[Bug]: Unreachable when lowering typedef

[pgoodman]

VAST version

08c665f

LLVM version

17.0.4

Operating system

macOS

Description

Crash when trying to look up a typedef. Might be an out-of-order issue, where the codegen visitor comes across a forward declaration of a function, but then hops "down" to the definition, skipping over many as-of-yet unseen declarations. Then, it goes and codegens the function body, and comes across a case where it needs a typedef (typedef void (*curl_free_callback)(void *ptr);), but in jumping down to the function, it has skipped over the TypedefDecl, and thus hasn't generated an operation for it, and so it fails to resolve the typedef, leading to an unreachable error.

Curl_bufq_pass.c.zip

Steps to Reproduce

Run on the attached file.