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

Calculating dependencies ... done!
Dependency resolution took 0.97 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/rapidjson-1.1.0_p20250205::gentoo  USE="-doc -examples -test" 1091 KiB
[ebuild  N     ] dev-libs/cereal-1.3.2-r4::gentoo  USE="-doc -test" 377 KiB

Total: 2 packages (2 new), Size of downloads: 1468 KiB