[ty] Add unbound type variable detection in annotations by AlexWaygood · Pull Request #23641 · astral-sh/ruff (original) (raw)

added the ty

Multi-file analysis & type inference

label

Mar 1, 2026

… their bound scope

This adds validation for three missing checks around correct use of type variables:

1. Reject unbound type variables in module-scope annotations (e.g., x: T)
2. Reject unbound type variables in function/class bodies where they aren't part of the enclosing generic context (e.g., S inside def f(x: T))
3. Reject type variables from outer class scopes used in inner class bodies (e.g., class C[T]: class Bad: x: T)

The implementation:

• Adds a new UNBOUND_TYPE_VARIABLE lint rule in diagnostic.rs
• Modifies bind_typevar in generics.rs to track class scope boundaries, preventing inner classes from accessing outer class type parameters
• Adds check_for_unbound_type_variable method in type_expression.rs that detects when a TypeVar remains unbound after in_type_expression processing
• Uses a check_unbound_typevars flag on the builder, enabled only during annotation expression processing, to avoid false positives in TypeVar defaults, explicit class specialization, and other internal contexts
• Updates existing TODO test comments in scoping.md to proper error assertions

https://claude.ai/code/session_01FUqdwkfw72xwPnuhqqpvp6

Co-authored-by: Douglas Creager dcreager@dcreager.net

carljm removed their request for review

March 2, 2026 15:55

AlexWaygood deleted the claude/add-type-variable-validation-pw9Ns branch

March 2, 2026 16:01

carljm added a commit that referenced this pull request

Mar 2, 2026

• main: (30 commits) [ty] Introduce types::bool, types::context_manager and types::iteration (#23681) [ty] Move KnownInstanceType, and related types, to a new known_instance.rs submodule (#23680) [ty] Add invalid-enum-member-annotation lint rule (#23648) [ruff] Fix false positive for re.split with empty string pattern (RUF055) (#23634) [ty] Move UnionType and IntersectionType to a new types::set_theoretic submodule (#23678) [ty] Add unbound type variable detection in annotations (#23641) [ty] Remove specialize_constrained from constraint set module (#23677) [ty] Add partial support and validation for Unpack when used with tuple types (#23651) Update prek dependencies (#23661) [ty] make StaticClassLiteral::explicit_bases converge better in cycles (#23601) Improvements to CLAUDE.md (#23633) [ty] Move subscript logic out of builder.rs (#23653) Update Artifact GitHub Actions dependencies (#23676) Update actions/attest-build-provenance to 4.1.0 (#23654) Update Rust crate clearscreen to v4.0.5 (#23664) fix renovate actions/*-artifact updates (#23675) Update Rust crate clap to v4.5.60 (#23663) Update Rust crate unicode-ident to v1.0.24 (#23668) Update Rust crate anyhow to v1.0.102 (#23662) Update Rust crate pyproject-toml to v0.13.7 (#23666) ...

This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.Learn more about bidirectional Unicode characters

[ Show hidden characters]({{ revealButtonHref }})