Merge train 204: dependency group, store-plan cache, builder fold, GC shape borrow, ambient declare (v0.5.1582)

[proggeramlug]

This train lands six PRs as v0.5.1582. They touch no file in common and all six cherry-picked clean.

• ci(deps): bump taiki-e/install-action from 2.87.3 to 2.87.8 #10312 — taiki-e/install-action 2.87.3 → 2.87.8 (CI action, SHA-pinned).
• deps(deps): bump the cargo-minor-and-patch group across 1 directory with 12 updates #10314 — the cargo minor-and-patch group, 12 updates cascading to 99 lockfile version lines.
• perf(object): vet the store-plan cache per key, not per receiver #10346 — perf(object): vet the store-plan cache per key, not per receiver.
• fix(hir): fold a builder whose stores are separated from its {} (#10353) #10355 — fix(hir): fold a builder whose stores are separated from its {} (codegen: a property store from a constant-valued local loses Ptr<Shape> promotion (75x) #10353).
• perf(gc): borrow the shape record in the slot visitor, stop moving the iterator (#10362) #10371 — perf(gc): borrow the shape record in the slot visitor, stop moving the iterator (perf(gc): on a retained object graph perry is 8.5× node — 13 minors at ~0.8G instructions each (measured on #10352) #10362).
• fix(hir): an ambient declare const/let/var binds nothing (#10363) #10374 — fix(hir): an ambient declare const/let/var binds nothing (hir: declare const/let/var is lowered as a real binding initialized to undefined — shadows the global it describes #10363).

Eight source commits, each verified to preserve its authorship. No train repairs were needed — all four crates/-touching PRs shipped their own changelog.d/ fragment, and every gate passed as assembled.

One patch-id differs and the reason is recorded in train204r-source-proof.json: #10314's commit touches only Cargo.lock, its added and removed lines are byte-identical to the source, and only the surrounding context moved because main advanced the workspace version line inside the same region. git patch-id hashes context alongside the hunk body, so an unmodified edit replayed onto a moved base yields a different id. No content change.

Validation

Validated head 06c5249840, on main 99363beb1a. Five-package release build pinned and hash-verified; artifacts_match_pin true after the suites and again after the gap phase.

• All nine preflight gates pass, including both the raw-handle and unrooted-local-shape ratchets against main.
• Crate suites: codegen 1,563 · runtime 3,970 · standard library 139 · HIR 419 · transform 137 · CLI 1,139. The runtime suite's only failure is main's known release-only gc::tests::heap_generation::a_free_or_move_outside_every_scope_is_caught_in_debug_builds.
• The three integration suites the diff names: builder_fold_gap, builder_fold_gap_semantics, descriptor_store_fast_paths — all pass.
• Lint 82 of 83; the only failure is Public benchmark evidence freshness.

Gap: filters object, store, builder, declare, shape, iterator, descriptor. Seven fixtures diverge. Three were newly checked here by compiling and running each under both the main and train compilers, with Node as a third reference; all three behave identically on the two arms:

Fixture	Node	main	train
test_issue_3580_arguments_object_semantics	rc=0	rc=0	rc=0, identical
test_issue_4034_object_literal_semantics	rc=1	rc=0	rc=0, identical
test_issue_927_jwt_verify_returns_object	rc=1	rc=0	rc=0, identical

Those three were checked hardest because #10346 changes the store-plan cache and jwt_verify sits downstream of #10314's crypto bumps — an object fixture failing on this train is exactly where a real regression would hide.

The A/B asserts build provenance from the binaries themselves: each compiled arm must carry exactly one git:<sha> stamp and it must be that arm's pin (d0e99ea92b for main, 06c5249840 for the train). A PERRY_RUNTIME_DIR that does not resolve falls through to real archives silently, so without this an arm can measure a build that was never made and report a confident, wrong green.

The remaining four are previously attributed: test_gap_iterator_prototype_next_patch (failing on main since the commit that added it — see below), test_issue_7981_thread_shape_stamp_parent (perry-only; Node cannot resolve perry/thread), test_three_like_native_class_descriptors (Node exits 1), and test_issue58_object_string (prints Date.now() elapsed; the same binary varies run to run).

A note on main's long-standing gap failures

Three fixtures the snapshot expects to PASS have been failing on main for over a week and are not caused by this train or any recent one. They were bisected today, per fixture rather than per shard:

• test_gap_iterator_prototype_next_patch — never passed. Added already failing by 8a73d9f80a, the commit that introduced prototype_next_is_canonical. Perry returns raw values where Node returns patched ones, so the fast path misreads a patched prototype. A correctness claim with no passing evidence behind it.
• test_gap_disposablestack_2875 — last passed 87dc33492, first failed 43200e9d4 (34 commits).
• test_gap_2899_2779_2777_static_helpers — last passed 43200e9d4, first failed 7651a36c3 (107 commits); grouped values come back null.

Before merging, the pushed head and unchanged main are checked again. After merging, the rewritten commits are checked for preserved authorship and the main tree must match the validated train exactly.

Summary by CodeRabbit

• New Features

  • Ambient declare const, let, and var declarations no longer create runtime bindings; references resolve to global values as expected.
  • Special platform constants continue to behave as compile-time values.

• Bug Fixes

  • Object-building code now preserves correct execution order while avoiding unnecessary performance slowdowns.
  • Property stores continue to invoke own accessors and enforce descriptor restrictions correctly.

• Performance

  • Improved property-store performance for objects with descriptors.
  • Reduced garbage-collection overhead during shape and slot processing.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 4f978384-96ac-4c3b-80ce-91af541baa64

📥 Commits

Reviewing files that changed from the base of the PR and between 99363be and 06c5249.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (30)

• .github/workflows/coverage.yml
• CLAUDE.md
• Cargo.toml
• changelog.d/10287-store-plan-per-key.md
• changelog.d/10355-builder-fold-gap.md
• changelog.d/10371-gc-slot-iterator-memcpy.md
• changelog.d/10374-ambient-declare-binds-nothing.md
• crates/perry-hir/src/lower/ambient.rs
• crates/perry-hir/src/lower/builder_fold.rs
• crates/perry-hir/src/lower/expr_function.rs
• crates/perry-hir/src/lower/fn_ctor_env.rs
• crates/perry-hir/src/lower/lower_module_fn.rs
• crates/perry-hir/src/lower/lowering_context.rs
• crates/perry-hir/src/lower/mod.rs
• crates/perry-hir/src/lower/module_decl.rs
• crates/perry-hir/src/lower/module_decl/namespace.rs
• crates/perry-hir/src/lower/stmt.rs
• crates/perry-hir/src/lower/tests.rs
• crates/perry-hir/src/lower/tests/ambient_declare.rs
• crates/perry-hir/src/lower_decl/block.rs
• crates/perry-hir/src/lower_decl/block/var_names.rs
• crates/perry-hir/src/lower_decl/body_stmt.rs
• crates/perry-hir/tests/builder_fold_gap.rs
• crates/perry-runtime/src/gc/layout.rs
• crates/perry-runtime/src/gc/layout_slot_visit.rs
• crates/perry-runtime/src/object/field_set_by_name/tail.rs
• crates/perry-runtime/src/object/gc_slots.rs
• crates/perry-runtime/src/object/shapes.rs
• crates/perry/tests/builder_fold_gap_semantics.rs
• crates/perry/tests/descriptor_store_fast_paths.rs

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📝 Walkthrough

Walkthrough

The pull request changes TypeScript ambient declaration lowering, object builder folding, GC shape handling, and descriptor-aware store plans. It adds focused HIR, runtime, and integration tests, updates changelog entries, bumps the workspace version, and updates the coverage action pin.

Changes

Ambient declaration lowering

Layer / File(s)	Summary
Ambient declaration contract and lowering crates/perry-hir/src/lower/ambient.rs, crates/perry-hir/src/lower/stmt.rs, crates/perry-hir/src/lower/lower_module_fn.rs, crates/perry-hir/src/lower/lowering_context.rs	Ordinary ambient declarations no longer create runtime bindings. Their names are recorded for global lookup. __platform__ and __plugins__ retain compile-time constant shapes.
Ambient scope and export registration crates/perry-hir/src/lower/expr_function.rs, crates/perry-hir/src/lower/fn_ctor_env.rs, crates/perry-hir/src/lower/module_decl.rs, crates/perry-hir/src/lower/module_decl/namespace.rs, crates/perry-hir/src/lower_decl/*	Hoisting, capture, namespace, export, block, and function-constructor scans skip ambient bindings.
Ambient declaration validation crates/perry-hir/src/lower/tests/ambient_declare.rs, crates/perry-hir/src/lower/tests.rs	Tests cover global resolution, exports, namespaces, closures, Annex B behavior, TDZ handling, and compile-time constants.

Builder fold gap handling

Layer / File(s)	Summary
Gap detection and safety checks crates/perry-hir/src/lower/builder_fold.rs, changelog.d/10355-builder-fold-gap.md	The builder fold scans up to 64 statements and accepts only inert, hoistable gaps for empty object literals.
Gap-aware fold application crates/perry-hir/src/lower/builder_fold.rs	The fold moves the allocation below skipped statements while preserving their order and value evaluation order.
Builder fold validation crates/perry-hir/tests/builder_fold_gap.rs, crates/perry/tests/builder_fold_gap_semantics.rs	Tests cover foldable and blocked gaps, populated literals, TDZ behavior, evaluation order, and object semantics.

GC shape-record handling

Layer / File(s)	Summary
Shape-record handle and lookup crates/perry-runtime/src/object/shapes.rs, changelog.d/10371-gc-slot-iterator-memcpy.md	GC carrier paths can retain borrowed ShapeRecordRef handles instead of copied ShapeDescriptor values.
GC layout propagation crates/perry-runtime/src/gc/layout.rs, crates/perry-runtime/src/object/gc_slots.rs	GC layout and slot-range helpers pass borrowed shape records through shared-mask, object-field, array, and closure paths.
GC iterator copy reduction crates/perry-runtime/src/gc/layout_slot_visit.rs	The masked payload scan iterates by reference, avoiding an iterator copy per traced object.

Per-key store-plan eligibility

Layer / File(s)	Summary
Per-key store-plan gate crates/perry-runtime/src/object/field_set_by_name/tail.rs, changelog.d/10287-store-plan-per-key.md	Own descriptors no longer reject store plans for every key. The gate and plan-recording path check whether the specific key is covered.
Descriptor dispatch validation crates/perry/tests/descriptor_store_fast_paths.rs	A warmed plan is tested against own accessors, non-writable descriptors, and key ordering.

Release metadata

Layer / File(s)	Summary
Version and workflow updates Cargo.toml, CLAUDE.md, .github/workflows/coverage.yml	The workspace version changes to 0.5.1582, and the coverage workflow pin changes to taiki-e/install-action v2.87.8.

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Other · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant Source
  participant HIRLowerer
  participant LoweringContext
  participant GlobalLookup
  Source->>HIRLowerer: declare const/let/var
  HIRLowerer->>LoweringContext: record erased ambient name
  HIRLowerer-->>Source: emit no runtime binding
  Source->>GlobalLookup: reference ambient name
  GlobalLookup-->>Source: resolve by global lookup

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✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch train204r

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