These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.56 s (backtrack: 0/20).

[ebuild  N     ] dev-lang/ocaml-4.14.2:0/4.14.2::gentoo  USE="ocamlopt -emacs -flambda -latex -xemacs" 5377 KiB
[ebuild  N     ] dev-ml/dune-3.23.1:0/3.23.1::gentoo  USE="-emacs -test" 3624 KiB
[ebuild  N     ] dev-ml/result-1.5:0/1.5::gentoo  USE="ocamlopt" 3 KiB
[ebuild  N     ] dev-ml/csexp-1.5.2-r1:0/1.5.2::gentoo  USE="ocamlopt -test" 12 KiB
[ebuild  N     ] dev-ml/dune-configurator-3.21.1:0/3.21.1::gentoo  USE="ocamlopt" 3352 KiB
[ebuild  N     ] sci-libs/gsl-2.7.1-r3:0/27::gentoo  USE="deprecated -cblas-external -static-libs" 7346 KiB
[ebuild  N     ] dev-ml/gsl-ocaml-1.24.3-r2::gentoo  USE="ocamlopt" 99 KiB

Total: 7 packages (7 new), Size of downloads: 19808 KiB

WARNING: One or more updates/rebuilds have been skipped due to a dependency conflict:

dev-lang/ocaml:0

  (dev-lang/ocaml-5.5.1:0/5.5.1::gentoo, ebuild scheduled for merge) USE="ocamlopt -emacs -flambda -latex -test -xemacs" conflicts with
    <dev-lang/ocaml-5 required by (dev-ml/gsl-ocaml-1.24.3-r2:0/0::gentoo, ebuild scheduled for merge) USE="ocamlopt"
    ^               ^