[repo-assist] Improve: replace ref cell with mutable in mergeAll - #350
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AsyncSeq.mergeAll used a ref<int> for its internal live-task counter, which allocates a Ref wrapper object on the heap per call. This was the last remaining ref cell of this kind in the codebase after prior modernization passes (ofSeq, tryWith, tryFinally, pairwise, distinctUntilChangedWithAsync). Replaced with a direct mutable local for consistency and to avoid the allocation. No behavioral change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
AsyncSeq.mergeAllusedlet fin = ref nto track the number of live source sequences, withfin.Valuemutated on every completion. This was the last remainingrefcell of this kind in the codebase — earlier releases (4.16.0, and the perf work onpairwise/distinctUntilChangedWithAsync) already replaced equivalentrefusages with directmutablelocals to avoid the per-call heap allocation of theRef<'T>wrapper object.This PR applies the same modernisation to
mergeAllfor consistency and to eliminate that allocation.Changes
src/FSharp.Control.AsyncSeq/AsyncSeq.fs:mergeAll—let fin = ref n→let mutable fin = n;fin.Valuereads/writes → directfinreads/writes.RELEASE_NOTES.md: added an entry under Unreleased.No public API or behavioral changes.
Test Status
dotnet build FSharp.Control.AsyncSeq.sln -c Release— succeeded, 0 errors.dotnet test tests/FSharp.Control.AsyncSeq.Tests -c Release— 497/497 tests passed, including the existingmergeAlltests (should work,should perform well,should be fair,should fail with AggregateException if a task fails).🤖 This PR was created by Repo Assist, an automated AI assistant, as part of scheduled coding-improvement maintenance (Task 5). A human maintainer should review before merging.
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