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

Calculating dependencies ... done!
Dependency resolution took 1.58 s (backtrack: 2/20).

[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/ocaml-compiler-libs-0.12.4-r2:0/0.12.4::gentoo  USE="ocamlopt" 6 KiB
[ebuild  N     ] dev-ml/ocaml-migrate-parsetree-2.4.0-r1:0/2.4.0::gentoo  USE="ocamlopt -test" 203 KiB
[ebuild  N     ] dev-ml/sexplib0-0.17.0-r2:0/0.17::gentoo  USE="ocamlopt" 23 KiB
[ebuild  N     ] dev-ml/stdlib-shims-0.3.0::gentoo  USE="ocamlopt" 10 KiB
[ebuild  N     ] dev-ml/ppx_derivers-1.2.1:0/1.2.1::gentoo  USE="ocamlopt" 3 KiB
[ebuild  N     ] dev-ml/ppxlib-0.22.2-r4:0/0.22.2::gentoo  USE="ocamlopt -test" 199 KiB

Total: 8 packages (8 new), Size of downloads: 9441 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/ocaml-migrate-parsetree-2.4.0-r1:0/2.4.0::gentoo, ebuild scheduled for merge) USE="ocamlopt -test"
    ^               ^
    <dev-lang/ocaml-5 required by (dev-ml/ppxlib-0.22.2-r4:0/0.22.2::gentoo, ebuild scheduled for merge) USE="ocamlopt -test"
    ^               ^


!!! The following update(s) have been skipped due to unsatisfied dependencies
!!! triggered by backtracking:

dev-ml/ocaml-compiler-libs:0