agent: builder model: sonnet max_turns: 100 budget_usd: 20 —
let over a place handed back (let k = p.items; return k fails in rustc)Score: S=3 (a program the checker accepts fails in rustc), O=0.3 M, C=5 M (#848/#864-#866 fixes), bugs lane 1 (docs/priorities.md).
The #453 step 3 builder hit this. Probe (reproduces at f691147, target/fast/nikaia run a.nika: rustc expected Vec<_>, found &Vec<_> at return k):
struct P { items: Vec[i64] }
fn back(p: P) -> Vec[i64] {
let k = p.items
return k
}
fn main() {
let v = back(P { items: [1, 2, 3] })
print(v.len())
}It lowers to let k = &p.items; k. The let over a place is lent (ADR-094 D4), then handed back; nothing refuses the return (NK2106), nothing makes it a move.
To build:
let over a place escapes (a return, a push, a field, an argument the callee keeps), lower it as a move out of the place when the place’s owner is owned here (not ref) and is not read again. Otherwise refuse with the existing NK2106, saying what to write (.clone()). Decide from what hands_over and check_core_returns already record.tests/compiler/tests/, .nika + .stdout/.stderr): the probe runs and prints 3; the same through a push into a Vec[Vec[i64]]; a variant that reads p.items again after the let is refused (NK2106 .stderr); the same over a ref P parameter is refused.nikaia run scripts/where.nika -- NAME)crates/nikaia-std/src/tools/check_core_stmt.nika:307 (state.facts.lent_lets.insert), :314; check_binds.nika:68, 206; field in check_facts.nika:327.&: crates/nikaia-std/src/tools/emit_stmt.nika:465 and :519 (facts.lent_lets).hands_over tools/check_arm_leaves.nika:305; check_core_returns tools/check_core_leaves.nika:458.crates/nikaia/tests/it/handed_over.rs, tests/compiler/tests/let_lent_field_kept.*; spec Part III docs/specification/30-nikaia-tooling.md:1713.docs/builder-facts.md. Reproduce the probe, write the tests first..nika files above; target/fast/nikaia lower-std, cargo build --profile fast -p nikaia, commit the lowered/*.rs diff.nikaia test --both-settings --project tests/compiler, cargo test --profile fast -p nikaia --test it -- handed_over:: sysroot. Commit ... (Fixes #665).
Stop and report (Owner:) if the move-vs-refuse choice needs a spec change beyond Part III’s NK2106 text.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.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./home/user/Nikaia/docs/briefs/b665-lent-let-returned.md.report.md)Fields of docs/architect.md, Briefs and reports: Result: done|noop|partial|blocked (the bare word first; Owner: is a question for the owner or none, never a role), Files, Commit, Fixes, Pushed, Tests, Gate (green|red), Deviation, Found, Needs, Changelog, Owner, Disk freed. 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); how you solved your own step goes into the commit message. 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