On Sun, Jul 11 2021, southerntofu via Guix-patches via wrote:

> ---
>  gnu/packages/crates-io.scm | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/gnu/packages/crates-io.scm b/gnu/packages/crates-io.scm
> index 2ac7bc0c2e..d3641af193 100644
> --- a/gnu/packages/crates-io.scm
> +++ b/gnu/packages/crates-io.scm
> @@ -13721,6 +13721,29 @@ from macros.")
>          ("rust-rustc-serialize" ,rust-rustc-serialize-0.3)
>          ("rust-strsim" ,rust-strsim-0.5))))))
>  
> +(define-public rust-downcast-0.10
> +  (package
> +    (name "rust-downcast")
> +    (version "0.10.0")
> +    (source
> +      (origin
> +        (method url-fetch)
> +        (uri (crate-uri "downcast" version))
> +        (file-name
> +          (string-append name "-" version ".tar.gz"))
> +        (sha256
> +          (base32
> +            "07bh0l95gwrzak6rj29v8kkm577d8vivxsxhqgscf64b4bq59d2b"))))
> +    (build-system cargo-build-system)
> +    (arguments `(#:skip-build? #t))
> +    (home-page
> +      "https://github.com/fkoep/downcast-rs")
> +    (synopsis
> +      "Trait for downcasting trait objects back to their original types")
> +    (description
> +      "Trait for downcasting trait objects back to their original types")

Likewise (full sentence).