Merge train: #9561 (forEach live-index squeeze defer) - #9563
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September 2, 2026 21:15
…tead of shifting the walk #9504 made the array-like `map[i]` / `set[i]` read a live-index accessor: it squeezes tombstones so raw index == live index and never hands out a hole. `forEach` walks the raw entries with a counter that the delete-path squeeze defers around (the walk registers itself) — but the accessor's squeeze had no such guard. A callback that deleted already-visited entries and then read `map[j]` compacted the buffer under the walk's counter, shifting the survivors below it: with two earlier entries deleted, two later ones were never visited (18 of 20, Map and Set). While a walk is active the accessor now defers the squeeze exactly as the delete path does and resolves the live index by stepping over the tombstones (O(idx), on a path that is rare by construction); the outermost walk's completion performs the deferred squeeze as before. Outside a walk the accessor squeezes as #9504 specified, and #9504's `a_tombstoned_collection_never_hands_a_hole_to_an_indexed_read` stays green. The for…of fast path is unaffected: its cursor rebases through the compaction log (#9513), so a squeeze under it was already exact. Found by the automated review on #9513, reproduced on merged main. Tests: `a_live_index_read_inside_foreach_defers_the_squeeze_and_skips_nothing` for Map and Set (every entry visited once; live values read mid-walk; layout left alone during the walk, squeezed on completion; the accessor still squeezes outside a walk) and `test_gap_foreach_live_index_read_no_skip.ts` (single and nested walks), node-differential. perry-runtime 3018 passed / 0 failed (release, single-threaded); #9504's and #9513's fixtures still match node; cargo fmt --all --check clean; no clippy warning in the touched files.
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Lands #9561 (a live-index
map[i]/set[i]read inside an active forEach walk defers the squeeze instead of compacting under the walk counter — closes the hole #9513's review found) rebased onto main.Validation: release build green; RUST_TEST_THREADS=1 perry-runtime 3021/0; new fixture and the #9513 multi-delete fixture both byte-identical to node; lint gates green.
Rebase-merge preserving authorship.