class Gem::Specification

def validate_dependencies # :nodoc:
  # NOTE: see REFACTOR note in Gem::Dependency about types - this might be brittle
  seen = Gem::Dependency::TYPES.inject({}) { |types, type| types.merge({ type => {}}) }
  error_messages = []
  warning_messages = []
  dependencies.each do |dep|
    if prev = seen[dep.type][dep.name] then
      error_messages << <<-MESSAGE
plicate dependency on #{dep}, (#{prev.requirement}) use:
  add_#{dep.type}_dependency '#{dep.name}', '#{dep.requirement}', '#{prev.requirement}'
      MESSAGE
    end
    seen[dep.type][dep.name] = dep
    prerelease_dep = dep.requirements_list.any? do |req|
      Gem::Requirement.new(req).prerelease?
    end
    warning_messages << "prerelease dependency on #{dep} is not recommended" if
      prerelease_dep && !version.prerelease?
    overly_strict = dep.requirement.requirements.length == 1 &&
      dep.requirement.requirements.any? do |op, version|
        op == '~>' and
          not version.prerelease? and
          version.segments.length > 2 and
          version.segments.first != 0
      end
    if overly_strict then
      _, dep_version = dep.requirement.requirements.first
      base = dep_version.segments.first 2
      warning_messages << <<-WARNING
ssimistic dependency on #{dep} may be overly strict
if #{dep.name} is semantically versioned, use:
  add_#{dep.type}_dependency '#{dep.name}', '~> #{base.join '.'}', '>= #{dep_version}'
      WARNING
    end
    open_ended = dep.requirement.requirements.all? do |op, version|
      not version.prerelease? and (op == '>' or op == '>=')
    end
    if open_ended then
      op, dep_version = dep.requirement.requirements.first
      base = dep_version.segments.first 2
      bugfix = if op == '>' then
                 ", '> #{dep_version}'"
               elsif op == '>=' and base != dep_version.segments then
                 ", '>= #{dep_version}'"
               end
      warning_messages << <<-WARNING
en-ended dependency on #{dep} is not recommended
if #{dep.name} is semantically versioned, use:
  add_#{dep.type}_dependency '#{dep.name}', '~> #{base.join '.'}'#{bugfix}
      WARNING
    end
  end
  if error_messages.any?
    raise Gem::InvalidSpecificationException, error_messages.join
  end
  if warning_messages.any?
    warning_messages.each { |warning_message| warning warning_message }
  end
end