feat: TypeScript 5.4 support for svelte-check

[jasonlyu123]

Auto import seems to be broken. Need to check what the problem is. We also need to check if the Preserved Narrowing in Closures Following Last Assignments changes the narrowing in any unexpected ways (#2316).

Auto Import in non-ts svelte file has some regression in 5.4. So this only adds the support for svelte-check. Editor support waiting on if the upstream fix is merged. So 5.4 might be skipped.

[jasonlyu123]

Seems like auto-import is broken in js/non-ts-svelte files importing export default from ts/ts-svelte files. And also declare function like onMount in svelte 3.

[dummdidumm]

Is this reproducible without Svelte? i.e. import a export default of a .ts file inside a .js file doesn't work? If so, we should open a bug report in the TypeScript repo.

[jasonlyu123]

Yeah. it also happens in js files. Also found that the problem with onMount in svelte 3 isn't because it has a declare modifier. It's because of the barrel export. Barrel export seems like a way bigger problem than the default export. Upstream issue microsoft/TypeScript#57740

[jasonlyu123]

Let's wait until VSCode releases with TypeScript 5.4 to see if enough people complain about it and see if the fix can made into a 5.4 patch release. If not, we can probably either

1. Adjust the test and add a dedicated test for auto-import reexport/default export. Skipped it and enabled it when the fix was released.
2. Pin the version in 5.3 but release the fixes with binding control flow and transition type-check.

[dummdidumm]

The bug was put into the backlog, it doesn't look like it has any priority. We may have to dig into the code base ourselves and make a TS pull request. Would you be willing to try that?
In the meantime doing option 2 sounds good (in fact I already pinned it because I had to release a fix)

[DePasqualeOrg]

It looks like the TypeScript version in the svelte-check package still needs to be updated. I'm getting errors when running svelte-check that don't appear in VS Code, where I'm running the latest TypeScript.