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Brief: #999, a grammar rule whose result is a tuple mixing String with another type refuses the views its action builds (NK1104)

Score: S=3 (a wrong refusal, blocks the yaml lane’s flow mappings, #928), O=1 M (the yaml lane waits or writes a struct around it), C=5 M (b-tuple tiers of 2f73c24, #929), area bugs. First of this batch: a defect another lane is blocked on.

Issue #999 (copied; re-probed by the architect at c30b7bc0)

grammar G {
    rule WS = "" -> { }
    rule Pair -> (String, i64) = k:until(":") ":" n:dec[i64] -> { (k, n) }
    entry rule doc -> (String, i64) = p:Pair eof -> { p }
}

fn main() throws {
    let (k, n) = G::doc("ab:12")
    println(f"{k} {n}")
}

Today: error[NK1104]: This action builds (ref String, i64), but its rule returns (String, i64). at the p of doc (line 4). Expected ab 12. Also refused the same way (architect, c30b7bc0): rule Pair -> (String, Value) = k:until(":") ":" n:dec[i64] -> { (k, Value::Num(n)) } with enum Value { Str(String), Num(i64) }. An all-String tuple takes the views (2f73c24, #929, test grammar_a_tuple_result_takes_the_views_its_action_builds), and so does a struct { key: String, value: Value }.

A function with a mixed tuple result already works: fn pair(s: String) -> (String, i64) { return (s.trim(), 1) } called with a named argument prints ab1 1. So the gap is in the grammar pass of the tier walk (the error names the rule doc, which hands on p:Pair). Not this brief: the same function called with a temporary argument (pair(f" ab{1} ")) fails in rustc; that is #1036, leave it.

Locations

To build

  1. A tuple result of a grammar rule whose parts mix String (or an enum/struct holding views) with other types takes the views its action builds, no ref written (ADR-282 D1, D2), as an all-String tuple does, also when another rule hands it on through a label (p:Pair -> { p }).
  2. Test tests/compiler/tests/grammar_a_mixed_tuple_result_takes_views.nika with its .stdout: the probe above (ab 12) and the (String, Value) rule beside it, its Value::Num matched and printed. Run it against the unfixed compiler first (it must fail with NK1104), then fixed; run the existing grammar_a_tuple_result_* and grammar_*tuple* tests.

Only text_tiers.nika, check_grammar.nika, check_function.nika, their lowered files (and lowered.rs) and the new test are yours. Another file needed: stop, report partial with what and why. Stop about 15 turns before max_turns: commit what is finished and report partial.

The commit that finishes it says Fixes #999.

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/bugs/b1-999-mixed-tuple-views.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 a lowering other than the brief’s where rustc cannot take the brief’s, b1029 2026-10-31: say why 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:, nor an existing test’s expected .stdout/.stderr updated because your change rightly changes the message it prints, b1012b 2026-10-31: name the test 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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