Also I did not install rust by myself:

# guix package --list-installed | grep rust
#

Mar 28, 2019, 4:43 AM by znavko@tutanota.com <mailto:znavko@tutanota.com>:

> Hello! I ran `guix system reconfigure /etc/config.scm` and now rust is compiling. Rust is compiling too long.
>
> I've produced `guix graph --type=reverse-package rust | dot -Tsvg > r.svg` to see why does guix do this, but there is no answer.
>
> My config and rust reverse dependecies tree are in attach.
> A tree has only one node - rust. 
>
>