Add tests for inferring contextual generic mapped types #52709
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Andarist
commented
Feb 9, 2023
| // @strict: true | ||
| // @noEmit: true | ||
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| type LowInfer<T> = T & {}; |
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Since those tests are using LowInfer - cc @RyanCavanaugh who was mentioning this as a somewhat viable and stable pattern in some of the issues
Andarist
commented
Feb 9, 2023
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| interface AssignAction<TContext> { | ||
| type: "xstate.assign"; | ||
| exec: (arg: TContext, meta: Meta<TContext>) => void; |
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The only difference between those 2 tests is that this one is using a property with a function value here and the other one is using a callable signature. Both cases are somewhat important for us in XState.
Andarist
commented
Feb 9, 2023
| @@ -0,0 +1,41 @@ | |||
| // @strict: true | |||
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You can play around with those test cases in the TS 4.7 playground where they error.
sandersn
approved these changes
Mar 3, 2023
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This PR only introduces some tests. We started relying on this in XState and it turned out that this doesn't work pre-4.8.
I tracked down the PR that enabled this use case: #49696 (cc @ahejlsberg ). It wasn't fixing any case like that (no similar tests introduced there) so I figured out that it's best for us to provide tests for this here - to ensure that this won't accidentally regress (as long as you believe that this should continue to work, of course)