supporting StringJoin in the JoinSQL visitor

lib/arel/visitors/dot.rb

@@ -98,6 +98,7 @@ module Arel
       alias :visit_Arel_SqlLiteral :visit_String
       alias :visit_Fixnum :visit_String
       alias :visit_Symbol :visit_String
+      alias :visit_Arel_Nodes_SqlLiteral :visit_String
 
       def visit_Hash o
         o.each_with_index do |pair, i|

lib/arel/visitors/join_sql.rb

@@ -13,6 +13,10 @@ module Arel
         o.froms.grep(Nodes::Join).map { |x| visit x }.join ', '
       end
 
+      def visit_Arel_Nodes_StringJoin o
+        visit o.right
+      end
+
       def visit_Arel_Nodes_OuterJoin o
         "OUTER JOIN #{visit o.right} #{visit o.constraint}"
       end

spec/arel/select_manager_spec.rb

@@ -223,6 +223,15 @@ module Arel
         }
         check manager.joins(manager).should == manager.join_sql
       end
+
+      it 'returns string join sql' do
+        table   = Table.new :users
+        aliaz   = table.alias
+        manager = Arel::SelectManager.new Table.engine
+        manager.from Nodes::StringJoin.new(table, 'hello')
+        manager.join_sql.should be_like %{ 'hello' }
+        check manager.joins(manager).should == manager.join_sql
+      end
     end
 
     describe 'order_clauses' do