Thank you, Ludovic, for your attention.
That exact. New try gave acceptable result. And now I am able to keep trying to configure touchpad tap... https://lists.gnu.org/archive/html/help-guix/2018-10/msg00137.html

# guix pull
Updating channel 'guix' from Git repository at 'https://git.savannah.gnu.org/git/guix.git'...
Building from this channel:
  guix      https://git.savannah.gnu.org/git/guix.git    a961ae4
Computing Guix derivation for 'x86_64-linux'... |
The following derivations will be built:
   /gnu/store/n3bclgnpk15cg1ldsv06yk6ad6p8wnqj-profile.drv
   /gnu/store/xvfzdgdm1633m2yj5p66yzm9jjd3inzp-config.scm.drv
...
...
New in this revision:
  9 new packages: emacs-clang-format, emacs-gtk-look, fstrcmp,
    python-pyelftools, r-aggregation, r-destiny, r-h5, r-savr, xmlrpc-c
  14 packages upgraded: crossguid@0.0-2.fef89a4,
    guile-newt@0-1.4eaa3cf84, java-ngs@2.9.3, kodi@18.0b5, ncbi-vdb@2.9.3,
    ngs-sdk@2.9.3, python-ilinkedlist@0.3.1, r-minimal@3.5.1, r@3.5.1,
    rmath-standalone@3.5.1, sra-tools@2.9.3, tadbit@0.2.0, vsearch@2.9.1,
    wxmaxima@18.10.1

# guix describe
Generation 29    Nov 09 2018 20:08:09    (current)
  guix a961ae4
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: a961ae469cf81797df34f22eef0f0f5ca1a21e07

9. Nov 2018 19:39 by ludo@gnu.org:

Hello!

<znavko@tutanota.com> skribis:
I watch an issue. Trying to roll-back and choose another kernel in grub I have no changes. Guix says 'Wrong type to upply: #t'

This has been fixed a couple of days ago in commit
ea68b3f6527cf4a02c554cf3f6f446e30f4940f6.

(Note that ‘guix pull’ was successful, despite the backtrace.)

Sorry for the mess!

Ludo’.