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 dev-ruby/ruby-vips-2.3.0::gentoo
# required by =dev-ruby/ruby-vips-2.3.0 (argument)
>=media-libs/vips-8.18.7 introspection

!!! The ebuild selected to satisfy "media-libs/vips:0/42[introspection]" has unmet requirements.
- media-libs/vips-8.18.7::gentoo USE="fontconfig highway jpeg jpeg2k png tiff -archive -deprecated -doc -exif -fftw -fits -graphicsmagick -heif -imagemagick -imagequant -introspection -jpegxl -lcms -matio -openexr -orc -pango -pdf -raw -svg -test -vala -webp"

  The following REQUIRED_USE flag constraints are unsatisfied:
    fontconfig? ( pango )

  The above constraints are a subset of the following complete expression:
    doc? ( introspection ) fontconfig? ( pango ) graphicsmagick? ( imagemagick ) test? ( jpeg png webp ) vala? ( introspection )

(dependency required by "dev-ruby/ruby-vips-2.3.0::gentoo" [ebuild])
(dependency required by "=dev-ruby/ruby-vips-2.3.0" [argument])