Gem::SpecificationPolicy#validate_array_attribute

# File tmp/rubies/ruby-4.0.0/lib/rubygems/specification_policy.rb, line 324
def validate_array_attribute(field)
  val = @specification.send(field)
  klass = case field
          when :dependencies then
            Gem::Dependency
          else
            String
  end

  unless Array === val && val.all? {|x| x.is_a?(klass) || (field == :licenses && x.nil?) }
    error "#{field} must be an Array of #{klass}"
  end
end