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02 Adapters: Decrement on Discard

With Section 01 complete, every yielded element is owned (+1 RC). Adapters that discard elements (filter rejections, skip’s N elements) must now dec them to prevent leaks. Adapters that pass through elements (take, chain, enumerate) already have correct ownership — the element flows from source to consumer unchanged. Adapters that produce new elements (map, flat_map) already yield owned values.

02.1 Filter: Dec Rejected Elements

File: compiler/ori_rt/src/iterator/next.rs — next_filtered (lines 157-172)

Currently, rejected elements are read into a scratch buffer and silently discarded when the loop re-advances. With owned elements, these must be dec’d.

  • Add elem_dec_fn: Option<extern "C" fn(*mut u8)> to IterState::Filtered variant in state.rs

  • Update ori_iter_filter in adapters.rs to accept and store elem_dec_fn

  • In next_filtered: after predicate returns false, call elem_dec_fn(scratch.as_mut_ptr()) on the rejected element

  • TDD: AOT test — [1,2,3,4,5].iter().filter(x -> x % 2 == 0).collect() with str elements, verify zero leaks

  • Codegen update (Section 04): emit_iter_filter must pass get_or_generate_elem_dec_fn(elem_ty)

  • Subsection close-out (02.1) — MANDATORY before starting 02.2:

    • All tasks above are [x] and behavior verified
    • Update this subsection’s status in section frontmatter to complete
    • Run /improve-tooling retrospectively on THIS subsection
    • Run /sync-claude on THIS subsection — check whether code changes invalidated any CLAUDE.md, .claude/rules/*.md, or canon.md claims. If no API/command/phase changes, document briefly. Fix any drift NOW.
    • Repo hygiene check — run diagnostics/repo-hygiene.sh --check and clean any detected temp files.

02.2 Skip: Dec Skipped Elements

File: compiler/ori_rt/src/iterator/next.rs — next_skip (lines 191-206)

Same pattern as filter. Skipped elements are read into scratch and discarded.

  • Add elem_dec_fn: Option<extern "C" fn(*mut u8)> to IterState::SkipN variant in state.rs

  • Update ori_iter_skip in adapters.rs to accept and store elem_dec_fn

  • In next_skip: after each skipped element, call elem_dec_fn(scratch.as_mut_ptr())

  • TDD: AOT test — ["a","b","c","d"].iter().skip(count: 2).join(separator: ",") with str elements, verify zero leaks

  • Codegen update (Section 04): emit_iter_skip must pass get_or_generate_elem_dec_fn(elem_ty)

  • Subsection close-out (02.2) — MANDATORY before starting 02.3:

    • All tasks above are [x] and behavior verified
    • Update this subsection’s status in section frontmatter to complete
    • Run /improve-tooling retrospectively on THIS subsection
    • Run /sync-claude on THIS subsection — check whether code changes invalidated any CLAUDE.md, .claude/rules/*.md, or canon.md claims. If no API/command/phase changes, document briefly. Fix any drift NOW.
    • Repo hygiene check — run diagnostics/repo-hygiene.sh --check and clean any detected temp files.

02.3 Cycle and Rev: Storage Ownership

Files: adapters.rs (ori_iter_cycle, ori_iter_rev), next.rs (next_cycled, next_reversed)

These adapters eagerly collect elements into a Vec<u8> buffer. With owned elements:

  • cycle: First pass stores owned elements into buffer (they were yielded as +1 from source). Buffer now owns them. On replay passes, the buffer yields copies — these need inc (same as list yields). Add elem_inc_fn to IterState::Cycled.

  • rev: Collects all elements into Vec<u8>, drops source. Elements in the Vec are owned. When yielding backward, the bytes are copied out — but since the Vec will be freed, no additional inc needed (transfer semantics). Verify the Vec cleanup path calls elem_dec_fn for remaining elements if iteration terminates early (break/take).

  • TDD: AOT tests for cycle + rev with str elements under leak check

  • Subsection close-out (02.3) — MANDATORY before starting 02.4:

    • All tasks above are [x] and behavior verified
    • Update this subsection’s status in section frontmatter to complete
    • Run /improve-tooling retrospectively on THIS subsection
    • Run /sync-claude on THIS subsection — check whether code changes invalidated any CLAUDE.md, .claude/rules/*.md, or canon.md claims. If no API/command/phase changes, document briefly. Fix any drift NOW.
    • Repo hygiene check — run diagnostics/repo-hygiene.sh --check and clean any detected temp files.

02.4 Pass-Through Adapters: Verify

Adapters: take, chain, enumerate, zip, flatten, flat_map

These adapters do not discard elements — they pass them through from source to consumer. With owned elements from Section 01, the ownership flows naturally.

  • take: passes through first N elements, then stops. Source’s remaining elements are cleaned up by the source’s Drop (which already handles RC). No change needed. Verify.

  • chain: passes through all elements from first then second. Ownership flows from each source. No change needed. Verify.

  • enumerate: wraps element in (index, element) tuple. The element’s ownership transfers into the tuple. No change needed. Verify.

  • zip: concatenates bytes from two sources. Both sources yield owned elements. The zip output tuple owns both. No change needed. Verify.

  • flatten: yields elements from nested iterators. Inner iterators yield owned elements. No change needed. Verify.

  • flat_map: composition of map + flatten. Both already handle ownership. No change needed. Verify.

  • Subsection close-out (02.4) — MANDATORY before starting Section 03:

    • All tasks above are [x] and behavior verified
    • Update this subsection’s status in section frontmatter to complete
    • Run /improve-tooling retrospectively on THIS subsection
    • Run /sync-claude on THIS subsection — check whether code changes invalidated any CLAUDE.md, .claude/rules/*.md, or canon.md claims. If no API/command/phase changes, document briefly. Fix any drift NOW.
    • Repo hygiene check — run diagnostics/repo-hygiene.sh --check and clean any detected temp files.

02.R Third Party Review Findings

  • None.

02.N Completion Checklist

  • Filter and skip adapters correctly dec discarded elements
  • Cycle correctly handles first-pass storage and replay inc
  • Rev correctly handles collected element cleanup
  • All pass-through adapters verified (no change needed)
  • timeout 150 ./test-all.sh green
  • timeout 150 ./clippy-all.sh green
  • /commit-push
  • /tpr-review passed
  • /impl-hygiene-review passed
  • /improve-tooling section-close sweep