Allow non-generic return types to be read from single generic call signatures #54477
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Andarist
commented
May 31, 2023
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| // @strict: true | |||
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test case reduced from https://github.com/Thinkmill/graphql-ts
interestingly, this one also depends on a quite recent change from #53246
Andarist
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May 31, 2023
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| declare function fn2<T>(): (cb: () => any) => (a: T) => void; | ||
| const res2 = fn2()(() => res2); | ||
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| declare function fn3<T>(): <T2>(cb: (arg: T2) => any) => (a: T) => void; | ||
| const res3 = fn3()(() => res3); |
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The only diff between those 2 is the T2 type parameter. The fn2 case works today but the fn3 doesn't - even though its return type doesn't actually depend on T2.
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How does fn3 fail? It looks like inference still fails, given that res3: (a: unknown) => void -- but I'm not sure, and I don't see how to observe what's inferred for T2. Maybe the return type of fn3 should be (a: T) => T2 in the test?
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How does fn3 fail?
We end up with: "'res3' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer.(7022)"
It looks like inference still fails, given that res3: (a: unknown) => void
It doesn't exactly fail, it's just that there are no inference candidates here so the constraint is used and that's unknown. This isn't meant to be used as a compelling use case for this PR, just a super minimal repro. The better motivating example is showcased in circularReferenceInReturnType2.ts.
I don't see how to observe what's inferred for T2.
It's just unknown. I re-checked this with console.log(typeToString(inference.typeParameter), typeToString(inference.inferredType)) before exiting getInferredType.
Maybe the return type of fn3 should be (a: T) => T2 in the test?
That's not good here because that reintroduces the circularity because the return type starts to depend on a type parameter again.
…pes-avoid-circularity
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@typescript-bot test this |
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Heya @sandersn, I've started to run the diff-based user code test suite (tsserver) on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Heya @sandersn, I've started to run the perf test suite on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Heya @sandersn, I've started to run the diff-based user code test suite on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Heya @sandersn, I've started to run the diff-based top-repos suite (tsserver) on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Heya @sandersn, I've started to run the diff-based top-repos suite on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Heya @sandersn, I've started to run the parallelized Definitely Typed test suite on this PR at 3b17f59. You can monitor the build here. Update: The results are in! |
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Hey @sandersn, I've packed this into an installable tgz. You can install it for testing by referencing it in your and then running There is also a playground for this build and an npm module you can use via |
sandersn
requested changes
Jun 19, 2023
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| declare function fn2<T>(): (cb: () => any) => (a: T) => void; | ||
| const res2 = fn2()(() => res2); | ||
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| declare function fn3<T>(): <T2>(cb: (arg: T2) => any) => (a: T) => void; | ||
| const res3 = fn3()(() => res3); |
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How does fn3 fail? It looks like inference still fails, given that res3: (a: unknown) => void -- but I'm not sure, and I don't see how to observe what's inferred for T2. Maybe the return type of fn3 should be (a: T) => T2 in the test?
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@sandersn Here are the results of running the user test suite comparing There were infrastructure failures potentially unrelated to your change:
Otherwise... Something interesting changed - please have a look. Details
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@sandersn Here are the results of running the user test suite comparing Everything looks good! |
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@sandersn Here they are:
CompilerComparison Report - main..54477
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TSServerComparison Report - main..54477
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StartupComparison Report - main..54477
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Developer Information: |
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Hey @sandersn, the results of running the DT tests are ready. |
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@sandersn Here are the results of running the top-repos suite comparing Everything looks good! |
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@sandersn Here are the results of running the top-repos suite comparing Everything looks good! |
sandersn
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Jul 6, 2023
sandersn
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Jan 24, 2024
Discovered in microsoft#57117 The implementation should not `couldContainTypeVariables`--it's not intended a fast path, and should not be used in places where its unreliability can be observed. The tests stay, but with a note added that they should pass but do not.
DanielRosenwasser
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Jan 25, 2024
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This PR permits circular references in some return types of generic call signatures - something that is already allowed in non-generic call signatures.
If the return type doesn't depend on type variables then the same thing can be allowed for it (including cases with instantiated return types not depending on type variables).