Gem::DependencyList#why_not_ok?

# File tmp/rubies/ruby-3.2.0/lib/rubygems/dependency_list.rb, line 117
def why_not_ok?(quick = false)
  unsatisfied = Hash.new {|h,k| h[k] = [] }
  each do |spec|
    spec.runtime_dependencies.each do |dep|
      inst = Gem::Specification.any? do |installed_spec|
        dep.name == installed_spec.name &&
          dep.requirement.satisfied_by?(installed_spec.version)
      end

      unless inst || @specs.find {|s| s.satisfies_requirement? dep }
        unsatisfied[spec.name] << dep
        return unsatisfied if quick
      end
    end
  end

  unsatisfied
end