Write Comments That Explain Why
Added 2026-10-31
Turn what-comments into why-comments so future readers can judge whether it is safe to change.
Below is code with existing comments. Do: 1) find comments that merely restate what the code does; 2) rewrite the ones worth keeping as a why (constraints, trade-offs, past incidents); 3) keep each to two lines; 4) flag the spot a future reader is most likely to break and add one warning line. Do not change the logic.
Site original
Chinese original
How to use
好注释解释取舍，不解释语法。
Try tweaking it
- Have it restate requirements and constraints before writing code.
- Ask for the smallest change plus a rollback path, not a full-file rewrite.
What you should get
- A minimal, runnable change with copy-ready code
- Impact list: which files and call sites must follow
Common mistakes
- Asking it to touch ten files at once, then losing track of what broke what.
- Pasting only the error, with no code or version, and getting an unfixable answer.
How to check the output
- The change runs, can be rolled back, and touches nothing unrelated.
- Edge cases (empty, oversized, concurrent) are covered or explained.
Where it works
- Good for: having it restate requirements and constraints, then propose the smallest runnable change.
- Watch out: include versions and a minimal reproduction with the error, or the fix may look plausible but not fit.