Gem::SpecificationPolicy#validate_array_attribute

# File tmp/rubies/ruby-3.2.0/lib/rubygems/specification_policy.rb, line 332
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.kind_of?(klass) }
    error "#{field} must be an Array of #{klass}"
  end
end