A new release of datamapper is probably needed. dm-types depends on bcrypt-ruby ~> 2.1.4, whereas activemodel on which both actionpack and activerecord (and thus rails) depend, has a dependency on bcrypt-ruby ~> 3.0.0. This prevents dm from even bundling on Rails 3.1.
I would submit a pull request for fixing this dependency, but I can't get the datamapper tests to run, so it doesn't really feel worthwhile.
A new release of datamapper is probably needed. dm-types depends on bcrypt-ruby ~> 2.1.4, whereas activemodel on which both actionpack and activerecord (and thus rails) depend, has a dependency on bcrypt-ruby ~> 3.0.0. This prevents dm from even bundling on Rails 3.1.
I would submit a pull request for fixing this dependency, but I can't get the datamapper tests to run, so it doesn't really feel worthwhile.