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Can not infer not null / undefined when use enum as the optional key #30714
Description
TypeScript Version: 3.4.0-dev.201xxxxx
Search Terms:
enum as key
Code
enum A {
a,
b,
c
}
type b = A.a|A.b
const a: {
[key in A]?: {
[key in A]?: string
}
} = {
[A.a]: {
[A.a]: "a"
}
}
function t() {
// below line will have error on a[A.a][A.a] for possibly `undefined` when enabled `strictNullChecks`
if (a[A.a] && a[A.a][A.a]) {
return a[A.a][A.a];
}
return
}Expected behavior:
no err when enable strictNullChecks, as the undefined should be ruled out after first a[A.a] check.
Actual behavior:
Object is possibly 'undefined'. for a[A.a][A.a]
Activity
RyanCavanaugh commentedon Apr 2, 2019
Duplicate #28081
typescript-bot commentedon Apr 5, 2019
This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.
jcalz commentedon Dec 23, 2019
The fix for #28081, namely #31478, did not address enum keys; should this be reopened or should a new issue be filed?