From ci.debian.net:

329s autopkgtest [05:59:06]: test rust-test-case-core-3:@: [-----------------------
329s debian cargo wrapper: options, profiles, parallel, lto: ['parallel=48'] [] ['-j48'] 0
329s debian cargo wrapper: rust_type, gnu_type: x86_64-unknown-linux-gnu, x86_64-linux-gnu
329s debian cargo wrapper: linking /usr/share/cargo/registry/* into /tmp/tmp.mlAiIsVnBA/registry/
329s debian cargo wrapper: options, profiles, parallel, lto: ['parallel=48'] [] ['-j48'] 0
329s debian cargo wrapper: rust_type, gnu_type: x86_64-unknown-linux-gnu, x86_64-linux-gnu
329s debian cargo wrapper: running subprocess (['env', 'RUST_BACKTRACE=1', '/usr/bin/cargo', '-Zavoid-dev-deps', 'test', '--profile', 'release', '--verbose', '--verbose', '-j48', '--target', 'x86_64-unknown-linux-gnu', '--config', 'profile.release.debug-assertions=true', '--config', 'profile.release.overflow-checks=true', '--config', 'profile.release.panic="unwind"', '--lib', '--bins', '--examples', '--all-features'],) {}
329s error: failed to select a version for the requirement `syn = "^2.0"`
329s candidate versions found which didn't match: 3.0.9, 1.0.109
329s location searched: directory source `/tmp/tmp.mlAiIsVnBA/registry` (which is replacing registry `crates-io`)
329s required by package `test-case-core v3.3.1 (/usr/share/cargo/registry/test-case-core-3.3.1)`
329s note: perhaps a crate was updated and forgotten to be re-vendored?
329s autopkgtest [05:59:06]: test rust-test-case-core-3:@: -----------------------]

https://ci.debian.net/packages/r/rust-test-case/testing/amd64/76956858/

The current rust-test-case expects syn 2.0 which is no longer in debian. This also causes testing failures in other packages that wish to use test-case. Please update the dependency to syn 3.0 or package new test-case 3.4 which has this fix upstream.

Yes, it does. The problem is that rust-test-case's debian/control
(Build-)Depends against librust-syn-dev rather than the
librust-syn-2-dev that aligns with Cargo.toml.

Cheers,

* James McCoy (jamessan@debian.org) wrote:

Ah yes fair, I thought for some reason librust-syn-2-dev had already
been removed from the archive.

Quoting James McCoy (2026-10-22 01:45:56)

Right - I had attempted to make the frequent version migrations easier
by relaxing dependencies, but was unaware that the Rust team also
deviates from common Debian logics in how unversioned provisions are
used.

I am now tightening dependencies again whenever I make package updates.

Am working on the test-case crate now.

 - Jonas

We believe that the bug you reported is fixed in the latest version of
rust-test-case, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1151585@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Jonas Smedegaard <dr@jones.dk> (supplier of updated rust-test-case package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Thu, 22 Oct 2026 08:23:11 +0200
Source: rust-test-case
Architecture: source
Version: 3.4.0+ds-1
Distribution: unstable
Urgency: medium
Maintainer: Jonas Smedegaard <dr@jones.dk>
Changed-By: Jonas Smedegaard <dr@jones.dk>
Closes: 1151585
Changes:
 rust-test-case (3.4.0+ds-1) unstable; urgency=medium
 .
   [ upstream ]
   * new release;
     closes: bug#1151585, thanks to Eric Dorland
 .
   [ Jonas Smedegaard ]
   * update watch file:
     + capitalize file format field label
     + stop set auto-mangling of upstream version (now done by default)
     + limit to STABLE_VERSION
   * bump project versions in virtual packages and autopkgtests
   * update patches
   * tighten (build-, autopkgtest-)dependencies
   * use debhelper compatibility level 14 (not 13)
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 62b857dbd30d96235eacbd8fedf6645cff2ea695 5656 rust-test-case_3.4.0+ds-1.debian.tar.xz
 a4d6661a1a6d22894d5fe5319168b5394d5987e2 18654 rust-test-case_3.4.0+ds-1_amd64.buildinfo
Checksums-Sha256:
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Files:
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