Make IntEnum/StrEnum values passable to functions expecting literal ints or strs #19617
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
sterliakov
reviewed
Aug 8, 2025
| # This handles IntEnum, StrEnum, and custom (int, Enum) or (str, Enum) subclasses | ||
| if ( | ||
| left.is_enum_literal() | ||
| and isinstance(left.value, str) # Enum literal values are member names |
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Better make this assert inside the if body: we want a hard failure if enum literal somehow ended up with a non-string value
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| if isinstance(enum_type, Instance) and enum_type.last_known_value is not None: | ||
| # enum_type.last_known_value is the actual value for IntEnum/StrEnum | ||
| # members | ||
| if enum_type.last_known_value.value == self.right.value: | ||
| return True |
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Suggested change
| if isinstance(enum_type, Instance) and enum_type.last_known_value is not None: | |
| # enum_type.last_known_value is the actual value for IntEnum/StrEnum | |
| # members | |
| if enum_type.last_known_value.value == self.right.value: | |
| return True | |
| if isinstance(enum_type, Instance) and enum_type.last_known_value == self.right.value: | |
| # enum_type.last_known_value is the actual value for IntEnum/StrEnum | |
| # members | |
| return True |
Let's collapse the ladder?
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Ough, Eric raised a good point in the linked ticket. This is indeed unsafe, and probably |
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Fixes #19616.
Some design considerations:
MyIntEnum.ONEwhere aLiteral[1]is expected; this is becauseisinstance(MyIntEnum.ONE, int) == True.1would be passed where aMyIntEnumargument is expected: this is because two distinct enums that are semantically imcompatible might share numerical values. We want to emit errors if the user misuses an enum.