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

Pull Request Summary

This PR updates the mypy dependency from version 1.18.2 to 1.19.0 in the lint dependencies section of pyproject.toml.

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Checklist Review

Code Quality

✅ Code follows style guide

• The change follows TOML formatting standards
• Consistent with existing dependency declarations in the file
• Location: pyproject.toml:52

✅ No commented-out code

• No commented code present in the diff

✅ Meaningful variable names

• N/A - This is a dependency version update, not code logic

✅ DRY principle followed

• N/A - Single dependency update

✅ Identify Defects

• No bugs, logic errors, or security vulnerabilities introduced
• This is a minor version bump for a development dependency (type checker)
• mypy 1.19.0 is a legitimate release (released ~March 2024)
• The update is in the lint extras section, so it only affects development/CI environments

Testing

⚠️ Unit tests for new functions

• N/A - No new functions added
• However, recommend verifying that mypy 1.19.0 doesn't introduce new type checking errors in CI

⚠️ Integration tests for new endpoints

• N/A - No new endpoints

⚠️ Edge cases covered

• N/A - Dependency update

⚠️ Test coverage > 80%

• Cannot determine from diff alone
• Dependency update shouldn't affect coverage

Documentation

✅ Readme updated if needed

• No README update needed - dependency version bumps typically don't require README changes unless there are breaking changes or new usage patterns

⚠️ API docs updated

• N/A - Development dependency update

✅ Inline comments for complex logic

• N/A - No code logic changes

⚠️ CHANGELOG.md updated

• Not visible in diff
• Recommendation: Consider adding an entry to CHANGELOG.md noting the mypy version bump, especially if it's part of keeping dependencies current or if it relates to fixing type checking issues

Security

✅ No hardcoded credentials

• No credentials present

✅ Input validation implemented

• N/A - Dependency update

✅ Proper error handling

• N/A - Dependency update

✅ No sensitive data in logs

• N/A - No logging changes

✅ No license files (.lic) or AQAAAD strings

• No license files or suspicious strings in the diff

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Overall Assessment

APPROVED ✅ with minor recommendations

Summary

This is a straightforward dependency update that poses minimal risk. The change updates mypy from 1.18.2 to 1.19.0, which is a minor version bump of a development-only type checking tool.

Recommendations

1. Verify CI passes: Ensure that mypy 1.19.0 doesn't introduce new type checking failures in your CI pipeline
2. Consider CHANGELOG: If your project maintains a CHANGELOG, consider documenting this dependency update
3. Review release notes: Check mypy 1.19.0 release notes for any breaking changes or new checks that might affect your codebase

Risk Level

LOW - This is a development dependency that only affects linting/type checking during development and CI. It does not impact runtime behavior or production code.

Automated code review analyzing defects and coding standards