fix(hir): new <class value>() no longer folds builtin-named user methods to the Array fast path (#11128)

[proggeramlug]

Fixes #11128

Problem

A user method whose name matches an Array builtin (push, pop, shift, unshift, splice, sort, indexOf, slice, join, map, ...) was never called when the receiver was built by new from a class value. That covers a const C: any = R, a factory's return value, and a destructured require(...) namespace. redis@6.1.0's linked-list.js hits this: s.push(1); s.length gives 0.

Root cause

infer_type_from_expr typed new C() as Type::Named("C") whenever C was an identifier. That included identifiers that are only value bindings. Named("C") names no class, interface or function constructor, so type_is_class_instance answered false. The array gate in local_array_methods.rs then took "not a string" as proof of an array, and r.push(1) lowered to Expr::ArrayPush. ArrayPush writes a fresh array back into the receiver local, so the user method never ran. r became an array, and every later call on it went wrong too (get/has returned {}). The same thing happened for new C<T>(), via Generic { base: "C" }.

A declared x: InstanceType<typeof R> parameter had the same result by a different route: its type Generic { base: "InstanceType" } was not recognised as a class instance, so it folded to the array fast path too.

Fix (HIR only)

• lower_types.rs: new C() / new C<T>() now types the instance Any when C resolves to a local value binding. That excludes class declarations (including const Foo = class {}, which is in classes_index), function declarations and imports. Any already declines every name-keyed fast path, and runtime dispatch still runs the real Array/Map/Set method when the value really is one.
• local_array_methods.rs / array_only_methods.rs: Generic { base: "InstanceType" } counts as a class instance and is never treated as a proven array.

Proven arrays keep their path unchanged. The emitted LLVM IR for an array-push microbench is byte-identical between the two arms.

Validation (perrymaster, perry-dev, PERRY_NO_AUTO_OPTIMIZE=1, Node 26.5.1 at /opt/node-v26.5.1-linux-x64)

• New gap test test-files/test_gap_user_method_builtin_name_dynamic_ctor.ts (45 lines of output). It calls 22 colliding method names through any, factory, destructured-namespace, member-ctor, field, let, InstanceType-param, interface-typed and fn-return receivers. Controls: typed receivers, plus a real Array/Map/Set reached through an any constructor.
  • main (784ed8e): fails. When the file is run in sections, 4 of 6 differ from node: any-local, factory, require-shape and other-bindings. Sections 4 and 5 are the typed and real-builtin controls, and they match. Section 3 prints exactly what the issue reported (length 0, shift undefined).
  • this branch: byte-identical to node.
• New HIR test crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs (7 tests): 5 fail on main sources and all 7 pass on the branch. Two controls check that a proven number[] and new Array() still lower to ArrayPush/ArrayPop.
• Real package: @redis/client@6.1.0 dist/lib/client/linked-list.js was compiled through compilePackages. SinglyLinkedList now matches node (s.length 1, s.shift 1 0), where main gives 0 / undefined. EmptyAwareSinglyLinkedList then throws "Cannot initialize a private field twice" on both arms. That is Subclass field initializer 'new events_1()' with a private-field parent throws 'Cannot initialize a private field twice' (blocks redis createClient) #11120, fixed by fix(codegen): stage no ancestor field initializers a delegated constructor installs itself (#11120) #11129, and is outside this PR.
• Gap A/B, compiler vs compiler: 142 array / method / dispatch / class-expression / ctor gap tests. Each arm ran with its own self-consistent perry + runtime archives. This was a compile-and-diff loop against node, because harness port 17891 was held by another sweep. Results: 137 PASS/PASS, 1 FAIL→PASS (the new test), 1 FAIL/FAIL (test_gap_console_methods, timer values only), 3 CFAIL/CFAIL (ext-wrapper tests that need target/release ext archives in this setup). There are no regressions.
• cargo test --profile perry-dev -p perry-hir -p perry-codegen: 2965 passed, 0 failed. The new HIR suite also passes (7/7).
• cargo check -p perry-hir --all-targets (dev profile): no warnings.
• cargo fmt --all -- --check: OK. scripts/check_file_size.sh: OK.
• SKIP_COMPILE_GATES=1 scripts/run_lint_gates.sh: 87 of 88 script gates passed; the compile tier was not run. The one failure is cargo xwin check, because cargo-xwin is not installed on the host. This PR touches no runtime or stdlib code.

Perf (instruction counts, perf stat -e instructions:u, 5 runs each, medians)

The microbench is a proven number[] push loop plus a declared-class push, at two iteration counts. Both arms emit byte-identical LLVM IR for the program. The linked binaries still differ, because each arm links its own separately built runtime archive, and the remaining instruction delta is at the noise level.

N	main	this PR
2M	966,877,254	966,896,315
6M	2,916,536,382	2,916,443,551
6M − 2M	1,949,659,128	1,949,547,236 (−0.006 %, noise)

The package-audit measurement mutex script (mlock.sh) was not present on the host, so these counts were taken without it. The IR identity is the load-bearing evidence here.

Not run / not covered

• The full gap sweep and the auto-optimize mode were not run. Only the 142-test compile-and-diff A/B above was.
• cargo test --workspace was not run.
• Separate pre-existing defect, not fixed here: an interface declared inside a block or function body is erased without being registered, so it is not treated as an interface. A receiver typed with it ({ interface P { push(...) } const q: P = new C(); q.push(1) }) still folds to ArrayPush. Module-level interfaces work. The gap test declares its interface at module scope for that reason.

Summary by CodeRabbit

• Bug Fixes
  • Corrected method dispatch for instances created from dynamically bound constructors. Methods that share names with built-in array methods now invoke the instance’s own behavior unless the receiver is known to be an array.
  • Preserved built-in array behavior for actual arrays and the optimized handling of statically typed array methods.

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📒 Files selected for processing (3)

• crates/perry-hir/src/lower_types.rs
• crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs
• test-files/test_gap_user_method_builtin_name_dynamic_ctor.ts

🚧 Files skipped from review as they are similar to previous changes (3)

• crates/perry-hir/src/lower_types.rs
• crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs
• test-files/test_gap_user_method_builtin_name_dynamic_ctor.ts

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📝 Walkthrough

Walkthrough

Constructor expressions that use local value bindings now infer as Any, including when a function declaration shares the name. InstanceType receivers skip array-method fast paths. HIR and runtime tests cover colliding method names and controls for proven arrays and builtin instances.

Changes

Dynamic constructor method dispatch

Layer / File(s)	Summary
Dynamic constructor inference crates/perry-hir/src/lower_types.rs, crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs, changelog.d/11137-dynamic-ctor-builtin-named-methods.md	Local value bindings used as constructors infer as Any, including when an outer function has the same name. HIR tests cover dynamic constructor forms and declared-class, function, import, and Array controls.
Array-fold receiver checks crates/perry-hir/src/lower/expr_call/array_only_methods.rs, crates/perry-hir/src/lower/expr_call/local_array_methods.rs, crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs	The receiver checks treat InstanceType generics as class instances. HIR tests cover InstanceType receivers and preserve array fast paths for proven arrays.
Runtime regression scenarios test-files/test_gap_user_method_builtin_name_dynamic_ctor.ts	Runtime scenarios exercise user methods whose names collide with builtin methods across dynamic constructor forms and other bindings. Controls cover typed class instances and native Array, Map, and Set behavior.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Merge Risk: ⚪ Minimal · up to 71817

The changed dispatch paths preserve calls to user methods, and the regression test checks their effects and returns. No identified issue prevents merging after normal checks.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 65.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 20 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main HIR fix: preventing dynamic constructor instances from incorrectly using Array fast paths for user methods with builtin names.
Description check	✅ Passed	The description provides a detailed problem statement, root cause, implementation summary, related issue, validation results, performance data, and known limitations. It does not follow the repository…
Linked Issues check	✅ Passed	Issue [#11128] requires user-defined methods on instances created from dynamic class values to preserve effects and return values, including names such as push. The lowering change infers new from…
Out of Scope Changes check	✅ Passed	The changes remain within the coding scope of [#11128]. Factory results, destructured namespace members, class shadowing, and InstanceType receivers exercise the same dynamic-constructor dispatch de…

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Actionable comments posted: 1

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Inline comments:
In `@crates/perry-hir/src/lower_types.rs`:
- Around line 628-629: Update the local-binding guard near `lookup_func` and
`lookup_imported_func` so an active `lookup_local` binding takes precedence over
outer function or imported-function bindings; remove those exclusions while
preserving the class check. Add a regression test where an inner `const C`
shadows an outer `function C`, and verify `new C<number>()` dispatches
array-method calls such as `push` to the local constructor’s instance rather
than lowering them as array operations.

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📒 Files selected for processing (6)

• changelog.d/11137-dynamic-ctor-builtin-named-methods.md
• crates/perry-hir/src/lower/expr_call/array_only_methods.rs
• crates/perry-hir/src/lower/expr_call/local_array_methods.rs
• crates/perry-hir/src/lower_types.rs
• crates/perry-hir/tests/dynamic_ctor_builtin_method_names.rs
• test-files/test_gap_user_method_builtin_name_dynamic_ctor.ts

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[proggeramlug]

Landed on main in merge train 271 (#11145, v0.5.1654).