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Fix crash on ErasedType and covers_at_runtime #11924

Merged
merged 5 commits into from
Jan 7, 2022
Merged

Fix crash on ErasedType and covers_at_runtime #11924

merged 5 commits into from
Jan 7, 2022

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sobolevn
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@sobolevn sobolevn commented Jan 6, 2022

Closes #11913
Refs #11273
CC @hauntsaninja

mypy/subtypes.py Outdated
@@ -1167,6 +1167,14 @@ def restrict_subtype_away(t: Type, s: Type, *, ignore_promotions: bool = False)
def covers_at_runtime(item: Type, supertype: Type, ignore_promotions: bool) -> bool:
"""Will isinstance(item, supertype) always return True at runtime?"""
item = get_proper_type(item)
supertype = get_proper_type(supertype)
if (isinstance(item, (ErasedType, DeletedType))
or isinstance(supertype, (ErasedType, DeletedType))):
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Hmm I wonder if ErasedType instances can be nested inside unions, for example, and still cause a crash. Maybe erase_type should just propagate erased types unmodified? I don't think that DeletedType can be nested so it seems safe to handle here, though I'm not sure we need special casing for it. Did you find a use case where we encounter deleted types here, or is it here more as a defensive measure?

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@sobolevn sobolevn Jan 6, 2022

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Hm, good idea. I will try it!

Did you find a use case where we encounter deleted types here, or is it here more as a defensive measure?

More like a defensive programming. I will remove it, because it does not make much sense without ErasedType.

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Thanks for the updates!

@JukkaL JukkaL merged commit a0f27b1 into python:master Jan 7, 2022
JukkaL pushed a commit that referenced this pull request Jan 7, 2022
tushar-deepsource pushed a commit to DeepSourceCorp/mypy that referenced this pull request Jan 20, 2022
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INTERNAL ERROR RuntimeError in visit_erased_type with mypy 0.930
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