gistfile1.txt

source 'http://gemcutter.org'

group :ar2 do
  gem "activerecord", '~> 2.3'
end

group :ar3 do
  gem "activerecord", '~> 3'
end

# obviously can't work, raises:
No compatible versions could be found for required dependencies: (Bundler::VersionConflict)
    Conflict on: "activerecord":
    * activerecord (2.3.4) activated by activerecord (~> 2.3, runtime)
    * activerecord (~> 3, runtime) required in Gemfile