rust-bcder build-depends on librust-smallvec-0.6+default-dev, but
rust-smallvec is now at version 1.1 in unstable:

$ sudo apt build-dep rust-bcder
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 builddeps:rust-bcder : Depends: librust-smallvec-0.6+default-dev (>= 0.6.10-~~) but it is not installable
E: Unable to correct problems, you have held broken packages.
$

Please update rust-bcder for compatibility with the current
rust-smallvec.

We believe that the bug you reported is fixed in the latest version of
rust-bcder, 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 948632@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
James McCoy <jamessan@debian.org> (supplier of updated rust-bcder 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: Fri, 24 Jun 2022 23:45:49 -0400
Source: rust-bcder
Architecture: source
Version: 0.6.1-1
Distribution: unstable
Urgency: medium
Maintainer: Debian Rust Maintainers <pkg-rust-maintainers@alioth-lists.debian.net>
Changed-By: James McCoy <jamessan@debian.org>
Closes: 948632
Changes:
 rust-bcder (0.6.1-1) unstable; urgency=medium
 .
   * Package bcder 0.6.1 from crates.io using debcargo 2.5.0
     + Updates smallvec dependency to 1.x (Closes: #948632)
 .
   [ Sylvestre Ledru ]
   * Team upload.
   * Source upload
   * Package bcder 0.4.1 from crates.io using debcargo 2.4.4-alpha.0
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Files:
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