astral-sh/ty 0.0.20

on GitHub

Release Notes

Released on 2026-03-02.

Bug fixes

• Disallow negative narrowing for isinstance() or issubclass() checks involving type[] types (#23598)
• Fix binary operations between an instance of a NewType of float and an instance of Any/Unknown (#23620)
• Fix bug where ty would think that a Callable with a variadic positional parameter could be a subtype of a Callable with a positional-or-keyword parameter (#23610)
• Fix inference of t.__mro__ if t is an instance of type[Any] (#23632)
• Fix overloaded callable assignability for unary Callable targets (#23277)
• Limit recursion depth when displaying self-referential function types (#23647)
• Ensure that python -m ty works even when ty was installed into an ephemeral virtual environment (#2852)

LSP server

• Add support for the LSP protocol's "type hierarchy" feature (#23566)

Type checking

• Add more ParamSpec validation for P.args and P.kwargs (#23640)
• Ban nested Required/NotRequired, and ban them both outside of TypedDict fields (#23627)
• Detect inconsistent generic base class specializations that appear in the same MRO (#23615)
• Detect invalid uses of @final on non-methods (#23604)
• Add partial support and validation for Unpack when used with tuple types (#23651)
• Recurse into tuples and nested tuples when applying special-cased validation of arguments passed to isinstance() and issubclass() (#23607)
• Reject ellipsis literals in odd places in type/annotation expressions (#23611)
• Reject functions with PEP-695 type parameters that shadow type parameters from enclosing scopes (#23619)
• Reject generic metaclasses parameterized by type variables (#23628)
• Treat dataclass_transform dataclasses as neither frozen nor non-frozen (#23366)
• Validate that type variable defaults don't reference later type parameters or type parameters out of scope (#23623)

Typeshed

• Sync vendored typeshed stubs (#23642). Typeshed diff

Contributors

• @Hugo-Polloli
• @zanieb
• @sharkdp
• @mtshiba
• @carljm
• @charliermarsh
• @sinon
• @BurntSushi
• @oconnor663
• @AlexWaygood
• @zsol

Install ty 0.0.20

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/ty/releases/download/0.0.20/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://github.com/astral-sh/ty/releases/download/0.0.20/ty-installer.ps1 | iex"

Download ty 0.0.20