Code

I tried this code:
https://github.com/FlixCoder/fhir-sdk

cargo build -p fhir-model --release

(Probably the same as creating a crate with dependency fhir-model from crates.io).

The example crate is huge and difficult to navigate, so I tried to reproduce with a minimal example with the same cycle:

#[derive(Debug, PartialEq)] pub struct Bundle(pub Box<BundleInner>); #[derive(Debug, PartialEq)] pub struct BundleInner { pub issues: Option<Resource>, pub entry: Vec<Option<BundleEntry>>, } #[derive(Debug, PartialEq)] pub struct BundleEntry { pub resource: Option<Resource>, } #[derive(Debug, PartialEq)] pub enum Resource { Bundle(Bundle), }

However, this successfully compiles.. So I don't really know how to proceed from here, I am open to suggestions what we could try to find a better small example.

I expected to see this happen: Code compiles with opt-level > 1

Instead, this happened: Compilation error on opt-level > 1

(See FlixCoder/fhir-sdk#56 )

Version it worked on

It most recently worked on: 1.89

Version with regression

Rust 1.90 does not and rustc 1.92.0-nightly (975e6c8 2025-09-23) also does not work.

rustc --version --verbose:

rustc 1.92.0-nightly (975e6c8fe 2025-09-23) binary: rustc commit-hash: 975e6c8fec280816d24fbde6b8dfe19620f2efe6 commit-date: 2025-09-23 host: x86_64-unknown-linux-gnu release: 1.92.0-nightly LLVM version: 21.1.1 

Backtrace

No crash, no backtrace.