[Repo Assist] Monthly Activity 2026-04

🤖 *Repo Assist here — I'm an automated AI assistant for this repository.*

## Activity for April 2026

## Suggested Actions for Maintainer

**Comprehensive list** of all pending actions requiring maintainer attention (excludes items already actioned and checked off).

* [ ] **Review PR** [#19472](https://github.com/dotnet/fsharp/pull/19472): fix for [#12796](https://github.com/dotnet/fsharp/issues/12796) — empty array support in custom attributes — has merge conflicts — [Review](https://github.com/dotnet/fsharp/pull/19472)
* [ ] **Close issue** [#5418](https://github.com/dotnet/fsharp/issues/5418): confirmed fixed (PR #19504 merged 2026-04-11), existing test coverage in WarnExpressionTests.fs — [View comment](https://github.com/dotnet/fsharp/issues/5418#issuecomment-4252432195)
* [ ] **Close issue** [#13512](https://github.com/dotnet/fsharp/issues/13512): confirmed fixed (PR #19506 merged 2026-04-11), comprehensive test coverage in CompletionTests.fs — [View comment](https://github.com/dotnet/fsharp/issues/13512#issuecomment-4252432482)
* [ ] **Check comment** on [#13099](https://github.com/dotnet/fsharp/issues/13099): Task CE optimizer correctness bug — `(someFunctionWithReturnType()).End` silently optimized away in Release mode — [View](https://github.com/dotnet/fsharp/issues/13099#issuecomment-aw_K82zWkQU)
* [ ] **Check comment** on [#16982](https://github.com/dotnet/fsharp/issues/16982): delegate keyword breaks semantic highlighting — reproduced via FCS, AI-thinks-windows-only removed — [View](https://github.com/dotnet/fsharp/issues/16982#issuecomment-4170012826)
* [ ] **Check comment** on [#18841](https://github.com/dotnet/fsharp/issues/18841): `let _ = &s` still raises FS0421 — AI-thinks-issue-fixed was incorrectly applied then removed — [View](https://github.com/dotnet/fsharp/issues/18841#issuecomment-4162657922)
* [ ] **Check comments** on [#16034](https://github.com/dotnet/fsharp/issues/16034), [#16464](https://github.com/dotnet/fsharp/issues/16464): confirmed still present, Repo Assist provided repro details

## Additional observations for maintainer's attention

* Issue [#13099](https://github.com/dotnet/fsharp/issues/13099): **High-impact optimizer correctness bug** — `(someFunctionWithReturnType()).End` where `.End` is a unit property causes the function call to be optimized away in Release mode, silently swallowing the side effect (including `failwith`). Confirmed with F# 11.0 on .NET 10.
* Issue [#15627](https://github.com/dotnet/fsharp/issues/15627): `async { } |> Async.RunSynchronously` at module level before `[]` still deadlocks. Confirmed on F# 11.0 / .NET 10.
* Issue [#12303](https://github.com/dotnet/fsharp/issues/12303): `AddBackticksToIdentifierIfNeeded "not"` still returns ``` ``not`` ``` (incorrect — `not` is a stdlib function, not a keyword). Also, `params` and `parallel` are NOT getting backticks when they should.
* Issue [#12379](https://github.com/dotnet/fsharp/issues/12379): Recursive type with `Zero` constraint still fails to compile. dsyme confirmed this is a phasing bug in the type checker.
* Issue [#16292](https://github.com/dotnet/fsharp/issues/16292): **Debug-only codegen bug** — SRTP with mutable struct enumerator causes infinite loop in Debug builds. Release works correctly. Verified: Debug build hangs (timeout after 5s), Release prints expected output. The struct enumerator's `MoveNext()` mutation is lost due to defensive copying.

## Future Work for Repo Assist

* Task 1: Cursor at 0 (full scan complete) — monitoring for new activity on pre-2024 bugs
* Task 3: woc=18119 — all windows-only issues reassessed; monitoring for newly labeled issues
* Task 2: rtc=14566 — monitoring for newly labeled AI-thinks-issue-fixed issues

## Run History

### 2026-04-29 01:16 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/25086023839)
- 🔍 Scanned for pre-2024 bugs with activity since 2026-04-28: none found
- 🔍 Checked AI-thinks-windows-only issues: none above cursor (woc=18119)
- 🔍 Checked AI-thinks-issue-fixed issues: #5418 and #13512 already verified with test coverage in prior runs (rtc=14566)
- 📊 No new actions — all pending items unchanged since last run

### 2026-04-28 01:15 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/25028408548)
- 🔍 Scanned for pre-2024 bugs with activity since 2026-04-27: none found
- 🔍 Checked AI-thinks-windows-only issues: none above cursor (woc=18119)
- 🔍 Checked AI-thinks-issue-fixed issues: #5418 and #13512 already verified with test coverage in prior runs (rtc=14566)
- 📊 No new actions — all pending items unchanged since last run

### 2026-04-27 01:12 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24971896927)
- 🔍 Scanned for pre-2024 bugs with activity since 2026-04-26: none found
- 🔍 Checked AI-thinks-windows-only issues: none above cursor (woc=18119)
- 🔍 Checked AI-thinks-issue-fixed issues: #5418 and #13512 already verified with test coverage in prior runs (rtc=14566)
- 📊 No new actions — all pending items unchanged since last run

### 2026-04-26 01:12 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24944942518)
- 🔍 Scanned for pre-2024 bugs with activity since 2026-04-25: none found
- 🔍 Checked AI-thinks-windows-only issues: none above cursor (woc=18119)
- 🔍 Checked AI-thinks-issue-fixed issues: #5418 and #13512 already verified with test coverage in prior runs (rtc=14566)
- 📊 No new actions — all pending items unchanged since last run

### 2026-04-24 01:10 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24866975706)
- 🔍 Scanned for pre-2024 bugs with activity since 2026-04-23: none found
- 🔍 Checked AI-thinks-windows-only issues: none above cursor (woc=18119)
- 🔍 Checked AI-thinks-issue-fixed issues: #5418 and #13512 already verified with test coverage in prior runs
- 📊 No new actions — all pending items unchanged since last run

### 2026-04-21 12:52 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24723313687)
- 🔍 Scanned 31 pre-2024 bugs (#16083–#16464): all confirmed still present on F# 11.0 (FSI 15.2.101.0, commit `92fd65a`)
- 🔍 Verified #16292 (Debug codegen infinite loop), #16254 (unit literal FS0768), #16344 (typeof in attribute), #16432 (3x duplicate FS0039), #16454/#16455 (FS3559 false positives), #16189 (TryFinally exception loss)
- 📊 Cursor completed full pre-2024 range → reset to 0; PR #19613 merged, #3783 closed

### 2026-04-21 01:08 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24698630806)
- 🔍 Scanned ~40 pre-2024 bugs (#12281–#15940): all confirmed still present
- 💬 Commented on [#13099](https://github.com/dotnet/fsharp/issues/13099): Verified optimizer correctness bug — `(someFunctionWithReturnType()).End` silently optimized away in Release mode, Debug works correctly
- 📊 Updated cursor from 11770 → 15940

### 2026-04-20 12:54 UTC — [Run](https://github.com/dotnet/fsharp/actions/runs/24667580200)
- 🔍 Scanned ~20 pre-2024 bugs (#9994–#11770): all confirmed still present
- 💬 Commented on [#11626](https://github.com/dotnet/fsharp/issues/11626): verified still present via FCS UnusedOpens API
- 📊 Updated cursor from 9838 → 11770

### Earlier runs (2026-04-01 through 2026-04-20)
- Investigated pre-2024 bugs, reassessed windows-only issues, created regression tests
- PRs merged: #19476, #19530, #19471, #19468, #19579, #19580, #19581, #19613

> Generated by 🌈 Repo Assist, see [workflow run](https://github.com/dotnet/fsharp/actions/runs/25086023839). [Learn more](https://github.com/githubnext/agentics/blob/main/docs/repo-assist.md).
>
> To install this [agentic workflow](https://github.com/githubnext/agentics/blob/7c7feb61a52b662eb2089aa2945588b7a200d404/workflows/repo-assist.md), run
> ```
> gh aw add githubnext/agentics/workflows/repo-assist.md@7c7feb61a52b662eb2089aa2945588b7a200d404
> ```