class Bundler::Installer

def check_rubygems_cache_dir
  require 'digest'
  cached_gems = Dir["#{Bundler.rubygems.gem_dir}/cache/*.gem"]
  same_size_gems = cached_gems.group_by { |f| File.size(f) }.
    values.select { |names| names.size > 1 }
  same_hash_gems = same_size_gems.flatten.group_by do |f|
    Digest::SHA1.hexdigest(File.read(f))
  end.values.select { |names| names.size > 1 }
  if same_hash_gems.any?
    Bundler.ui.warn "It looks like some of your gems are corrupted!"
    same_hash_gems.each { |name| Bundler.ui.warn "  * #{name}" }
    Bundler.ui.warn "Please report this issue to the Bundler issue tracker " \
      "on Github, and include the log file at .bundle/install.log. Thanks!"
  end
end