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Strict Comparison Operator Doesn't Infer Singleton Types Correctly #6940

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Volodymyr Shatskyi (vlad-shatskyi)

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Having a singleton type type A = "a" | "b", a variable const a: A = "a", and an expression a === "c", the compiler should infer the type of "c" as A and make the expression unsound.

Currently (1.8.0 and 1.9.0-dev.20160206) it compiles, which makes usage of singleton types instead of enums less type safe.

Ryan Cavanaugh (RyanCavanaugh)
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SuggestionAn idea for TypeScript

In DiscussionNot yet reached consensus
on Feb 6, 2016
RyanCavanaugh commented on Feb 6, 2016
Ryan Cavanaugh (RyanCavanaugh)
on Feb 6, 2016
Member
This is a good idea
weswigham commented on Feb 8, 2016
Wesley Wigham (weswigham)
on Feb 8, 2016
Member
#6196 should fix this, right?
vlad-shatskyi commented on Feb 8, 2016
Volodymyr Shatskyi (vlad-shatskyi)
on Feb 8, 2016
Author
Yes, Wesley Wigham (@weswigham). Closing this issue.
Volodymyr Shatskyi (vlad-shatskyi)
closed this as completed on Feb 8, 2016
Ryan Cavanaugh (RyanCavanaugh)
added
DuplicateAn existing issue was already created
and removed
In DiscussionNot yet reached consensus

SuggestionAn idea for TypeScript
on Feb 8, 2016
microsoft
locked and limited conversation to collaborators on Jun 19, 2018

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