(🎁) conformance: check for variance on constrained type variables #2016
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KotlinIsland
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erictraut
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May 28, 2025
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I don't think this proposed test is correct. I also can't find where it's specified in the typing spec.
| # reveal_type(concat(m, a)) | ||
| # reveal_type(concat(a, m)) | ||
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| BadConstraint3 = TypeVar("BadConstraint3", str, int, covariant=True) # E: constraints can't have variance |
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I can't find where in the typing spec this is specified. I'm also not sure why it would be the case that value-constrained type variables can't be covariant.
In any case, all conformance tests should derive from the spec itself. You'll see that in most of the tests, the exact text of the spec is quoted to motivate each of the tests.
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Note that variance is meaningful on constrained type variables if one constraint is assignable to the other. (Given a |
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i can't update the results on my machine, sorry!