Bugs in negated in expressions

[gorosgobe]

What version of Bun is running?

No response

What platform is your computer?

No response

What steps can reproduce the bug?

in and instanceof expressions in JS

a in obj;
a instanceof C;

can be negated by grouping them and applying the ! operator, i.e.

!(a in obj);
!(a instanceof C);

Applying the ! operator incorrectly (on the LHS operand) leads to bugs:

!a in obj; // will evaluate to false, unless obj has a "true" or "false" key
!a instanceof C; // will evaluate to false, unless C overrides instanceof with a @@hasInstance method

For more information, please see these MDN docs and the no-unsafe-negation recommended Eslint rule.

I have found a potentially problematic instance of the above bugs in your codebase:

bun/test/js/node/process/process.test.js

Line 106 in 5d09a06

if (!"TZ" in process.env) {

What is the expected behavior?

No response

What do you see instead?

No response

Additional information

No response