I figured it out
someone (not me) added typescript to the project’s dependencies
other tooling picked up on that and *without any configuration changes* started applying typescript rules to javascript files,
typescript, being a cop, and a bad one at that, takes `const foo = [3]` to mean `number[]` and not `Array<number>` which… are somehow different in typescript land?
and typescript the cop doesn’t let this pass muster
look, JavaScript is bad but IMO TypeScript only makes it worse