Bump mypy from 1.18.2 to 1.19.0

[dependabot]

Bumps mypy from 1.18.2 to 1.19.0.

Changelog

Sourced from mypy's changelog.

Mypy Release Notes

Next Release

Drop Support for Python 3.9

Mypy no longer supports running with Python 3.9, which has reached end-of-life. When running mypy with Python 3.10+, it is still possible to type check code that needs to support Python 3.9 with the --python-version 3.9 argument. Support for this will be dropped in the first half of 2026!

Contributed by Marc Mueller (PR 20156).

Mypy 1.19

We’ve just uploaded mypy 1.19.0 to the Python Package Index (PyPI). Mypy is a static type checker for Python. This release includes new features, performance improvements and bug fixes. You can install it as follows:

python3 -m pip install -U mypy

You can read the full documentation for this release on Read the Docs.

Python 3.9 Support Ending Soon

This is the last mypy feature release that supports Python 3.9, which reached end of life in October 2025.

Performance Improvements

• Switch to a more dynamic SCC processing logic (Ivan Levkivskyi, PR 20053)
• Speed up type aliases (Ivan Levkivskyi, PR 19810)

Fixed‑Format Cache Improvements

Mypy uses a cache by default to speed up incremental runs by reusing partial results from earlier runs. Mypy 1.18 added a new binary fixed-format cache representation as an experimental feature. The feature is no longer experimental, and we are planning to enable it by default in a future mypy release (possibly 1.20), since it's faster and uses less space than the original, JSON-based cache format. Use --fixed-format-cache to enable the fixed-format cache.

Mypy now has an extra dependency on the librt PyPI package, as it's needed for cache serialization and deserialization.

Mypy ships with a tool to convert fixed-format cache files to the old JSON format. Example of how to use this:

$ python -m mypy.exportjson .mypy_cache/.../my_module.data.ff

... (truncated)

Commits

• 0f068c9 Remove +dev
• 6d5cf52 Various updates to 1.19 changelog (#20304)
• 3c81308 Add draft version of 1.19 release notes (#20296)
• 1999a20 [mypyc] librt base64: use existing SIMD CPU dispatch by customizing build fla...
• 1b94fbb [mypyc] Fix vtable pointer with inherited dunder new (#20302)
• 13369cb [mypyc] Fix crash on super in generator (#20291)
• a087a58 Update import map when new modules added (#20271)
• 35e843c [mypyc] Add efficient librt.base64.b64decode (#20263)
• 094f66d [mypyc] Add repr to AssignmentTarget subclasses (#20258)
• 0738db3 Do not push partial types to the binder (#20202)
• Additional commits viewable in compare view

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Resolves #20304
Resolves #20296
Resolves #20302
Resolves #20291
Resolves #20271
Resolves #20263
Resolves #20258
Resolves #20202

[github-actions]

🤖 Claude Code Review

Code Review Analysis

Overview

This PR updates the mypy dependency from version 1.18.2 to 1.19.0 in the project's linting dependencies.

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Detailed Review

Code Quality

✅ Code follows our style guide

• This is a dependency version update in pyproject.toml - formatting follows TOML standards
• No code style concerns for this change

✅ No commented-out code

• Clean diff with no commented code

✅ Meaningful variable names

• N/A - dependency version update only

✅ DRY principle followed

• N/A - single line change to dependency version

✅ Identify Defects

• No bugs, logic errors, or vulnerabilities introduced
• This is a minor version bump of a development dependency (linting tool)
• mypy 1.19.0 is a legitimate release (released in early 2024)
• Low risk change as it only affects linting, not runtime behavior

✅ Project memory claude configuration

• No .claude/CLAUDE.md file present in the repository to consider

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Testing

⚠️ Unit tests for new functions

• N/A - No new functions added
• However, recommend running full lint suite to ensure mypy 1.19.0 doesn't flag new type issues

⚠️ Integration tests for new endpoints

• N/A - No new endpoints

⚠️ Edge cases covered

• N/A - Dependency update

⚠️ Test coverage > 80%

• Cannot verify from diff alone
• This change should not affect test coverage as it's a linting tool update

Recommendation: Verify that existing type hints pass with mypy 1.19.0 without new errors

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Documentation

✅ Readme updated if needed

• No README update needed for minor linting dependency bump

✅ API docs updated

• N/A - No API changes

✅ Inline comments for complex logic

• N/A - No code logic changes

⚠️ CHANGELOG.md updated

• pyproject.toml:76 - No CHANGELOG.md update visible in diff
• For a minor linting dependency update, this may be acceptable depending on project policy
• Consider adding entry like: "Bumped mypy from 1.18.2 to 1.19.0"

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Security

✅ No hardcoded credentials

• No credentials in diff

✅ Input validation implemented

• N/A - Dependency update only

✅ Proper error handling

• N/A - Dependency update only

✅ No sensitive data in logs

• N/A - Dependency update only

✅ No license files (.lic) or AQAAAD strings

• No license files or suspicious strings in diff

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Summary

Overall Assessment: ✅ APPROVED with minor recommendations

This is a low-risk, straightforward dependency update for a development tool. The change:

• Updates mypy from 1.18.2 to 1.19.0 (minor version bump)
• Only affects linting/type checking, not runtime behavior
• No security concerns
• No functional code changes

Recommendations:

1. ⚠️ Verify linting passes: Run mypy against the codebase to ensure no new type errors are flagged by version 1.19.0
2. ⚠️ Consider CHANGELOG update: Document dependency updates if that's project policy
3. ✅ CI/CD verification: Ensure automated linting checks pass with the new version

Risk Level: LOW

This change only affects the development/linting environment and should not impact production behavior.

Automated code review analyzing defects and coding standards