fix(async): linearize await inside an async-generator finally; fix aliased native-class new

[proggeramlug]

Lands #8736 and #8738.

#8736 — linearize await inside an async-generator finally (fixes #8715)

This closes the finally analog of the #8681 await-in-catch deadlock that #8707 fixed — and it is precisely the gap #8707's own new test surfaced when it was rebased onto main, which reported:

raw Expr::Await survived async-generator linearization (would block-wait at runtime):
  ["await-in-finally: 2 raw await(s) survived"]

At the time I held #8707 and flagged that resolving it meant deciding whether finally should route through its entry state the way catch now does. This is that decision, made properly: the linearizer already splits the finally into its own dispatch states with a finally_entry_state, and the async-step driver now routes through them, so a finally await lowers to a real microtask suspend rather than a blocking busy-wait.

async_generator_linearizes_every_await_position passes on the merged result — verified explicitly, since that test is what named the gap.

#8738 — aliased native-class import new no longer throws (fixes #8730)

An aliased ESM named import of a Node built-in class threw ReferenceError: identifier is not defined when constructed at module init:

import { BlockList as Wj4 } from "net";              new Wj4()
import { AsyncLocalStorage as J_z } from "async_hooks"; new J_z()
import { PassThrough as Lrz } from "stream";         new Lrz()

lower_new's alias-rewrite block rewrites the callee from the local import name to the class's export name, so the construction path matches the un-aliased form that codegen's builtin-New dispatch recognizes. This broke the natively-compiled Claude Code cli.js 2.1.112 bundle, which constructs all three at module init, so nearly every command crashed with an uncaught ReferenceError.

Validation (on the merged result)

• All 30 lint-job checkers pass
• perry-transform --lib: 93 passed, 0 failed
• perry-hir --lib: 334 passed, 0 failed
• perry-runtime --lib (RUST_TEST_THREADS=1): 2669 passed, 0 failed
• perry-codegen --lib: 1222 passed, 0 failed
• Squashed tree verified identical to the validated tree

Both PRs carried their own changelog.d/ fragments. No version bump.

Summary by CodeRabbit

• Bug Fixes

  • Fixed async generators becoming unresponsive when await is used inside a finally block during .return() or early loop termination.
  • Ensured asynchronous cleanup continues through microtasks without blocking execution.
  • Fixed aliased imports of native Node.js classes so constructors such as BlockList, AsyncLocalStorage, and PassThrough work correctly.

• Tests

  • Added coverage for async-generator cleanup scenarios and aliased native class construction.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 99882508-497d-466f-b008-1712b669b243

📥 Commits

Reviewing files that changed from the base of the PR and between c203c77 and 80fb6c5.

📒 Files selected for processing (6)

• changelog.d/8715-async-gen-finally-await.md
• changelog.d/8730-aliased-native-class-new-resolution.md
• crates/perry-hir/src/lower/expr_new.rs
• crates/perry-hir/tests/aliased_native_new_resolution.rs
• crates/perry-transform/src/async_to_generator_tests.rs
• crates/perry-transform/src/generator/lower.rs

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📝 Walkthrough

Walkthrough

The PR fixes async-generator .return() handling for awaits in finally blocks and native-module resolution for aliased Node built-in classes. It adds transform and lowering regression tests plus changelog entries.

Changes

Async-generator finally suspension

Layer / File(s)	Summary
Shared async-generator return routing crates/perry-transform/src/generator/lower.rs, crates/perry-transform/src/async_to_generator_tests.rs, changelog.d/8715-async-gen-finally-await.md	Async-generator .return() now resumes through __agstep. Await expressions in finally blocks suspend asynchronously. Synchronous generators retain local dispatch-loop handling. Tests cover combined try/finally, catch/finally, awaits, and yields.

Aliased native constructor resolution

Layer / File(s)	Summary
Native constructor lookup and regression coverage crates/perry-hir/src/lower/expr_new.rs, crates/perry-hir/tests/aliased_native_new_resolution.rs, changelog.d/8730-aliased-native-class-new-resolution.md	new lowering checks both the rewritten and original constructor identifiers in the native-module registry. Tests cover aliased Node built-in classes, unaliased imports, and unresolved constructors.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant AsyncGenerator
  participant __agstep
  participant FinallyAwait
  Caller->>AsyncGenerator: call .return()
  AsyncGenerator->>__agstep: route pending return as non-error resume
  __agstep->>FinallyAwait: execute finally state
  FinallyAwait-->>__agstep: suspend await on microtask queue
  __agstep-->>AsyncGenerator: complete or re-raise pending return
  AsyncGenerator-->>Caller: resolve .return()

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch merge/b29

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