No, I'm sure that isn't right.
> Didn't find any other examples. At the moment rust code is recognized
> as ASCII C program text.
>
> Index: usr.bin/file/magdir/rust
> ===================================================================
> RCS file: usr.bin/file/magdir/rust
> diff -N usr.bin/file/magdir/rust
> --- /dev/null 1 Jan 1970 00:00:00 -0000
> +++ usr.bin/file/magdir/rust 14 Jan 2019 12:20:22 -0000
> @@ -0,0 +1,5 @@
> +#------------------------------------------------------------------------------
> +# rust: file(1) magic for Rust language
> +#
> +0 search fn\ main()\ { Rust program text
> +
