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

Calculating dependencies ... done!
Dependency resolution took 1.00 s (backtrack: 0/20).

[ebuild  N     ] dev-cpp/nlohmann_json-3.12.0-r1::gentoo  USE="-test" 9452 KiB
[ebuild  N     ] dev-cpp/cppdap-0_pre20240802::gentoo  USE="-test" 100 KiB

Total: 2 packages (2 new), Size of downloads: 9552 KiB