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Fix typing of the Observable<boolean> #168
Description
See:
- Need to fix Typescript definitions since Typescript 4.6 knockout#2589
- Type 'X<false>' is not assignable to type 'X<boolean>'. microsoft/TypeScript#48150
// Broken
function observable<T>(value: T): Observable<T>
{
return undefined as any; // the implementation is not important
}
// Fixed
function observable<T>(value: T extends infer U ? U: never): Observable<T>
{
return undefined as any; // the implementation is not important
}
Activity
maskmaster commentedon Mar 8, 2022
I added an answer in the stackoverflow question. We need to make sure that these two lines remain valid after any fix.
tomhanax commentedon Mar 8, 2022
For now the best I can offer is:
The playground contains many examples and seems OK, of course anybody can check and correct if needed, I am no expert in this.
Playground Link
brianmhunt commentedon Mar 8, 2022
Thanks @maskmaster , @tomhanax the answer & playground are very helpful.
direct link to the SO question
chuanqisun commentedon May 20, 2022
Hi, I believe I'm hitting the same issue when upgrading to typescript 4.6 but I might need some help understanding the workaround. Here is a minimum repro.
The
ExtendedTypeis clearly assignable to theBaseType, but typescript wouldn't allow. Also, the error suggests that typescript is trying to assignBaseTypetoExtendedType, which is opposite to the desired direction.Should I manually patch the type definitely of
KnockoutObservable? I'm not sure how that might work. Thank you and let me know if I should cross post to other repos.mbest commentedon Jul 15, 2022
This was fixed in TypeScript: microsoft/TypeScript#48380
phillipc commentedon Nov 22, 2025
We have corrected all the TKO typings in #202. Specifically, this case with a newer version of TypeScript.