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agent: builder model: opus max_turns: 90 budget_usd: 18 effort: medium —

Brief: #1158 an inner match on an arm-bound name that takes a non-copy part lowers to ref x / match *x

Blocks: the comptime_run move (M1, #125): ComptimeRan cannot carry CheckWall.

Score: a defect, specified behaviour (taking a part of a value bound by value moves it), rustc rejects the lowered code (E0507). Found by the M1 builder (2026-11-02).

Facts: Where things live, Traps already met, Commands

Problem

The probe is verbatim in #1158 (run it with target/fast/nikaia run): match r { Ran::Hit(wall) => match wall { Wall::Refused { detail } => detail, ... } } lowers to Ran::Hit(ref wall) => match *wall { ... }, which rustc refuses with E0507. let w = wall; match w lowers correctly. Suspect: check_compare.nika parts_lent / check_core_flow_lent_parts: the inner match taking a part does not count as giving wall away.

To build

1. An inner match that takes a non-copy part of an arm-bound name gives that name away, so the outer arm binds by value. Test tests/compiler/inner_match_takes_arm_bound_part.nika + .stdout. Commit Fixes #1158. Run the tests your change touches (nikaia test on the new test, the --test it filters of the files you change); lower-std and its fixpoint if a tools/*.nika changed.

Rules

• Read .claude/agents/builder.md and docs/builder-facts.md first. Commit locally with target/fast/nikaia run scripts/commit.nika -- REPORT; the driver pushes.
• Version lines, CHANGELOG.md, badges and NK codes are the supervisor’s.
• No cause after about 60 turns: stop, Result: partial with what you ruled out and the suspected file and function.

Report (at most 15 lines, to exactly /home/user/Nikaia/docs/briefs/bugs/b38-1158-inner-match-takes-arm-name.md.report.md)

Fields of docs/supervisor.md, Briefs and reports. Final answer, one line: done <sha>, report <path> (or BLOCKED: ...).

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