Rust: couldn't create a temp dir: Operation not permitted

[lambdasierra]

Checklist

• I have checked existing issues for potential duplicates before creating this one.
• I have read the [Troubleshooting guide][].
• I have read https://emacs.stackexchange.com/questions/28429/how-do-i-troubleshoot-emacs-problems

Bug description

When running Flycheck on a Rust source file, an error message like the following is displayed in the minibuffer:

couldn't create a temp dir: Operation not permitted (os error 1) at path "/dev/rmetaG2wOVY"

In Rust versions 1.64.0 and later, rustc -o /dev/null fails when it tries to create temporary files in the /dev directory; see rust-lang/rust#111157

Flycheck uses -o /dev/null to avoid creating binaries when checking, reported in #1497 and fixed in #1501.

Steps to reproduce

• Install Rust 1.64.0 or later

• Create a file named main.rs with the following contents:

fn main() {
    println!("Hello, world!");
}

• Launch Emacs with emacs -Q

• Evaluate the following in the *scratch* buffer:

(require 'package)

(add-to-list 'package-archives
             '("MELPA Stable" . "https://stable.melpa.org/packages/") t)

(package-refresh-contents)

(package-install 'rust-mode)

(package-install 'flycheck)

(global-flycheck-mode)

• Open the file main.rs in Emacs

• The minibuffer shows an error message like the following.

couldn't create a temp dir: Operation not permitted (os error 1) at path "/dev/rmetaG2wOVY"

System configuration

Syntax checkers for buffer main.rs in rust-mode:

First checker to run:

  rust
    - may enable: yes
    - predicate:  t
    - executable: Found at /opt/homebrew/bin/rustc

Checkers that are compatible with this mode, but will not run until properly configured:

  rust-cargo (disabled)
    - may enable:  Automatically disabled!
    - predicate:   t
    - executable:  Found at /opt/homebrew/bin/cargo
    - Cargo.toml:  Missing
    - Crate type:  lib
    - Binary name: Not required

  rust-clippy (disabled)
    - may enable: Automatically disabled!
    - predicate:  t
    - executable: Found at /opt/homebrew/bin/cargo
    - Clippy:     Cannot find the `cargo clippy' command
    - Cargo.toml: Missing

Flycheck Mode is enabled.  Use C-u C-c ! x to enable disabled
checkers.

--------------------

Flycheck version: 32
Emacs version:    29.1
System:           aarch64-apple-darwin21.6.0
Window system:    ns

Emacs configuration:

• Plain Emacs / Custom configuration

Additional notes

This doesn't happen every time Flycheck runs. For example, creating a new file and running flycheck-buffer does not trigger it. I can consistently reproduce it by opening a Rust source file that already exists.

[bbatsov]

@flycheck/rust Can someone take a look?