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Brief: #994, the NK2104 note for stdout against stderr still recommends seq, which ADR-292 D7 removed

Score: bug lane, a wrong message (S=1, cheap): a refusal that names a form the language does not have sends the reader to a dead end. Builders have no GitHub: the issue text is copied below.

Problem (issue #994, probed by the architect on 9ffc1ec2)

Two overlap branches where one writes stdout and the other stderr are refused with NK2104, correctly (the two count as one destination). The note says Use seq to run them in order., but seq { … } does not exist: ADR-292 D7 removed it, and seq is not a reserved word.

fn a() -> i64 { println("a"); 1 }
fn b() -> i64 { eprintln("b"); 2 }
fn main() {
    let (x, y) = overlap {
        a()
        b()
    }
    println(f"{x} {y}")
}

nikaia check today:

error[NK2104]: These two branches can't run at the same time.
  --> p994.nika:6:9
   ...
   = note: One touches stdout and the other stderr, which might be the same place. Use `seq` to run them in order.
   = note: `overlap` runs its branches at once, so they can't depend on each other.
   = help: If they should run in order, write them as ordinary statements.
1 branch that cannot run beside the others

Locations

To build

  1. In order.nika, drop the seq sentence: the note ends after “which might be the same place” (the help already gives the way out). Re-lower as docs/builder-facts.md says.
  2. Correct the comment in touch.nika (family): the escape is ordinary statements (ADR-292 D1), not seq.
  3. Test tests/compiler/tests/overlap_stdout_stderr_note_names_no_seq.nika with the program above and its .stderr taken from what the compiler prints (run it through nikaia test). If an existing .stderr holds the old sentence (grep -rl 'Use seq' tests/ crates/nikaia/tests), update it.
  4. Commit line: order: the NK2104 note for stdout and stderr no longer names seq (#994), Fixes #994.

Tests

Files

May change: order.nika, touch.nika, their lowered .rs, new files in tests/compiler/tests/, an existing .stderr holding the old sentence. Not yours: crates/rs2nika/convert/nikaia.*, docs/selfhosting-plan.md, any other uncommitted file in the checkout.

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/b994-overlap-note-seq.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 a test’s expected .stdout/.stderr taken from what the program really prints where the brief’s sketch of it was short or wrong, b934 2026-10-29: say so in Body:, nor a lowering that follows the ADR governing it where the brief’s expected lowering contradicts that ADR, b933 2026-10-29: name the ADR 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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