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Type guard does not work when its value is set to a variable. #19943
Description
TypeScript Version: 2.7.0-dev.20171111
Code
// -- Errors here:
test(value: number | undefined) : number {
let isNumber = typeof value == "number";
if (isNumber && value > 0) // < -- TS2532: Object is possibly 'undefined'.
return value * 10;
return 0;
}
// -- No errors here:
test(value: number | undefined) : number{
if (typeof value == "number" && value > 0)
return value * 10;
return 0;
}Expected behavior:
No errors
Actual behavior:
TS2532: Object is possibly 'undefined'.
Activity
ahejlsberg commentedon Nov 11, 2017
Duplicate of #12184.
typescript-bot commentedon Nov 27, 2017
Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.