regression(hir): Coop's Next.js fixture throws nameless ReferenceError: identifier is not defined at init on 0.5.1519 — loaded on 0.5.1516 #8882

Summary

The Coop Next.js benchmark fixture (a production next build --webpack App Route compiled through Coop, benchmarks/next-small in PerryTS/coop) loads and serves on Perry 0.5.1516 (3885ba491) — that is the build every #8546 measurement was taken on — and on 0.5.1519 (41e8479a5) it dies at module init, before any request:

daemon: ReferenceError: identifier is not defined
daemon:     at <anonymous>

One application is enough; this is not the multi-heap case. Coop's daemon exits during preload with status 1, so #8546 cannot currently be reproduced on main at all.

What it is not

• Not regression(hir): natively-compiled cli.js throws nameless "identifier is not defined" at init — new <minified-local>() scope-resolution miss #8730's new <minified-local>() class. fix(async): linearize await inside an async-generator finally; fix aliased native-class new #8739 is in this build, and the compile's "unknown identifier — assuming global" list for the whole bundle contains only genuine browser globals: window ×112, location ×30, document ×20, __REACT_DEVTOOLS_GLOBAL_HOOK__ ×12, cookieStore ×6, define ×4, __non_webpack_require__ ×2. Nothing that resolves to a local.
• Not the bundle drifting: it is built from source by scripts/prepare-next-benchmark.sh on every run, and the bundler is asserted (webpack-runtime.js present, no [turbopack]_runtime.js).

Where the throw can come from

The message is the nameless form (js_throw_reference_error_unresolved_get). Its HIR emitters on 41e8479a5:

• crates/perry-hir/src/lower_decl/helpers.rs:189, 204, 214, 218 (and the _unresolved_assignment sibling at 197)
• crates/perry-hir/src/lower/expr_new.rs:1599

Between 3885ba491 and 41e8479a5 (127 commits) the HIR commits that touch binding/scope resolution are the first suspects:

• e2eee4048 fix(hir): share function and var declaration bindings (fix(hir): share function and var declaration bindings #8753)
• 98ecdc582 fix(hir): resolve the Web Streams global constructor (fix(hir): resolve the Web Streams global constructor #8795)
• 726f6e96e perf: static method literals, captured closure reuse, argument shape facts (perf: static method literals, captured closure reuse, argument shape facts #8796)
• 8a55a26f1 land perf: complete ECS benchmark specializations #8833: ECS specializations, with the argument-route guard restored (land #8833: ECS specializations, with the argument-route guard restored #8837)

Reproduction

PerryTS/coop main at 3e7180e (pin 0.5.1519, rust-toolchain.toml = nightly-2026-08-20):

scripts/build-perry-libraries.sh
cargo build --release -p coop-daemon -p coop-worker
scripts/prepare-next-benchmark.sh            # next build --webpack, then the daemon compiles it (see the compile-time issue: budget with COOP_NEXT_COMPILE_TIMEOUT)
APP=$(find target/next-benchmark/coop-run/compiled/next-bench -name app.dylib | head -1)
COOP_BENCH_APP_COUNTS=1 COOP_BENCH_EXECUTION_MODE=in_process COOP_BENCH_APP_LIBRARY="$APP" \
  cargo test --release -p coop-daemon --test resource_benchmark measure_in_process_startup_and_rss -- --ignored --nocapture

Same steps with perry-main.lock at 3885ba491 load the application (the #8546 runs).

The ask, again

#8730 asked for it and it is still the blocker for this class: name the identifier in the message. at <anonymous> with no name means the only way to attribute this is to instrument the five throw sites and recompile the bundle, which for this fixture is a multi-hour build on 0.5.1519. A name would make it a two-minute bisect.