ty 0.0.19

on Python PyPI

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

Install ty 0.0.19

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.19/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.19/ty-installer.ps1 | iex"

Download ty 0.0.19