScript-regrets/issues/27).

We need an extra set of parens to make this work: `!(value instanceof Class)`.

Comment 1

[Lina Butler (ex-Mozilla)]

Attachment: Bug 1322954 - Fix incorrect `instanceof` negations.

Review commit: https://reviewboard.mozilla.org/r/98100/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/98100/

Comment 2

[Lina Butler (ex-Mozilla)]

Attachment: Bug 1322954 - Replace deprecated `no-negated-in-lhs` ESLint option with `no-unsafe-negation`.

Review commit: https://reviewboard.mozilla.org/r/98102/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/98102/

Comment 3

[Lina Butler (ex-Mozilla)]

Comment on attachment 8817933 [details]
Bug 1322954 - Replace deprecated `no-negated-in-lhs` ESLint option with `no-unsafe-negation`.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/98102/diff/1-2/

Comment 4

[Mark Hammond [:markh] [:mhammond]]

Comment on attachment 8817932 [details]
Bug 1322954 - Fix incorrect `instanceof` negations.

https://reviewboard.mozilla.org/r/98100/#review98410

wow - it's scary how often we weren't checking what we thought we were checking!

Comment 5

[Mark Hammond [:markh] [:mhammond]]

Comment on attachment 8817933 [details]
Bug 1322954 - Replace deprecated `no-negated-in-lhs` ESLint option with `no-unsafe-negation`.

https://reviewboard.mozilla.org/r/98102/#review98412

This looks great, but will require another try.

Comment 6

[Lina Butler (ex-Mozilla)]

Comment on attachment 8817932 [details]
Bug 1322954 - Fix incorrect `instanceof` negations.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/98100/diff/1-2/

Comment 7

[Lina Butler (ex-Mozilla)]

Comment on attachment 8817933 [details]
Bug 1322954 - Replace deprecated `no-negated-in-lhs` ESLint option with `no-unsafe-negation`.

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/98102/diff/2-3/

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4d6f11e28343
Fix incorrect `instanceof` negations. r=markh
https://hg.mozilla.org/integration/autoland/rev/2c1d9731a014
Replace deprecated `no-negated-in-lhs` ESLint option with `no-unsafe-negation`. r=markh

Comment 9

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/4d6f11e28343
https://hg.mozilla.org/mozilla-central/rev/2c1d9731a014