Self-check is failing because of this change.

@typescript-bot cherry-pick this to release-5.4

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Hey, @RyanCavanaugh! I was unable to cherry-pick this PR.

Check the logs at: https://github.com/microsoft/TypeScript/actions/runs/8254939580

This will need to be manually cherry-picked; not sure if someone's done that already.

But in the future, we might come up with a fix for the underlying problem and we can then bring this change back.

Is there any chance that this fix happens before the next patch release of 5.4? It's somewhat thrashy to have to migrate code back and forth especially between just patch versions.

• TS 5.4 comes out

switch
...
default:
-  assertNever(foo.type);  // foo is never now so this isn't allowed
+  assertNever(foo);

• This PR gets is released

switch
...
default:
-  assertNever(foo);
+  assertNever(foo.type);  // have to change it back

• Future fix

switch
...
default:
-  assertNever(foo.type);
+  assertNever(foo);  // have to change it back again

No, a future fix would be in 5.5 or later, hence the nebulous "in the future, we might come up with a fix". We typically just revert anything that is nontrivial to fix for patch releases. I guess that's "thrashy", but TS 5.4's only been out for two weeks and reverting this is safest.

This will need to be manually cherry-picked; not sure if someone's done that already.

It looks like this revert was not included in v5.4.3 that was just released. Will this revert be included in the next patch release?

This was definitely included in 5.4.3: #57795