typing/perf 7: owning env meet — quadratic clone elimination (chains −22–28%) - #86
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typing/perf 7: owning env meet — quadratic clone elimination (chains −22–28%)#86Felipe705x wants to merge 1 commit into
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… fast path New lattice-op counters (vt_meets, vt_joins, env_bindings_copied) localized the remaining cost precisely: - chains do ZERO VariableType meets — their cost was env cloning: every Concat cloned the accumulated environment, O(vars) String-key clones per hop, quadratic along a chain (272 copies for chain_16); - subq/optional shapes spend their time in real meet/join walks over rich refined types (22–44 per check) — targeted next, not here. Changes: - TypeEnvironment::meet_owned consumes the left env (Concat/Join/ match-chain/subquery folds own their accumulator). Merged bindings stage in a scratch Vec applied on success; the Err path hands the environment back untouched, preserving the exact keep-previous-env-on-error behavior. meet(&,&) remains as the cloning wrapper. - warn_for_collapsed_bindings walked all merged keys; only SHARED keys can collapse (one-sided keys pass through meet untouched, so their "empty" was pre-existing and the old walk skipped them — its one-sided message arms were unreachable). Now takes the stashed shared bindings, warnings byte-identical. - TypeEnvironment::union: Rc::ptr_eq fast path when both arms hold the same shared binding (join(v,v) collapses to v) — common since both arms get the same refine-cache Rc. Idle-machine medians vs M06: - chain_16 64.2 → 46.4 us (−28%) chain_8 28.3 → 22.1 us (−22%) - chain_dir_16 73.4 → 55.1 us (−25%) anydir_8 54.1 → 40.5 us (−25%) - union_8 59.0 → 50.0 us (−15%) - subq_exists / multi_optional unchanged (their cost is the lattice meets; that is the next milestone) - chk/parse: chains now 2.7–4.1× Full sweep 80 targets green. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Stacked on #85.
New lattice-op counters first localized the cost: chains do zero type meets — they were paying quadratic env cloning (272 String-key copies for chain_16, every Concat re-cloning the accumulator). Subquery/OPTIONAL shapes spend their time in genuine meet/join walks instead (44 for multi_optional); those are the next milestone's target and deliberately untouched here.
TypeEnvironment::meet_ownedconsumes the left env; scratch-staged merge keeps the error path's exact keep-previous-env behavior.warn_for_collapsed_bindingsnow iterates only shared keys — provably the only keys that can collapse (the old walk's one-sided arms were unreachable); warnings byte-identical.uniongets anRc::ptr_eqfast path (both arms usually hold the same refine-cacheRc;join(v,v) = v).vs #85: chain_16 64 → 46 µs, chain_dir_16 73 → 55 µs, anydir_8 54 → 41 µs, union_8 59 → 50 µs; subq shapes unchanged by design. Chains now sit at 2.7–4.1× parse cost.
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