frontend: same-module enum referenced before its declaration resolves to 0 (silent miscompile)

[proggeramlug]

Summary

An enum declared in a module but referenced before its textual declaration
(valid TypeScript — enum bindings are module-scoped) is treated as an unknown
global. Member reads lower to 0 and the compiler emits:

Warning: unknown identifier '<Enum>' — assuming global; member access will
dispatch by name at runtime, bare reads lower to 0

This is a silent miscompile: the binary links but the enum value is wrong.

Minimal repro

function tag(): First { return First.B; }   // used before declaration
enum First { A = "A", B = "B", C = "C" }
console.log("fwd:", tag());

$ perry run fwd_enum.ts
  Warning: unknown identifier 'First' — assuming global; member access will
  dispatch by name at runtime, bare reads lower to 0
fwd: 0

Expected

fwd: B

Notes

• Moving the enum declaration above its first use makes it work, confirming
  it's a resolution/hoisting-order problem, not an enum-value problem.
• Found in the wild at scale: zod declares ZodFirstPartyTypeKind near the end
  of zod/src/v3/types.ts and references it earlier throughout the file. Compiling
  zod emits ~90 of these warnings, so zod's internal type-kind dispatch (which
  compares against ZodFirstPartyTypeKind.*) is silently corrupted even once it
  otherwise compiles.
• May share a root cause with runtime/hir: closure assigning to a forward-declared module-level var loses the write (var hoisting) #4450 (closure write to a forward-declared
  module-level binding is lost) — both look like hoisting/forward-reference
  resolution gaps.

Environment

perry 0.5.1122 · macOS arm64 · native host target.

[andrewtdiz]

Taking this as part of a TS enum lowering PR cut with #4509.\n\nIntended scope: same-module enum forward references plus numeric enum reverse mappings, with focused parity/regression fixtures for both silent miscompile shapes. Non-goals: unrelated class/codegen issues, async lowering, and broader module/global hoisting semantics beyond enum declarations.

[andrewtdiz]

Opened PR #4517 for the TypeScript enum lowering cut: #4517

This covers same-module enum forward references from functions declared before the enum, and is batched with #4509 because both failures share the same enum metadata/runtime-object lowering path.