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Click on a commit to change the comparison range[ty] Fix narrowing for transparent enums (StrEnum, IntEnum)
## Summary
This PR fixes incorrect type narrowing to Never for enums with transparent equality
semantics, such as StrEnum and IntEnum. These enums compare equal to their
underlying primitive values at runtime, but the type checker previously treated
them as disjoint.
The fix introduces a has_transparent_equality helper to identify enums inheriting
from primitive types (str, int, or bytes). It then updates disjointness checks and
intersection logic to recognize that these enum members are not disjoint from
matching primitive literals. This ensures that narrowing in match statements and
comparisons correctly preserves the appropriate types instead of collapsing to Never.
This directly resolves ty#1454 by improving the core type relation and builder
logic. By explicitly detecting transparent enums, this solution is more resilient
than relying on overrides_equality which is currently affected by pre-existing
lookup policy bugs.
Closes https://github.com/astral-sh/ty/issues/1454.
## Test Plan
I added a new test file match_enums.md with regression cases for:
- StrEnum narrowing in match statements.
- Handling of enums with custom __eq__ overrides (narrowing disabled).
- Tagged union narrowing with StrEnum in TypedDict fields.
I also verified that all existing enum and narrowing tests pass and that there
are no regressions in the semantic type checker's unit tests.