[ty] Fix match pattern value narrowing to use equality semantics #20882
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ericmarkmartin
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AlexWaygood,
carljm,
dcreager and
sharkdp
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Diagnostic diff on typing conformance testsNo changes detected when running ty on typing conformance tests ✅ |
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AlexWaygood
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sharkdp
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Oct 15, 2025
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Thank you very much. It would be great if we could update some of the old tests in order to restore the original intention. Otherwise, this looks great.
sharkdp
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Oct 16, 2025
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Thank you for the update
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Oct 16, 2025
…rable * origin/main: Don't use codspeed or depot runners in CI jobs on forks (#20894) [ty] cache Type::is_redundant_with (#20477) Fix run-away for mutually referential instance attributes (#20645) [ty] Limit shown import paths to at most 5 unless ty runs with `-v` (#20912) [ty] Use field-specifier return type as the default type for the field (#20915) [ty] Do not assume that `field`s have a default value (#20914) [ty] Fix match pattern value narrowing to use equality semantics (#20882) Update setup instructions for Zed 0.208.0+ (#20902) Move TOML indent size config (#20905) [syntax-errors]: implement F702 as semantic syntax error (#20869) [ty] Heterogeneous unpacking support for unions (#20377) [ty] refactor `Place` (#20871) Auto-accept snapshot changes as part of typeshed-sync PRs (#20892) [`airflow`] Add warning to `airflow.datasets.DatasetEvent` usage (`AIR301`) (#20551) [`flake8-pyi`] Fix operator precedence by adding parentheses when needed (`PYI061`) (#20508) [`pyupgrade`] Fix false negative for `TypeVar` with default argument in `non-pep695-generic-class` (`UP046`) (#20660) Update parser snapshots (#20893) Fix syntax error false positives for escapes and quotes in f-strings (#20867)
dcreager
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Oct 16, 2025
…nt-sets * dcreager/non-non-inferable: Don't use codspeed or depot runners in CI jobs on forks (#20894) [ty] cache Type::is_redundant_with (#20477) Fix run-away for mutually referential instance attributes (#20645) [ty] Limit shown import paths to at most 5 unless ty runs with `-v` (#20912) [ty] Use field-specifier return type as the default type for the field (#20915) [ty] Do not assume that `field`s have a default value (#20914) [ty] Fix match pattern value narrowing to use equality semantics (#20882) Update setup instructions for Zed 0.208.0+ (#20902) Move TOML indent size config (#20905) [syntax-errors]: implement F702 as semantic syntax error (#20869) [ty] Heterogeneous unpacking support for unions (#20377) [ty] refactor `Place` (#20871) Auto-accept snapshot changes as part of typeshed-sync PRs (#20892) [`airflow`] Add warning to `airflow.datasets.DatasetEvent` usage (`AIR301`) (#20551) [`flake8-pyi`] Fix operator precedence by adding parentheses when needed (`PYI061`) (#20508) [`pyupgrade`] Fix false negative for `TypeVar` with default argument in `non-pep695-generic-class` (`UP046`) (#20660) Update parser snapshots (#20893) Fix syntax error false positives for escapes and quotes in f-strings (#20867)
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Summary
Resolves astral-sh/ty#1349.
Fix match statement value patterns to use equality comparison semantics instead of incorrectly narrowing to literal types directly. Value patterns use equality for matching, and equality can be overridden, so we can't always narrow to the matched literal.
Test Plan
Updated match.md with corrected expected types and an additional example with explanation