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Optional chaining control flow refinements missing #34570

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ahejlsberg opened this issue Oct 18, 2019 · 0 comments · Fixed by #34597
Closed

Optional chaining control flow refinements missing #34570

ahejlsberg opened this issue Oct 18, 2019 · 0 comments · Fixed by #34597
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@ahejlsberg
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Bug A bug in TypeScript Fix Available A PR has been opened for this issue
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TypeScript 3.7.1

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@ahejlsberg
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TypeScript Version: 3.7.x-dev.20191017

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In the comments on #33736, several issues related to control flow analysis of optional chaining constructs are mentioned. Specifically:

#33736 (comment) -- No narrowing in switch statement.
#33736 (comment) -- No narrowing following assertion.
#33736 (comment) -- No narrowing in false branch of if statement.

Expected behavior:

Proper narrowing as indicated in the examples.

Actual behavior:

No narrowing.
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More optional chaining control flow analysis microsoft/TypeScript
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