Fix a 3.9 issue. add _typing.py to dist check

[oraluben]

Summary by CodeRabbit

Release Notes

Chores

• Updated continuous integration workflows to prioritize Python 3.9 as the minimum supported version
• Extended distribution check triggers to cover additional project modules
• Improved type annotation compatibility with Python 3.9 standards

[github-actions]

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[coderabbitai]

📝 Walkthrough

Walkthrough

CI/CD workflows updated to drop Python 3.8 support, maintain 3.9 with renamed step identifiers, and extend distribution checks. Type annotation syntax in tilelang/_typing.py changed from Python 3.10+ union syntax to explicit typing.Union for Python 3.9 compatibility.

Changes

Cohort / File(s)	Summary
CI/CD Workflows .github/workflows/ci.yml, .github/workflows/dist.yml	Removed Python 3.8 setup step; renamed Python 3.9 setup step to setup-pylowest and added corresponding AST check. Extended dist workflow trigger to include tilelang/_typing.py in PR/dist path.
Type Annotations tilelang/_typing.py	Changed PyPrimExpr TypeAlias from Python 3.10+ union syntax (tir.PrimExpr | int | float | bool) to explicit Union[tir.PrimExpr, int, float, bool] for Python 3.9 compatibility. Updated associated documentation note.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested reviewers

• LeiWang1999

Poem

🐰 Hoppy hops through Python's lanes,
From 3.8 we break the chains,
Union types in dapper dress,
Compatibility, nothing less! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the two main changes: fixing a Python 3.9 compatibility issue and adding _typing.py to the dist check workflow.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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