agent: builder model: sonnet max_turns: 90 budget_usd: 15 —

Brief: #655 step 4a, two statements on one line are a parse error

Score: bugs lane (docs/priorities.md): S=3 (the parser accepts println!("hi") as two statements; a reader and a model are both misled), O=small, C~3 M (b655 step 3 run), area parser.

Issue text (#655, item 3 first half, step 4)

println!("hi") parses as two statements, println and !"hi", and 1 2 on one line parses too. To build 4: two expressions on one line are a parse error. Tests.

Probe (architect, 252bcf2, `target/fast/nikaia check t.nika`)

fn main() {\n println!("hi")\n} and fn main() {\n let a = 1 2\n} both print Checked t.nika. Wanted: a parse error at the second statement, saying a statement begins a line.

Decision (architect; specification text to add with the build)

Add to Part I 3.1 (docs/specification/10-nikaia-light.md, after the first code block, ~line 919), verbatim:

A statement begins a line. Two statements on one line are a parse error: println!("hi") is not println and then !"hi", and let a = 1 2 is not let a = 1 and then 2. The first statement of a block may stand on the line of its { ({ return 0 }), and a jump’s trailing condition (return 0 if done) is part of its statement. No new NK code: it is a parse error like the others (no code).

Locations

crates/nikaia/src/parser/mod.rs: rule stmt_list (2245, stmts:stmt*), rule stmt (2248); the helper same_line (180) and Trivia::began_a_line (153) already answer “is this token at the start of a line” (ADR-135 D3). Make every statement after the first in stmt_list require that it begins a line (a negated same_line, or a new new_line helper beside it, consuming nothing).
Check tools/*.nika, examples/, tests/, packages/ still parse: target/fast/nikaia lower-std (see builder-facts) and the test runs below. Code of ours that writes two statements on one line is rewritten onto two lines in the same commit (that is the fix, not a workaround).

To build

The parser change and the spec sentence above.
Tests in tests/compiler/tests/: two_statements_on_one_line_are_refused.nika + .stderr (the 1 2 probe), a_bang_after_a_name_is_not_a_second_statement.nika + .stderr (the println! probe), and a_statement_may_follow_its_brace.nika + .stdout (if true { println("a") } and return 0 if x on one line run). Run: cargo test --profile fast -p nikaia --test it -- parse, target/fast/nikaia test --both-settings --project tests/compiler. Commit Part of #655 (steps 1, 2, 4b, 5 stay open). Changelog: a statement begins a line; two on one line are a parse error (Part I 3.1).

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

Read 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).
Before pushing: cargo fmt, cargo clippy --all-targets -- -D warnings, scripts/pre-push-check.sh, and the gate of .claude/agents/builder.md (#852).
No version lines, CHANGELOG.md, badges; no new NK code. New tests in Nikaia only; never the full suite. No foreground sleep, no polling; scripts in files.
Disk: 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.

Report (at most 15 lines, to exactly `/home/user/Nikaia/docs/briefs/b655-one-statement-a-line.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. Deviation: is only a step of the brief built otherwise than written or not built; 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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