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agent: builder model: opus max_turns: 100 budget_usd: 20 —

Brief #934: NK2605 although the value is closed by hand (f.close() catch { ... })

Score: bugs before moving (CLAUDE.md, docs/priorities.md); a wrong refusal whose own help text recommends the refused form, and it blocks the move of project.rs’ trace (plan row P5a). Checker lane only (check_crossings.nika, check_compare.nika); the first brief of this batch is in the lowering (views.nika / text_tiers.nika).

Issue text (#934, copied; builders have no GitHub)

Found by P5a (2e13458). A value with a Cleanup whose cleanup can fail, closed explicitly with close() and a statement catch, is still refused with NK2605. Probe (re-run on 6ccf6c8: NK2605 at the let, line 24; expected output close: closed would not flush then after close):

enum FlushError {
    Refused(String),
}

impl Error for FlushError {
    fn message(ref self) -> String {
        match self {
            FlushError::Refused(name) => f"{name} would not flush"
        }
    }
}

struct Flaky {
    name: String,
}

impl Cleanup for Flaky {
    fn cleanup(ref mut self) throws {
        throw FlushError::Refused(f"{self.name}")
    }
}

fn closing() {
    let f = Flaky { name: f"closed" }
    f.close() catch { println(f"close: {error}") }
    println("after close")
}

fn main() {
    closing()
}

The it test cleanup_points (FLAKY, crates/nikaia/tests/it/cleanup_points.rs:142) holds this very closing(), but it lowers without the checker, so it never saw NK2605. The refusal’s help even says close it yourself where you want to handle the failure: f.close() catch { … }.

Locations (resolved 2026-10-29)

To build

  1. Tests in tests/compiler/tests/: a_failing_cleanup_closed_by_hand_is_handled.nika (the probe, .stdout close: closed would not flush\nafter close\n), and a_failing_cleanup_left_to_the_block_end_is_nk2605.nika (the same without the close() line, .stderr with NK2605, the shape of the other .stderr tests there). Run the first on the unfixed compiler and see NK2605.
  2. Fix in the checker: NK2605 for a failing cleanup asks only of a value whose cleanup is implicit, i.e. still held where its block ends; a value closed with close() (its failure handled by the catch, or passed on in a throws function) on every path is not refused. One way: keep the finding pending at the let and drop it when the value is closed; you choose, and say which in Body:. A value closed on one branch only stays refused. lower-std twice (fixpoint). Commit Fixes #934.

Done when

Both new tests pass run through target/fast/nikaia test --project tests/compiler filtered to their names (the .stdout is compared byte for byte), cargo test -p nikaia --test it -- cleanup errors_lowering file_paths, the gate of .claude/agents/builder.md (a change to tools/check_*.nika runs nikaia test --both-settings --project tests/compiler), clippy, cargo fmt, scripts/pre-push-check.sh. Changelog: one sentence.

Stop and report if

The rule needs a choice Part I or ADR-297 leaves open (a close on one branch, a close inside a loop): name it under Owner:; or the fix needs a file another agent has uncommitted (git status first; crates/rs2nika/convert/nikaia.* were another session’s).

Rules (CLAUDE.md; this block is pasted into every brief, also a fix-forward)

Report (at most 15 lines, to exactly /home/user/Nikaia/docs/briefs/b934-closed-by-hand.md.report.md)

Fields of docs/architect.md, Briefs and reports: Result: done|noop|partial|blocked (the bare word alone on that line: Result: done, never a summary after it, which cuts the batch, b869a 2026-10-27; Owner: is a question for the owner or none, never a role), Files, Commit, Body (optional, one paragraph for the commit message), Fixes, Pushed, Tests, Gate (green|red), Deviation, Found, Needs, Changelog, Owner, Disk freed, and for a move Rs2nika: (the kept N of M lines of rs2nika --score, then the three costliest hand edits; none for a task that moves no Rust, none (redesign) for a brief with Shape: redesign and no Convert: line). none where nothing, and then the bare word: Deviation: none (a note) cuts the batch (batch.nika compares exactly); a note goes into the commit message. Found: is only for a defect outside your change (it cuts the batch); a process event such as another session resetting or rewriting your files is no Found:, it goes under Needs: (m3a 2026-10-28); a converter draft that came out wrong is no Found:, it is one of the costliest edits under Rs2nika:, which the converter lane reads (e12-4b 2026-10-27); how you solved your own step goes into the commit message. Deviation: is only a step of the brief built otherwise than written or not built (a choice the brief left to you, such as keep what X needs and say so, is no deviation: it goes into the commit message; nor is building two steps in one commit when every step is built, e12-3a 2026-10-27, nor a step another commit on develop already built, shown by your test failing with that commit’s change reverted, b889 2026-10-27: name the commit in Body:, nor re-keying an allow-list entry (KNOWN) whose hash changed for the same program and the same reason, b-fixforward-sweep2 2026-10-28: say so in Body:); how you verified (e.g. a test not run against the unfixed compiler) goes under Tests:. A noop says why under Tests: (what was probed), not under Deviation:. Final answer, one line: done <sha>, report <path> (or BLOCKED: ... / PUSH REJECTED ...).

Attribution: Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com Claude-Session: https://claude.ai/code/session_01GFeMqxRbtUMiGVyDMxsvEq

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