regression(hir): ambient `declare function require` shadows the require intrinsic since #8343 — links against a nonexistent `require` symbol

[proggeramlug]

Since #8343 (6674f59, 2026-08-18), a module that carries the standard TypeScript ambient declaration

declare function require(name: string): any;
const fs = require("node:fs");

fails to link:

Undefined symbols for architecture arm64:
  "_require", referenced from: perry_fn_..._warmAndSummarize ...

Mechanism

1. A body-less declare function require(...) has always been registered as an external FFI declaration (register_imported_func) by lower_module_fn.rs — the generic "no body ⇒ extern" rule.
2. Before fix(cjs-wrap): stop HIR from dropping built-in require bindings in wrapped modules #8343 this was harmless for the const x = require("<builtin>") shape: the destructuring var-decl pass consumed the call into a native-module namespace binding before call lowering, so the FFI registration was never consulted.
3. fix(cjs-wrap): stop HIR from dropping built-in require bindings in wrapped modules #8343 added require_is_shadowed_by_local, which bails out of that destructuring path when lookup_imported_func("require") is Some — which the ambient declare makes true. The call now falls through to plain call lowering, resolves to the "imported func" require, and codegen emits a call to the symbol require, which no archive defines (it was always a compile-time intrinsic).

Blast radius: test-files/test_issue_8002_8003_thread_realm_caches.ts (COMPILE_FAIL in the 08-19 dispatch run 32298711372: compile-smoke red + one of parity's 27 compile_fails). Any user code using the ambient-declare idiom hits the same wall.

Fix direction: an ambient declare function require names the global intrinsic — it must not register as an FFI extern. #8343's CJS-wrap shadowing (a synthetic function require(...) with a body) is unaffected: that registers via register_func/locals, which correctly keeps shadowing.

Reproduced locally on a 0.5.1512 binary (macOS arm64); same failure as CI's Linux undefined reference to 'require'.