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Allow Boolean() to be used to perform a null check #29955
Allow Boolean() to be used to perform a null check #29955
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Hi, this is a really good initiative, do you think we can skip specifying generic after this |
@typescript-bot test this |
Heya @RyanCavanaugh, I've started to run the extended test suite on this PR at 24e7e1c. You can monitor the build here. It should now contribute to this PR's status checks. |
@beshanoe I think that may be sufficient to allow us to skip specifying generic parameters. I'm not sure though without testing it. I found: function B<T>(value: T): value is Exclude<T, false | null | undefined | '' | 0> {
return Boolean(value);
} was already sufficient, but adding prototypes/new functions to the interface forces you to be explicit. |
@ForbesLindesay can you merge this up with master? This will allow us to re-run the RWC suite to evaluate the effects of this on our real-world code database |
… boolean-null-check
@RyanCavanaugh sorry I didn't see your message. I've merged it now. |
@RyanCavanaugh any update on this? |
@typescript-bot test this |
Heya @RyanCavanaugh, I've started to run the extended test suite on this PR at 37bb42c. You can monitor the build here. It should now contribute to this PR's status checks. |
RWC is actually clean, ignore ❌ |
@RyanCavanaugh any chance we can merge this? It's been a while and it's a very simple fix. |
☝️ 🙏 |
Resolves #31164. |
broken by #31515 |
This would be a great addition to the language. Have there been any plans on when it might land? 3.8 maybe? |
Can we revive this. Still continues to prevent usage of the .filter(Boolean) syntax sugar today. |
Check out ts-reset. |
Is there a good workaround in the meantime? I'm not sure how else to express |
You can use type guards: ["", undefined, "test"].filter((x): x is string => typeof x === "string") |
Works universally for any |
The code in #29955 (comment) more completely shows the result of |
Fixes #16655
This allows code like:
to be written and to typecheck. Unfortunately the generic type still has to be specified, otherwise TypeScript picks the other, less specific overload of
.filter
.