agent: builder model: opus max_turns: 80 budget_usd: 15 —
let f = fs[0] of a kept fn value moves out of the Vec (rustc)Score: compiler bug (false acceptance: the checker passes, rustc refuses), bugs-first default of docs/priorities.md.
fn main() {
let mut fs: Vec[fn(i64) -> i64] = []
fs.push(fn(x) { x + 1 })
let f = fs[0]
println(f(2))
let g = fs[0]
println(g(2))
println(g(2))
}Today: rustc Cannot move out of a shared reference at let f = fs[0]. Expected 3, 3, 3. Part I (10-nikaia-light.md about line 2234): a function value in any of them is kept: … a copy of the value shares the one closure. So an index read of a fn-typed element is a copy: lowered as a clone of the nikaia_std::func::Kept handle (an Arc, ADR-277 D11), cheap.
Not in this brief: the issue’s row fs[0](2) does not parse (Expected ')'; calling an index result is no form of Part I), and fs[0].clone() is NK1245; leave both.
emit_core_index_expr in crates/nikaia-std/src/tools/emit_host.nika:158, and emit_core_reads.nika about line 466-510.a_copy_by_value in crates/nikaia-std/src/tools/check_types.nika:89 (and value_of_a_copy, line 73). Find how a String element read by index is cloned or refused today and follow the path that decides it (checker fact or emitter test); a fn type joins the cloned case. If the decision is a checker fact, name it in the commit (check_facts.nika, keyed by node_key); the checker files are allowed.emit_core_types.nika about line 185-219 (nikaia_std::func::Kept<dyn Fn..>).fn-typed element bound by let (or handed to a kept position) lowers to a clone of the handle. Test tests/compiler/tests/a_kept_fn_read_by_index.nika + .stdout: the probe above (3, 3, 3). Commit emit: a kept fn read by index shares the closure (#1018), Fixes #1018.The test passes through nikaia test; lower-std fixpoint clean; cargo build --profile fast -p nikaia; the guard set of .claude/agents/builder.md green; pushed. Changelog: one line (a function value read from a list by index shares the closure, Part I).
An edit is needed outside crates/nikaia-std/src/tools/emit_*.nika, check_*.nika, check_types.nika, their lowered files and the new test; an error in another agent’s file.
Not yours, never stage: every file git status shows modified or untracked at your start, and every docs/briefs/* file except your report.
docs/builder-facts.md first. develop in the main checkout; git status at start: other agents’ uncommitted files are not yours, never touch or stage them.git add <files> only; commit after each step; git push origin develop fast-forward, no rebase (rejected: report Pushed: rejected, go on committing).cargo fmt, cargo clippy --all-targets -- -D warnings, scripts/pre-push-check.sh, and the gate of .claude/agents/builder.md (#852).CHANGELOG.md, badges; no new NK code. New tests in Nikaia only; never the full suite. No foreground sleep, no polling; scripts in files.std or the toolchain lacks stops the work: no code around it unless an ADR or Part I-III refuses it (name it). Else Result: blocked, Found: gap + probe, Needs: owner decision (CLAUDE.md, A missing form stops the work).NIKAIA_CACHE_LIMIT=2G; at most two clones with target/ in the machine; delete your own clone’s target/ and target/release/nikaia-scratch at the end; report GB freed.Pushed: line names the pushed sha. A report without a Pushed: line, or with a placeholder left in (TC, DISK), is not done and cuts the batch (k3a1 2026-10-29: Result: done, nothing committed)./home/user/Nikaia/docs/briefs/b1018-kept-fn-index-read.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:, 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