Suggest making a protocol member read-only on invariance conflict#21723
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apoorva-01 wants to merge 1 commit into
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Suggest making a protocol member read-only on invariance conflict#21723apoorva-01 wants to merge 1 commit into
apoorva-01 wants to merge 1 commit into
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When a mutable protocol attribute is rejected only because it's invariant and the concrete type is narrower, point at making it read-only, like the existing covariant-collection note. Fixes python#6002.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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Fixes #6002
A mutable protocol attr with a narrower concrete type only fails because of invariance, but the error never says that. Adds a note right after "expected X, got Y":
Only when read-only would actually fix it, so a real int/str mismatch stays quiet. Same idea as the covariant-collection note, plus the docs link ilevkivskyi wanted.