bind parameters can be differentiated from sql literals

lib/arel/nodes/sql_literal.rb

@@ -6,5 +6,8 @@ module Arel
       include Arel::AliasPredication
       include Arel::OrderPredications
     end
+
+    class BindParam < SqlLiteral
+    end
   end
 end

lib/arel/visitors/depth_first.rb

@@ -109,6 +109,7 @@ module Arel
       alias :visit_Arel_Nodes_Lock               :terminal
       alias :visit_Arel_Nodes_Node               :terminal
       alias :visit_Arel_Nodes_SqlLiteral         :terminal
+      alias :visit_Arel_Nodes_BindParam          :terminal
       alias :visit_Arel_SqlLiteral               :terminal
       alias :visit_BigDecimal                    :terminal
       alias :visit_Bignum                        :terminal

lib/arel/visitors/dot.rb

@@ -65,6 +65,7 @@ module Arel
         visit_edge o, "expr"
       end
       alias :visit_Arel_Nodes_Group             :unary
+      alias :visit_Arel_Nodes_BindParam         :unary
       alias :visit_Arel_Nodes_Grouping          :unary
       alias :visit_Arel_Nodes_Having            :unary
       alias :visit_Arel_Nodes_Limit             :unary

lib/arel/visitors/to_sql.rb

@@ -374,6 +374,7 @@ key on UpdateManager using UpdateManager#key=
 
       def literal o; o end
 
+      alias :visit_Arel_Nodes_BindParam  :literal
       alias :visit_Arel_Nodes_SqlLiteral :literal
       alias :visit_Arel_SqlLiteral       :literal # This is deprecated
       alias :visit_Bignum                :literal

test/nodes/test_node.rb

@@ -11,6 +11,7 @@ module Arel
         Nodes.const_get(k)
       }.grep(Class).each do |klass|
         next if Nodes::SqlLiteral == klass
+        next if Nodes::BindParam == klass
         next if klass.name =~ /^Arel::Nodes::Test/
         assert klass.ancestors.include?(Nodes::Node), klass.name
       end

test/visitors/test_to_sql.rb

@@ -9,6 +9,12 @@ module Arel
         @attr = @table[:id]
       end
 
+      it 'works with BindParams' do
+        node = Nodes::BindParam.new 'omg'
+        sql = @visitor.accept node
+        sql.must_be_like 'omg'
+      end
+
       it 'can define a dispatch method' do
         visited = false
         viz = Class.new(Arel::Visitors::Visitor) {