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

Calculating dependencies ... done!
Dependency resolution took 2.86 s (backtrack: 12/20).

[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/findlib-1.9.8::gentoo  USE="ocamlopt -doc -tk" 269 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/sexplib0-0.16.0:0/0.16.0::gentoo  USE="ocamlopt" 22 KiB
[ebuild  N     ] dev-ml/ppx_derivers-1.2.1:0/1.2.1::gentoo  USE="ocamlopt" 3 KiB
[ebuild  N     ] dev-ml/result-1.5:0/1.5::gentoo  USE="ocamlopt" 3 KiB
[ebuild  N     ] dev-ml/num-1.6-r1::gentoo  USE="ocamlopt" 67 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/stdlib-shims-0.3.0::gentoo  USE="ocamlopt" 10 KiB
[ebuild  N     ] dev-ml/ppxlib-0.30.0-r2:0/0.30.0::gentoo  USE="ocamlopt -test" 561 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     ] dev-ml/base-0.16.3-r1:0/0.16::gentoo  USE="ocamlopt" 433 KiB
[ebuild  N     ] dev-ml/parsexp-0.16.0:0/0.16::gentoo  USE="ocamlopt" 56 KiB
[ebuild  N     ] dev-ml/ppx_here-0.16.0:0/0.16::gentoo  USE="ocamlopt" 5 KiB
[ebuild  N     ] dev-ml/ppx_sexp_conv-0.16.0-r2:0/0.16::gentoo  USE="ocamlopt" 66 KiB
[ebuild  N     ] dev-ml/ppx_sexp_message-0.16.0:0/0.16::gentoo  USE="ocamlopt" 9 KiB
[ebuild  N     ] dev-ml/sexplib-0.16.0-r1:0/0.16::gentoo  USE="ocamlopt" 54 KiB
[ebuild  N     ] dev-ml/ppx_log-0.16.0:0/0.16::gentoo  USE="ocamlopt" 7 KiB

Total: 20 packages (20 new), Size of downloads: 14128 KiB

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

dev-ml/sexplib0:0

  (dev-ml/sexplib0-0.17.0-r2:0/0.17::gentoo, ebuild scheduled for merge) USE="ocamlopt" conflicts with
    =dev-ml/sexplib0-0.16*:=[ocamlopt] required by (dev-ml/sexplib-0.16.0-r1:0/0.16::gentoo, ebuild scheduled for merge) USE="ocamlopt"
    ^                ^^^^^            
    =dev-ml/sexplib0-0.16*:=[ocamlopt] required by (dev-ml/base-0.16.3-r1:0/0.16::gentoo, ebuild scheduled for merge) USE="ocamlopt"
    ^                ^^^^^            

dev-ml/ppxlib:0

  (dev-ml/ppxlib-0.39.0:0/0.39.0::gentoo, ebuild scheduled for merge) USE="ocamlopt -test" conflicts with
    <dev-ml/ppxlib-0.36.0 required by (dev-ml/ppx_sexp_conv-0.16.0-r2:0/0.16::gentoo, ebuild scheduled for merge) USE="ocamlopt"
    ^              ^^^^^^

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-0.30.0-r2:0/0.30.0::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
dev-ml/findlib:0