Change typeof narrowing to narrow selected union members
#25243
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| @@ -367,15 +367,15 @@ function test14(a: boolean | number | void) { | |||
| if (typeof a === "boolean") { | |||
| >typeof a === "boolean" : boolean | |||
| >typeof a : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function" | |||
| >a : number | boolean | void | |||
| >a : undefined | |||
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This is kind of a scary diff - is there an observable breaking change we need to document?
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a started as boolean | number | void - it then for narrowed against undefined (which actually matches the void case - and void & undefined is apparently just undefined). Previously we just missed that narrowing opportunity. And naturally, undefined narrowed by boolean simply becomes never below, like one would hope!
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Reviewer advice: Review with the ignore whitespace box checked. |
RyanCavanaugh
approved these changes
Sep 6, 2018
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And to intersect even in the subtype case so
keyof Tnarrows tokeyof T & stringand notstring.Fixes #25179