fix(proxy): Array.prototype methods on a Proxy-wrapped array (#5196)

[proggeramlug]

Fixes #5196.

Problem

A generic Array.prototype method (map, reduce, forEach, filter, join, sort, …) called on a Proxy-wrapped array either threw TypeError: Cannot convert undefined or null to object or SIGSEGV'd. Individual proxy traps worked; the array-method-on-proxy path did not.

const arr = new Proxy([1, 2, 3] as number[], { get(t, k, r) { return Reflect.get(t, k, r); } });
console.log(arr.map((x) => x * 10).join(",")); // expected 10,20,30

Two distinct gaps:

1. HIR — arr.<method>(...) on a proxy local was eagerly folded into dense Expr::Array* nodes (ArrayReduce/ArrayForEach/ArrayJoin/…) that dereference the proxy id as a real ArrayHeader → SIGSEGV. map/filter/find only escaped by luck via the is_class_instance gate (a proxy local is typed Named("Proxy")), which is why the reported map case threw rather than crashed.
2. codegen — that escaped map case lowered to Call{callee: ProxyGet} and fell through to the plain closure-call path, losing the this receiver, so the method ran with this = undefined.

Fix

• local_array_methods.rs — skip the array fast path entirely for proxy locals (ctx.proxy_locals), so all methods route uniformly through the proxy member-call path.
• proxy_reflect.rs + lower_call/mod.rs — new try_lower_proxy_method_call: route proxy.method(args) (non call/apply) through js_native_call_method, whose Proxy arm binds this to the proxy.
• native_call_method.rs — the Proxy arm short-circuits the non-mutating Array methods to the spec-generic array-like engine, whose al_get/al_length already route element/length reads through the proxy get trap. This gives correct semantics and avoids the depth-guard recursion the generic Get→Call fused path would hit on a built-in method value.
• generic.rs + array/mod.rs — extracted the array-like dispatch table as dispatch_arraylike_read_method so both the proto-chain path and the proxy path share it.

Verification

• Repro now prints 10,20,30.
• A broad 14-method test (incl. a value-transforming get trap) is byte-identical to node --experimental-strip-types.
• Normal (non-proxy) arrays unaffected; existing fused proxy object-method calls (fix(runtime): route symbol-keyed reads on a Proxy through the get trap #4661) and call/apply (runtime: implement Proxy apply/construct trap dispatch #3656) still pass.
• perry-runtime (1041 pass) and perry-hir (full suite) green. The lone builtin_prototype_methods_reject_dynamic_new failure is a known parallel-flake (passes isolated); the commander::args manifest-drift failure is pre-existing on main.

Out of scope

Spreading a proxy array [...pa] still SIGSEGVs — that's the iterator-protocol (Symbol.iterator) path, independent of array-method dispatch and untouched here. Worth a separate follow-up.

No changelog entry or version bump (maintainer folds those in at merge).

Summary by CodeRabbit

• New Features

  • Added support for calling methods on proxy objects (e.g., proxy.method(args)).

• Bug Fixes

  • Fixed recursion depth-guard failures when calling array-like methods on proxy-wrapped arrays, improving reliability of array method operations on proxies.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: efe1ac89-b023-4148-85ed-c8f69901d929

📥 Commits

Reviewing files that changed from the base of the PR and between f6faf2c and 4822477.

📒 Files selected for processing (6)

• crates/perry-codegen/src/expr/proxy_reflect.rs
• crates/perry-codegen/src/lower_call/mod.rs
• crates/perry-hir/src/lower/expr_call/local_array_methods.rs
• crates/perry-runtime/src/array/generic.rs
• crates/perry-runtime/src/array/mod.rs
• crates/perry-runtime/src/object/native_call_method.rs

🚧 Files skipped from review as they are similar to previous changes (6)

• crates/perry-hir/src/lower/expr_call/local_array_methods.rs
• crates/perry-codegen/src/lower_call/mod.rs
• crates/perry-runtime/src/array/mod.rs
• crates/perry-runtime/src/object/native_call_method.rs
• crates/perry-codegen/src/expr/proxy_reflect.rs
• crates/perry-runtime/src/array/generic.rs

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📝 Walkthrough

Walkthrough

Fixes Array.prototype method calls on Proxy-wrapped arrays by extracting a shared dispatch_arraylike_read_method runtime helper, adding a Proxy fast-path in js_native_call_method, inserting an HIR guard to bypass the dense array fast-path for proxy locals, and emitting js_native_call_method for ProxyGet(p, method) call sites in codegen.

Changes

Proxy array method call dispatch

Layer / File(s)	Summary
dispatch_arraylike_read_method helper and re-exports crates/perry-runtime/src/array/generic.rs, crates/perry-runtime/src/array/mod.rs	Introduces dispatch_arraylike_read_method as a public function routing non-mutating Array.prototype method names to js_arraylike_* implementations, returning None for unsupported names. try_array_proto_chain_method delegates to it; the function is re-exported from array/mod.rs.
Proxy fast-path in js_native_call_method crates/perry-runtime/src/object/native_call_method.rs	Inside the Proxy branch of js_native_call_method, inserts an early dispatch via dispatch_arraylike_read_method with refreshed_args(), returning immediately when handled before the existing Proxy Get→Call recursion path.
HIR proxy guard and codegen lowering crates/perry-hir/src/lower/expr_call/local_array_methods.rs, crates/perry-codegen/src/expr/proxy_reflect.rs, crates/perry-codegen/src/lower_call/mod.rs	Adds a proxy_locals guard in try_local_array_methods that returns Ok(Err(args)) to bypass the dense array fast-path for proxy-wrapped locals. Introduces try_lower_proxy_method_call in proxy_reflect.rs to emit js_native_call_method for ProxyGet(p, method) call sites, wired as an early branch in lower_call.

Sequence Diagram(s)

sequenceDiagram
  actor Source as JS Source
  participant lower_call
  participant try_lower_proxy_method_call
  participant js_native_call_method
  participant dispatch_arraylike_read_method

  Source->>lower_call: proxy.map(fn) call site
  lower_call->>try_lower_proxy_method_call: callee=ProxyGet(proxy, "map"), args=[fn]
  try_lower_proxy_method_call-->>lower_call: emits js_native_call_method(proxy, "map", args)
  lower_call->>js_native_call_method: proxy + "map" + args at runtime
  js_native_call_method->>dispatch_arraylike_read_method: object=proxy, method="map", refreshed_args
  dispatch_arraylike_read_method-->>js_native_call_method: Option<f64> result
  js_native_call_method-->>Source: mapped array value

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• PerryTS/perry#5194: Also modifies try_local_array_methods to bypass the array fast-path and defer to js_native_call_method for certain Array.prototype calls, using the same Ok(Err(args)) fallthrough pattern.

Poem

🐇 A proxy array called map one day,
But the runtime just threw it away.
Now a fast-path is set,
No recursion to fret—
The mapped values hop happily away! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main fix: enabling Array.prototype methods on Proxy-wrapped arrays.
Description check	✅ Passed	The description comprehensively documents the problem, the multi-layer fix, verification results, and scope boundaries, fully meeting template requirements.
Linked Issues check	✅ Passed	All code changes directly address the linked issue #5196: the fix enables Array.prototype methods to work correctly on Proxy-wrapped arrays by addressing gaps in both HIR and codegen layers.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing array method dispatch on proxies; spreading a proxy array is explicitly noted as out of scope and deferred to a separate follow-up.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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