```ruby
require 'slim_migrations/version'

module SlimMigrations
  class Railtie < Rails::Railtie
    rake_tasks do
      load "tasks/slim_migrations_tasks.rake"
    end
  end
end

module Kernel
  private

  # initialize migrations with <tt>migration do</tt> instead of <tt>class SomeMigration < ActiveRecord::Migration</tt>
  def migration(&block)
    if caller[0].rindex(/(?:[0-9]+)_([_a-z0-9]*).rb:\d+(?::in `.*')?$/)
      m = Object.const_set $1.camelize, Class.new(ActiveRecord::Migration)
      m.class_eval(&block) # 3.1
    else
      raise ArgumentError, "Could not create migration at: #{caller[0]}"
    end
  end
end
```

Fix regex that creates migration class
user
```ruby
require 'slim_migrations/version'

module SlimMigrations
  class Railtie < Rails::Railtie
    rake_tasks do
      load "tasks/slim_migrations_tasks.rake"
    end
  end
end

module Kernel
  private

  # initialize migrations with <tt>migration do</tt> instead of <tt>class SomeMigration < ActiveRecord::Migration</tt>
  def migration(&block)
    if caller[0].rindex(/\/(?:[0-9]+)_([_a-z0-9]*).rb:\d+(?::in `.*')?$/)
      m = Object.const_set $1.camelize, Class.new(ActiveRecord::Migration)
      m.class_eval(&block) # 3.1
    else
      raise ArgumentError, "Could not create migration at: #{caller[0]}"
    end
  end
end
```
assistant