Map over unions when getting iterated element type from contextual type #40592
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typescript-bot
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Author: Team
For Milestone Bug
weswigham
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Sep 16, 2020
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Fixes #40587
#40350 makes
Iterable<T> | undefinednon-iterable, which is correct on its face, but we failed to map over unions when looking at contextual types, soconst x: Iterable<1> | undefined = [1]was an error, because we were looking for the iteration types of the union (which has none) rather than looking at iteration types provided by each constituent in the union.