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

Calculating dependencies ... done!
Dependency resolution took 1.02 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/pugixml-1.16::gentoo  USE="-test" 575 KiB
[ebuild  N     ] dev-util/wayland-scanner-1.26.0::gentoo  599 KiB
[ebuild  N     ] dev-libs/wayland-1.26.0::gentoo  USE="-doc (-selinux) -test" 0 KiB
[ebuild  N     ] dev-cpp/waylandpp-1.0.1-r1:0/1.0::gentoo  USE="-doc" 199 KiB

Total: 4 packages (4 new), Size of downloads: 1372 KiB