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

Calculating dependencies ... done!
Dependency resolution took 1.57 s (backtrack: 0/20).

[ebuild     U  ] dev-util/spirv-headers-1.4.363.0::gentoo [1.4.341.0::gentoo] 581 KiB
[ebuild  N     ] dev-util/vulkan-headers-1.4.363.0::gentoo  USE="-test" 3337 KiB
[ebuild     U  ] dev-util/spirv-tools-1.4.363.0::gentoo [1.4.341.0::gentoo] USE="-test" 3474 KiB
[ebuild  N     ] dev-util/glslang-1.4.363.0:0/16.6::gentoo  4528 KiB
[ebuild  N     ] media-gfx/vkBasalt-0.3.2.10::gentoo  329 KiB

Total: 5 packages (2 upgrades, 3 new), Size of downloads: 12246 KiB