Add Type.default_value and use it everywhere for internal

For reduce instantiating `Type::Value`.

activerecord/lib/active_record/attribute.rb

@@ -187,7 +187,7 @@ def changed_in_place?
 
       class Null < Attribute # :nodoc:
         def initialize(name)
-          super(name, nil, Type::Value.new)
+          super(name, nil, Type.default_value)
         end
 
         def type_cast(*)

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -437,7 +437,7 @@ def get_oid_type(oid, fmod, column_name, sql_type = "") # :nodoc:
 
           type_map.fetch(oid, fmod, sql_type) {
             warn "unknown OID #{oid}: failed to recognize type of '#{column_name}'. It will be treated as String."
-            Type::Value.new.tap do |cast_type|
+            Type.default_value.tap do |cast_type|
               type_map.register_type(oid, cast_type)
             end
           }

activerecord/lib/active_record/model_schema.rb

@@ -268,7 +268,7 @@ def columns
 
       def attribute_types # :nodoc:
         load_schema
-        @attribute_types ||= Hash.new(Type::Value.new)
+        @attribute_types ||= Hash.new(Type.default_value)
       end
 
       def yaml_encoder # :nodoc:

activerecord/lib/active_record/relation/calculations.rb

@@ -312,7 +312,7 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
           key = group_columns.map { |aliaz, col_name|
             column = type_for(col_name) do
               calculated_data.column_types.fetch(aliaz) do
-                Type::Value.new
+                Type.default_value
               end
             end
             type_cast_calculated_value(row[aliaz], column)

activerecord/lib/active_record/relation/query_methods.rb

@@ -80,14 +80,14 @@ def bound_attributes
         limit_bind = Attribute.with_cast_value(
           "LIMIT".freeze,
           connection.sanitize_limit(limit_value),
-          Type::Value.new,
+          Type.default_value,
         )
       end
       if offset_value
         offset_bind = Attribute.with_cast_value(
           "OFFSET".freeze,
           offset_value.to_i,
-          Type::Value.new,
+          Type.default_value,
         )
       end
       connection.combine_bind_parameters(

activerecord/lib/active_record/result.rb

@@ -32,8 +32,6 @@ module ActiveRecord
   class Result
     include Enumerable
 
-    IDENTITY_TYPE = Type::Value.new # :nodoc:
-
     attr_reader :columns, :rows, :column_types
 
     def initialize(columns, rows, column_types = {})
@@ -105,7 +103,7 @@ def initialize_copy(other)
 
       def column_type(name, type_overrides = {})
         type_overrides.fetch(name) do
-          column_types.fetch(name, IDENTITY_TYPE)
+          column_types.fetch(name, Type.default_value)
         end
       end
 

activerecord/lib/active_record/table_metadata.rb

@@ -33,7 +33,7 @@ def type(column_name)
       if klass
         klass.type_for_attribute(column_name.to_s)
       else
-        Type::Value.new
+        Type.default_value
       end
     end
 

activerecord/lib/active_record/type.rb

@@ -37,6 +37,10 @@ def lookup(*args, adapter: current_adapter_name, **kwargs) # :nodoc:
         registry.lookup(*args, adapter: adapter, **kwargs)
       end
 
+      def default_value # :nodoc:
+        @default_value ||= Value.new
+      end
+
       private
 
       def current_adapter_name

activerecord/lib/active_record/type/type_map.rb

@@ -11,7 +11,7 @@ def initialize
       end
 
       def lookup(lookup_key, *args)
-        fetch(lookup_key, *args) { default_value }
+        fetch(lookup_key, *args) { Type.default_value }
       end
 
       def fetch(lookup_key, *args, &block)
@@ -55,10 +55,6 @@ def perform_fetch(lookup_key, *args)
             yield lookup_key, *args
           end
         end
-
-        def default_value
-          @default_value ||= ActiveModel::Type::Value.new
-        end
     end
   end
 end