Inconsistent tsc behavior on TS 5.4

[olegafx]

Inconsistent tsc behavior on TS 5.4

[RyanCavanaugh]

There's really not much we can do without a way to reproduce the problem, unfortunately

[olegafx]

Ok, I was able to reproduce it. Here is a link to StackBlitz. There are 2 main cases:

1. If you'll open fail.tsx, you won't see any errors in the editor. But if you will run yarn tsc --noEmit in the terminal, you'll see src/fail/fail.tsx:18:22 - error TS2322: Type 'unknown[]' is not assignable to type 'FailedItem[]'.
2. Start tsc in watch mode: yarn tsc --noEmit --watch. Open fail.tsx and add // @ts-expect-error in any place of the code. Remove this comment. It will show 0 errors in the console.

Also you could notice that there is import '@total-typescript/ts-reset/is-array'; in reset.d.ts. The only thing it's doing is changing any to unknown for Array.isArray. Source code.

React version doesn't really matter. It works the same on v16 and v18.

[DanielRosenwasser]

For what it's worth, the only thing that was merged in between those dates was #57122