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Type guard not working in returned function #12616
Description
TypeScript Version: 2.2.0-dev.20161202
Code
function getGetter() {
let data = {}
data['bar'] = 1
if (hasBar(data)) {
return () => data.bar // Property 'bar' does not exist on type '{}'.
}
}
function hasBar(thing): thing is {bar: number} {
return typeof thing.bar == 'number'
}Expected behavior:
Compile successfully.
Actual behavior:
index.ts(6,21): error TS2339: Property 'bar' does not exist on type '{}'.
Activity
ahejlsberg commentedon Dec 3, 2016
Your example works if you use
constto declaredata. Type guards forletvariables are not in effect in nested functions because the variable might be reassigned. See #8849.andraaspar commentedon Dec 3, 2016
I see. You are right.