No union subtype reduction during type inference #37327
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weswigham
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Mar 10, 2020
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@typescript-bot run dt |
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Heya @ahejlsberg, I've started to run the extended test suite on this PR at ef03050. You can monitor the build here. |
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Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at ef03050. You can monitor the build here. |
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Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at ef03050. You can monitor the build here. |
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The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master. |
orta
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Mar 10, 2020
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Looks good, thanks for looking into it!
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@ahejlsberg thanks a lot 🙏 |
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One thing that immediately stands out in the stack trace for #31230 is that we're performing subtype reduction (
removeSubtypes) on a union type during inference. We shouldn't be doing that, at least not without recursion limiters in place, because subtype reduction checks relations, which may perform inference, and off we go. It appears that removing theUnionReduction.Subtypeflag where we construct a union type ingetImplicitIndexTypeOfTypefixes the issue.Fixes #31230.