MonkeyPatch for cancan#646

cancan_initializer.rb

require "cancan/model_adapters/active_record_adapter"

class CanCan::ModelAdapters::ActiveRecordAdapter

  def merge_conditions(sql, conditions_hash, behavior)
    conditions_hash = Squeel::Nodes::Literal.new(conditions_hash) if conditions_hash.is_a? String
    if conditions_hash.blank?
      Squeel::Nodes::Literal.new(behavior ? true_sql : false_sql)
    else
      case sql
      when true_sql
        behavior ? Squeel::Nodes::Literal.new(true_sql) : Squeel::Nodes::Not.new(conditions_hash)
      when false_sql
        behavior ? conditions_hash : Squeel::Nodes::Literal.new(false_sql)
      else
        sql = Squeel::Nodes::Literal.new(sql) if sql.is_a? String
        behavior ? Squeel::Nodes::Or.new(conditions_hash,sql) : Squeel::Nodes::And.new([Squeel::Nodes::Not.new(conditions_hash),sql])
      end
    end
  end
  
end