Miri gives warning: "warning: flag -Z doctest-xcompile has been stabilized in the 1.89 release, and is no longer necessary"

[theemathas]

With a mostly empty cargo project:

fn main() {}

[package]
name = "foo"
edition = "2024"

I ran cargo +nightly miri run, and I got the following output:

warning: flag `-Z doctest-xcompile` has been stabilized in the 1.89 release, and is no longer necessary
  Doctest cross-compiling is now always enabled.

   Compiling foo v0.0.0 (/Users/timch/foo)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.10s
     Running `/Users/timch/.rustup/toolchains/nightly-aarch64-apple-darwin/bin/cargo-miri runner target/miri/aarch64-apple-darwin/debug/foo`

The warning seems like a bug to me.

This is also reproducible when running on miri on the playground.

Rust versions:

$ rustc +nightly --version --verbose
rustc 1.89.0-nightly (777d37277 2025-05-17)
binary: rustc
commit-hash: 777d372772aa3b39ba7273fcb8208a89f2ab0afd
commit-date: 2025-05-17
host: aarch64-apple-darwin
release: 1.89.0-nightly
LLVM version: 20.1.4

$ cargo +nightly --version --verbose
cargo 1.89.0-nightly (47c911e9e 2025-05-14)
release: 1.89.0-nightly
commit-hash: 47c911e9e6f6461f90ce19142031fe16876a3b95
commit-date: 2025-05-14
host: aarch64-apple-darwin
libgit2: 1.9.0 (sys:0.20.0 vendored)
libcurl: 8.7.1 (sys:0.4.80+curl-8.12.1 system ssl:(SecureTransport) LibreSSL/3.3.6)
ssl: OpenSSL 3.4.1 11 Feb 2025
os: Mac OS 15.4.1 [64-bit]

Note the mismatch between the dates of the rustc and cargo release dates. However, rustup update seems to indicate that my rust installation is already up-to-date.

[RalfJung]

Yeah, I've seen this on our CI as well. We still haven't fully recovered from rust-lang/cargo#15462. A fix is in this repo and a sync is in progress -- but since it's just a warning, I won't push for landing that as fast as possible.