Gem::Uninstaller#uninstall

# File tmp/rubies/ruby-3.0.5/lib/rubygems/uninstaller.rb, line 82
def uninstall
  dependency = Gem::Dependency.new @gem, @version

  list = []

  dirs =
    Gem::Specification.dirs +
    [Gem.default_specifications_dir]

  Gem::Specification.each_spec dirs do |spec|
    next unless dependency.matches_spec? spec

    list << spec
  end

  if list.empty?
    raise Gem::InstallError, "gem #{@gem.inspect} is not installed"
  end

  default_specs, list = list.partition do |spec|
    spec.default_gem?
  end
  warn_cannot_uninstall_default_gems(default_specs - list)
  @default_specs_matching_uninstall_params = default_specs

  list, other_repo_specs = list.partition do |spec|
    @gem_home == spec.base_dir or
      (@user_install and spec.base_dir == Gem.user_dir)
  end

  list.sort!

  if list.empty?
    return unless other_repo_specs.any?

    other_repos = other_repo_specs.map {|spec| spec.base_dir }.uniq

    message = ["#{@gem} is not installed in GEM_HOME, try:"]
    message.concat other_repos.map {|repo|
      "\tgem uninstall -i #{repo} #{@gem}"
    }

    raise Gem::InstallError, message.join("\n")
  elsif @force_all
    remove_all list

  elsif list.size > 1
    gem_names = list.map {|gem| gem.full_name }
    gem_names << "All versions"

    say
    _, index = choose_from_list "Select gem to uninstall:", gem_names

    if index == list.size
      remove_all list
    elsif index >= 0 && index < list.size
      uninstall_gem list[index]
    else
      say "Error: must enter a number [1-#{list.size + 1}]"
    end
  else
    uninstall_gem list.first
  end
end