Gem::Version#approximate_recommendation

# File tmp/rubies/ruby-4.0.0/lib/rubygems/version.rb, line 327
def approximate_recommendation
  segments = self.segments

  segments.pop    while segments.any? {|s| String === s }
  segments.pop    while segments.size > 2
  segments.push 0 while segments.size < 2

  recommendation = "~> #{segments.join(".")}"
  recommendation += ".a" if prerelease?
  recommendation
end