ty 0.0.22

on Python PyPI

Release Notes

Released on 2026-03-12.

Bug fixes

• Fix issue where variables could be inferred as Divergent if they were assigned using tuple unpacking in loops (#23812)
• Allow error = "all" in a root pyproject.toml file to be overridden using tool.ty.overrides in a subdirectory's pyproject.toml file (#23712)
• Only unsoundly upcast type[] types to their constructor Callable type during assignability checks, not during redundancy/subtyping checks (#23834, #23901)
• Fix stack overflow that could occur with certain recursive protocols (#23870)

LSP server

• Improve syntax highlighting by fixing semantic token classification for generic class members in annotations (#23811)

CLI

• Add ty explain <RULE> CLI command (#23766)

Core type checking

• Add validation for type parameters with defaults after TypeVarTuple parameters (#23807)
• Allow subtypes of LiteralString to be narrowed using equality checks (#23794)
• Detect invalid partially stringified PEP-604 unions (#23285)
• Disambiguate duplicate-looking overloaded callables in union display (#23907)
• Don't promote module-literal types to types.ModuleType (#23786)
• Improve type context support for __setitem__ dunder calls (#23800)
• Infer t | {"foo": int} as TD if t is an instance of a TypedDict td with a foo: int key (#23806)
• Narrow T to T & str rather than str if T is a constrained TypeVar with str as one of its constraints (#23850)
• Promote None to None | Unknown in invariant contexts (#23790)
• Reject type[Callable] in type annotations (#23753)
• Support enum member access through enum instances and members (#23772)
• Eagerly narrow the type associated with keys of heterogeneous dict literals even when a dict literal appears as a subexpression inside a list or tuple literals (#23569)
• Ensure that T & ~S is always inferred as a subtype of U during generic inference if T is understood as a subtype of U (#23728)
• Optimize and improve cycle recovery by preventing "tainted" unions in cycle normalization (#23563)

Installer

• Prefer downloading releases from Astral's mirror over GitHub (#2980)

Contributors

• @charliermarsh
• @MichaReiser
• @mtshiba
• @AlexWaygood
• @ibraheemdev
• @ntBre
• @oconnor663
• @zsol

Install ty 0.0.22

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://releases.astral.sh/github/ty/releases/download/0.0.22/ty-installer.sh | sh

Install prebuilt binaries via powershell script

powershell -ExecutionPolicy Bypass -c "irm https://releases.astral.sh/github/ty/releases/download/0.0.22/ty-installer.ps1 | iex"

Download ty 0.0.22