type assertions affect the type narrowing of the subsequent code about typescript HOT 6 CLOSED

That's very strange. I'll take a look.

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This is a crash

This is no crash. Crash means the compiler crashes, not you receiving an error.

This changed between versions 5.3.3 and 5.3.4

You probably mean 5.4.3? There is no version 5.3.4.

Excuse my carelessness; I have made revisions.

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This is a crash

This is no crash. Crash means the compiler crashes, not you receiving an error.

This changed between versions 5.3.3 and 5.3.4

You probably mean 5.4.3? There is no version 5.3.4.

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crossref Will type assertions affect the type narrowing of the subsequent code?

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The issue here appears to be inconsistent caching of union and intersection property lookups, specifically the caching logic in getUnionOrIntersectionProperty and its handling of the skipObjectFunctionPropertyAugment parameter. It doesn't have anything to do with narrowing.

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I see what's happening. For various reasons we have two caches for resolved property lookups on unions and intersections, one that includes property augmentations from Object and Function, and one that doesn't. Logic was added in #54753 to propagate entries from the non-augmented cache to the augmented cache (see here), but that's incorrect when properties are marked with CheckFlags.Partial. I'll put up a PR with a fix.

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