`rustc` hang in Rust for Linux

[ojeda]

(Using the new trait solver does not make it hang anymore. I guess it may be a well-known issue with the old one, but I decided to file it for reference.)

I tried this code:

trait Bound {}

trait Alloc {
    const OPS: u32;
}

trait Driver {
    type Object<Ctx: Bound>: Alloc;
}

fn f<T: Driver>() -> u32 {
    T::Object::OPS
}

I expected to see this happen: a compile error.

Instead, this happened: the compiler hangs or gets OOM-killed.

Live: https://godbolt.org/z/e166xq4qo

Original report: https://rust-for-linux.zulipchat.com/#narrow/channel/291565-Help/topic/Do.20we.20have.20anyone.20for.20helping.20triage.20rust.20tooling.20bugs.3F/near/600770020

Meta

rustc --version --verbose:

rustc 1.98.0-nightly (e7815e522 2026-06-04)

It also triggers in e.g. current stable (1.96.0).

[ojeda]

@rustbot label A-rust-for-linux

[theemathas]

Note: the code is invalid because it doesn't specify the Ctx type.