Sourced from ty's releases.

0.0.19

Release Notes

Released on 2026-02-26.

Bug fixes

• Fix panic in diagnostic rendering when attempting to render a code frame pointing to leading whitespace (#23458)
• Fix panics and incorrect inference stemming from incorrectly considering overloads in another file as being associated with a function in the file being checked (#21977)
• Fix panic when attempting to narrow the type of a dictionary key that was assigned using a multi-target assignment, e.g. x = y = {"a": 1} (#23523)
• Fix infinite hang on mutually recursive TypeAliasType definitions (#23397)

LSP server

• Fix inlay hints for starred unpacking targets (#23454)

Core type checking

• Fix assignability, subtyping and equivalence checks relating to typing.Generator prior to Python 3.13 (#23386)
• Understand that a scope's control flow terminates after await foo() if foo returns typing.Awaitable[typing.Never] or similar (#23479)
• Implement stricter handling of calls to instances of type[T] types (#23472)
• Support basic type narrowing for case {...}: patterns in match statements (#23462)
• Fix bugs that could manifest in incorrect overload evaluation, false-positive complaints regarding assert_type calls or false-positive redundant-cast diagnostics by reimplementing the equivalence type relation as mutual subtyping of top and bottom materializations (#23428)
• Fix equality and __contains__ narrowing with PEP-695 type aliases (#23545)
• Support _value_ annotations on enum classes (#22228)

Improvements to diagnostics

• Improve diagnostics when attempting to specialize non-generic types (#23516)
• Render subdiagnostics when --output-format=github is specified (#23455)

Performance

• Add a cached method for calculating the intersection of two types (#23547)
• Add a cached method for calculating the union of two types (#23565)
• Reduce the threshold above which Literal types in unions are upcasted to nominal-instance types in situations where the union type is recursively defined (#23521)
• Control flow: isolate the calculation of "loop header reachability" in a dedicated, cached function (#23520)

Contributors

• @​AlexWaygood
• @​silamon
• @​ibraheemdev
• @​Hugo-Polloli
• @​charliermarsh
• @​knutwannheden
• @​oconnor663
• @​carljm
• @​mtshiba

... (truncated)

Sourced from ty's changelog.

0.0.19

Released on 2026-02-26.

Bug fixes

• Fix panic in diagnostic rendering when attempting to render a code frame pointing to leading whitespace (#23458)
• Fix panics and incorrect inference stemming from incorrectly considering overloads in another file as being associated with a function in the file being checked (#21977)
• Fix panic when attempting to narrow the type of a dictionary key that was assigned using a multi-target assignment, e.g. x = y = {"a": 1} (#23523)
• Fix infinite hang on mutually recursive TypeAliasType definitions (#23397)

LSP server

• Fix inlay hints for starred unpacking targets (#23454)

Core type checking

• Fix assignability, subtyping and equivalence checks relating to typing.Generator prior to Python 3.13 (#23386)
• Understand that a scope's control flow terminates after await foo() if foo returns typing.Awaitable[typing.Never] or similar (#23479)
• Implement stricter handling of calls to instances of type[T] types (#23472)
• Support basic type narrowing for case {...}: patterns in match statements (#23462)
• Fix bugs that could manifest in incorrect overload evaluation, false-positive complaints regarding assert_type calls or false-positive redundant-cast diagnostics by reimplementing the equivalence type relation as mutual subtyping of top and bottom materializations (#23428)
• Fix equality and __contains__ narrowing with PEP-695 type aliases (#23545)
• Support _value_ annotations on enum classes (#22228)

Improvements to diagnostics

• Improve diagnostics when attempting to specialize non-generic types (#23516)
• Render subdiagnostics when --output-format=github is specified (#23455)

Performance

• Add a cached method for calculating the intersection of two types (#23547)
• Add a cached method for calculating the union of two types (#23565)
• Reduce the threshold above which Literal types in unions are upcasted to nominal-instance types in situations where the union type is recursively defined (#23521)
• Control flow: isolate the calculation of "loop header reachability" in a dedicated, cached function (#23520)

Contributors

• @​AlexWaygood
• @​silamon
• @​ibraheemdev
• @​Hugo-Polloli
• @​charliermarsh
• @​knutwannheden
• @​oconnor663
• @​carljm
• @​mtshiba

• ae10022 Bump version to 0.0.19 (#2908)
• 6bdb7d7 Update Fathom code for ty (#2890)
• d207424 Update docker/build-push-action action to v6.19.2 (#2880)
• 839cfc3 Update prek dependencies (#2879)
• See full diff in compare view

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