Partial `match` takes a long time to fail
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bug
P-medium
- Dominant language
- Lean
- Stars
- 9.2k
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- 990
- Avg merge
- 1d 17h
- Merged PRs (30d)
- 175
Description
import Lean
def mainLoop (ev : Lean.Server.Watchdog.ServerEvent) : Unit :=
match ev with
| .clientMsg msg => _
takes 7s on a fast machine to fail with maximum heartbeats at whnf. Found when doing an edit in server code that invalidated the other branches.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the mainLoop example with Lean.Server.Watchdog.ServerEvent and observe the delay while whnf processes the partial match. Trace the failure path and heartbeat usage; done means this invalid match fails promptly without exhausting the maximum heartbeat budget.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100