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

Calculating dependencies ... done!
Dependency resolution took 1.07 s (backtrack: 0/20).

[ebuild  N     ] net-libs/udns-0.6::gentoo  USE="ipv6 tools" 84 KiB
[ebuild  N     ] dev-cpp/nlohmann_json-3.12.0-r1::gentoo  USE="-test" 9452 KiB
[ebuild  N     ] net-libs/libtorrent-0.15.7::gentoo  USE="-debug -test" 852 KiB
[ebuild  N     ] net-p2p/rtorrent-0.15.7::gentoo  USE="-debug -lua (-selinux) -test -tinyxml2 -xmlrpc" LUA_SINGLE_TARGET="-lua5-3 -lua5-4" 847 KiB

Total: 4 packages (4 new), Size of downloads: 11234 KiB