Microsoft/TypeScript

Control Flow Analysis Performance Regression

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#62.050 geöffnet am 12. Juli 2025

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Domain: PerformanceHelp WantedPossible Improvement

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Beschreibung

🔎 Search Terms

Control Flow

🕗 Version & Regression Information

⏯ Playground Link

No response

💻 Code

🙁 Actual behavior

I encountered a severe performance regression when type-checking a very large JavaScript file (~360,000 lines).

v4.9.5: Type-checking takes ~16,476ms.

v5.5.4: Type-checking time increases to ~64,196ms (4x slower).

Steps to Reproduce:

  1. Clone the attached project and run:
npm install
node checker.js
  1. Switch TypeScript versions (e.g., between v4.9.5 and v5.5.4) and re-test.

After testing, I believe this regression was introduced by PR #58013. When I revert this commit, the performance returns to v4.9.5 levels.

testLargeFile.zip

🙂 Expected behavior

The performance is the same as v4.9.5

Additional information about the issue

No response

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