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

Calculating dependencies ... done!
Dependency resolution took 0.89 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by gnome-extra/gnome-contacts-49.0-r2::gentoo
# required by =gnome-extra/gnome-contacts-49.0-r2 (argument)
>=dev-libs/folks-0.15.12 eds
# required by gnome-extra/gnome-contacts-49.0-r2::gentoo[gnome-online-accounts]
# required by =gnome-extra/gnome-contacts-49.0-r2 (argument)
>=net-libs/gnome-online-accounts-3.58.1 vala

!!! The ebuild selected to satisfy "net-libs/gnome-online-accounts[vala]" has unmet requirements.
- net-libs/gnome-online-accounts-3.58.1::gentoo USE="-debug -gnome -gtk-doc -introspection -kerberos -ms365 -vala"

  The following REQUIRED_USE flag constraints are unsatisfied:
    vala? ( introspection )

(dependency required by "gnome-extra/gnome-contacts-49.0-r2::gentoo[gnome-online-accounts]" [ebuild])
(dependency required by "=gnome-extra/gnome-contacts-49.0-r2" [argument])