[ty] Use Top materializations for TypeIs special form by AlexWaygood · Pull Request #20591 · astral-sh/ruff (original) (raw)

added the ty

Multi-file analysis & type inference

label

Sep 26, 2025

AlexWaygood changed the titleUse Top materializations for TypeIs special form [ty] Use Top materializations for TypeIs special form

Sep 26, 2025

dcreager added a commit that referenced this pull request

Sep 30, 2025

• main: (21 commits) [ty] Literal promotion refactor (#20646) [ty] Add tests for nested generic functions (#20631) [cli] Add conflict between --add-noqa and --diff options (#20642) [ty] Ensure first-party search paths always appear in a sensible order (#20629) [ty] Use typing.Self for the first parameter of instance methods (#20517) [ty] Remove unnecessary parsed_module() calls (#20630) Remove TextEmitter (#20595) [ty] Use fully qualified names to distinguish ambiguous protocols in diagnostics (#20627) [ty] Ecosystem analyzer: relax timeout thresholds (#20626) [ty] Apply type mappings to functions eagerly (#20596) [ty] Improve disambiguation of class names in diagnostics (#20603) Add the The Basics title back to CONTRIBUTING.md (#20624) [playground] Fix quick fixes for empty ranges in playground (#20599) Update dependency ruff to v0.13.2 (#20622) [ruff] Fix minor typos in doc comments (#20623) Update dependency PyYAML to v6.0.3 (#20621) Update cargo-bins/cargo-binstall action to v1.15.6 (#20620) Fixed documentation for try_consider_else (#20587) [ty] Use Top materializations for TypeIs special form (#20591) [ty] Simplify Any | (Any & T) to Any (#20593) ...

suleymanozkeskin added a commit to suleymanozkeskin/ruff-ty-typeis-fix that referenced this pull request

Dec 1, 2025

Fixes astral-sh#1703

Fixes incomplete type narrowing when using TypeIs with generic union types like: Result[T, E] = Ok[T] | Err[E].

Previously, type parameter E was materialized to 'object' before specialization could substitute it with concrete types like Exception, causing narrowing to produce Err[Unknown] instead of Err[Exception].

Changes:

• Added is_materialized flag to TypeIsType to defer materialization
• Implemented class-based union element matching for multi-typevar unions in generics.rs
• Modified TypeIs creation to delay materialization until after specialization
• Added test case for generic TypeIs narrowing to type_guards.md
• Removed the comments which had a discussion about: astral-sh#20591

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