types overlap only if all type args match #9452
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gvanrossum
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Sep 17, 2020
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| # Or, to use a more concrete example, List[Union[A, B]] and List[Union[B, C]] | ||
| # would be considered partially overlapping since it's possible for both lists | ||
| # to contain only instances of B at runtime. |
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Looking at this example I am wondering if the original behavior wasn't intentional?
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The example only has a single type argument; I think the case with multiple args was just not considered.
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I stumbled a little on this too, unions are dealt with by the recursive call, about a hundred lines earlier in the function
JukkaL
approved these changes
Sep 18, 2020
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Fixes #9451
Description
Previously, generic types were considered overlapping as soon as the first type argument matched. Now, we check all type arguments.
Test Plan
The new test failed before my change and now passes.