diff --git a/benchmarks/json/scripts/nitcc_parser.nit b/benchmarks/json/scripts/nitcc_parser.nit
index f09b746c71..627ae39550 100644
--- a/benchmarks/json/scripts/nitcc_parser.nit
+++ b/benchmarks/json/scripts/nitcc_parser.nit
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import json
+import json::static
 
 var text = args.first.to_path.read_all
 var json = text.parse_json
diff --git a/contrib/benitlux/src/client/base.nit b/contrib/benitlux/src/client/base.nit
index 7cfde7292a..28b4c889de 100644
--- a/contrib/benitlux/src/client/base.nit
+++ b/contrib/benitlux/src/client/base.nit
@@ -19,7 +19,7 @@ import app::ui
 import app::data_store
 import app::http_request
 import android::aware
-import json::serialization
+import json
 
 import benitlux_model
 import translations
diff --git a/contrib/benitlux/src/server/benitlux_controller.nit b/contrib/benitlux/src/server/benitlux_controller.nit
index 56493455b4..a2ab392d58 100644
--- a/contrib/benitlux/src/server/benitlux_controller.nit
+++ b/contrib/benitlux/src/server/benitlux_controller.nit
@@ -19,7 +19,7 @@ module benitlux_controller
 
 import nitcorn
 import nitcorn::restful
-private import json::serialization
+private import json
 
 import benitlux_model
 import benitlux_db
diff --git a/contrib/neo_doxygen/src/model/descriptions.nit b/contrib/neo_doxygen/src/model/descriptions.nit
index 1f504ef837..58ef0e6c99 100644
--- a/contrib/neo_doxygen/src/model/descriptions.nit
+++ b/contrib/neo_doxygen/src/model/descriptions.nit
@@ -16,6 +16,7 @@
 module model::descriptions
 
 import json::static
+import json
 
 # Documentation associated to an entity.
 #
@@ -106,8 +107,8 @@ class Documentation
 	# Is the documentation empty?
 	fun is_empty: Bool do return content.is_empty
 
-	redef fun to_json do return content.to_json
-	redef fun append_json(b) do content.append_json(b)
+	redef fun serialize_to(v) do content.serialize_to v
+	redef fun accept_json_serializer(v) do content.serialize_to v
 end
 
 # A `Jsonable` array of strings.
diff --git a/contrib/neo_doxygen/src/model/graph.nit b/contrib/neo_doxygen/src/model/graph.nit
index 74a81b5e6b..26c8e669a7 100644
--- a/contrib/neo_doxygen/src/model/graph.nit
+++ b/contrib/neo_doxygen/src/model/graph.nit
@@ -221,7 +221,7 @@ end
 abstract class Compound
 	super Entity
 
-	# Set the declared visibility (the proctection) of the compound.
+	# Set the declared visibility (the protection) of the compound.
 	fun visibility=(visibility: String) do
 		self["visibility"] = visibility
 	end
@@ -233,7 +233,7 @@ abstract class Compound
 
 	# Declare an inner namespace.
 	#
-	# Note: Althought Doxygen indicates that the name is optional,
+	# Note: Although Doxygen indicates that the name is optional,
 	# declarations with an empty name are not supported yet, except for the root
 	# namespace. For the root namespace, both arguments are empty.
 	#
@@ -246,7 +246,7 @@ abstract class Compound
 
 	# Declare an inner class.
 	#
-	# Note: Althought Doxygen indicates that both arguments are optional,
+	# Note: Although Doxygen indicates that both arguments are optional,
 	# declarations with an empty ID are not supported yet.
 	#
 	# Parameters:
@@ -292,7 +292,7 @@ class Namespace
 		self.labels.add("MGroup")
 	end
 
-	redef fun declare_namespace(id: String, full_name: String) do
+	redef fun declare_namespace(id, full_name) do
 		inner_namespaces.add new NamespaceRef(id, full_name)
 	end
 
diff --git a/contrib/neo_doxygen/src/model/location.nit b/contrib/neo_doxygen/src/model/location.nit
index b78a2ef875..d5f37278e0 100644
--- a/contrib/neo_doxygen/src/model/location.nit
+++ b/contrib/neo_doxygen/src/model/location.nit
@@ -16,6 +16,7 @@
 module location
 
 import json::static
+import json
 
 # A location inside a source file.
 class Location
@@ -36,11 +37,13 @@ class Location
 	# The one-based column index of the last character.
 	var column_end: Int = 1 is writable
 
-	redef fun to_s: String do
+	redef fun to_s do
+		var path = path
 		var file_part = "/dev/null:"
-		if path != null and path.length > 0 then file_part = "{path.as(not null)}:"
+		if path != null and path.length > 0 then file_part = "{path}:"
 		return "{file_part}{line_start},{column_start}--{line_end},{column_end}"
 	end
 
-	redef fun to_json do return to_s.to_json
+	redef fun serialize_to(v) do to_s.serialize_to v
+	redef fun accept_json_serializer(v) do to_s.serialize_to v
 end
diff --git a/contrib/neo_doxygen/src/tests/neo_doxygen_descriptions.nit b/contrib/neo_doxygen/src/tests/neo_doxygen_descriptions.nit
deleted file mode 100644
index d277be7dfa..0000000000
--- a/contrib/neo_doxygen/src/tests/neo_doxygen_descriptions.nit
+++ /dev/null
@@ -1,44 +0,0 @@
-# This file is part of NIT ( http://www.nitlanguage.org ).
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-# http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import model::descriptions
-
-# Copied from the documentation of `Documentation`.
-
-var doc = new Documentation
-
-doc.brief_description = "Do something."
-doc.detailed_description = ["Do not lunch a rocket."]
-assert doc.brief_description == "Do something."
-assert doc.detailed_description == ["Do not lunch a rocket."]
-assert doc.to_json == """["Do something.","Do not lunch a rocket."]"""
-
-doc.brief_description = ""
-doc.detailed_description = ["The answer is `42`."]
-assert doc.brief_description == "The answer is `42`."
-assert doc.detailed_description == ["The answer is `42`."]
-assert doc.to_json == """["The answer is `42`."]"""
-
-doc.detailed_description = ["The answer is `42`."]
-doc.brief_description = ""
-assert doc.brief_description == "The answer is `42`."
-assert doc.detailed_description == ["The answer is `42`."]
-assert doc.to_json == """["The answer is `42`."]"""
-
-doc.detailed_description = new Array[String]
-doc.brief_description = ""
-assert doc.is_empty
-assert doc.brief_description == ""
-assert doc.detailed_description == new Array[String]
-assert doc.to_json == "[]"
diff --git a/contrib/neo_doxygen/src/tests/neo_doxygen_member_resolve_introducer.nit b/contrib/neo_doxygen/src/tests/neo_doxygen_member_resolve_introducer.nit
deleted file mode 100644
index 4909e9de5a..0000000000
--- a/contrib/neo_doxygen/src/tests/neo_doxygen_member_resolve_introducer.nit
+++ /dev/null
@@ -1,34 +0,0 @@
-# This file is part of NIT ( http://www.nitlanguage.org ).
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-# http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import model::member
-
-# Copied from the documentation of `Member::resolve_introducer`.
-
-var g = new ProjectGraph("foo")
-var m1 = new Attribute(g)
-var m2 = new Attribute(g)
-var m3 = new Attribute(g)
-
-m1.model_id = "1"
-m1.put_in_graph
-m2.reimplement("1")
-m2.put_in_graph
-assert m1.resolve_introducer == m1.introducer
-assert m2.resolve_introducer == m1.introducer
-
-m3.model_id = "3"
-m3.reimplement("3")
-m3.put_in_graph
-assert m3.resolve_introducer == null
diff --git a/contrib/nitrpg/src/achievements.nit b/contrib/nitrpg/src/achievements.nit
index 9055b22876..2097ec363b 100644
--- a/contrib/nitrpg/src/achievements.nit
+++ b/contrib/nitrpg/src/achievements.nit
@@ -120,7 +120,7 @@ class Achievement
 			json["reward"].as(Int))
 	end
 
-	redef fun to_json do
+	redef fun to_json_object do
 		var json = super
 		json["id"] = id
 		json["name"] = name
diff --git a/contrib/nitrpg/src/events.nit b/contrib/nitrpg/src/events.nit
index c540dc5e91..08d387d540 100644
--- a/contrib/nitrpg/src/events.nit
+++ b/contrib/nitrpg/src/events.nit
@@ -104,7 +104,7 @@ class GameEvent
 		time = new ISODate.from_string(json["time"].as(String))
 	end
 
-	redef fun to_json do
+	redef fun to_json_object do
 		var json = new JsonObject
 		json["internal_id"] = internal_id.to_s
 		json["kind"] = kind
diff --git a/contrib/nitrpg/src/game.nit b/contrib/nitrpg/src/game.nit
index 504c445881..b1d8916f26 100644
--- a/contrib/nitrpg/src/game.nit
+++ b/contrib/nitrpg/src/game.nit
@@ -42,10 +42,10 @@ interface GameEntity
 	fun key: String is abstract
 
 	# Saves `self` in db.
-	fun save do game.db.collection(collection_name).save(to_json)
+	fun save do game.db.collection(collection_name).save(to_json_object)
 
 	# Json representation of `self`.
-	fun to_json: JsonObject do
+	fun to_json_object: JsonObject do
 		var json = new JsonObject
 		json["_id"] = key
 		return json
@@ -102,7 +102,7 @@ class Game
 	# Used to load entities from saved data.
 	fun from_json(json: JsonObject) do end
 
-	redef fun to_json do
+	redef fun to_json_object do
 		var json = super
 		json["name"] = name
 		return json
@@ -166,7 +166,7 @@ class Game
 	end
 
 	# Erase all saved data for this game.
-	fun clear do db.collection(collection_name).remove(to_json)
+	fun clear do db.collection(collection_name).remove(to_json_object)
 
 	# Verbosity level used fo stdout.
 	#
@@ -236,7 +236,7 @@ class Player
 		nitcoins = json["nitcoins"].as(Int)
 	end
 
-	redef fun to_json do
+	redef fun to_json_object do
 		var json = super
 		json["game"] = game.key
 		json["name"] = name
diff --git a/contrib/nitrpg/src/statistics.nit b/contrib/nitrpg/src/statistics.nit
index cde68161b5..764616f462 100644
--- a/contrib/nitrpg/src/statistics.nit
+++ b/contrib/nitrpg/src/statistics.nit
@@ -172,7 +172,7 @@ class GameStats
 		for k, v in values do self[k] = v.as(Int)
 	end
 
-	redef fun to_json do
+	redef fun to_json_object do
 		var obj = super
 		obj["period"] = period
 		obj["owner"] = owner.key
diff --git a/contrib/nitrpg/src/test_achievements.nit b/contrib/nitrpg/src/test_achievements.nit
index 033832f4a4..c210c6030d 100644
--- a/contrib/nitrpg/src/test_achievements.nit
+++ b/contrib/nitrpg/src/test_achievements.nit
@@ -51,7 +51,7 @@ class TestGame
 		var a3 = new Achievement(game, "test_id3", "test_name", "test_desc", 15)
 		game.add_achievement(a1)
 		game.add_achievement(a2)
-		game.db.collection("achievements").insert(a3.to_json)
+		game.db.collection("achievements").insert(a3.to_json_object)
 		var ok = [a1.id, a2.id]
 		var res = game.load_achievements
 		assert res.length == 2
diff --git a/contrib/nitrpg/src/test_events.nit b/contrib/nitrpg/src/test_events.nit
index b9605016db..640e8dc839 100644
--- a/contrib/nitrpg/src/test_events.nit
+++ b/contrib/nitrpg/src/test_events.nit
@@ -51,7 +51,7 @@ class TestGame
 		var event3 = new GameEvent(game, "test_kind", new JsonObject)
 		game.add_event(event1)
 		game.add_event(event2)
-		game.db.collection("events").insert(event3.to_json)
+		game.db.collection("events").insert(event3.to_json_object)
 		var ok = [event1.internal_id, event2.internal_id]
 		var res = game.load_events
 		assert res.length == 2
@@ -115,7 +115,7 @@ class TestGameEvent
 		var db = gen_test_db
 		var game = load_game("Morriar/nit", db)
 		var event = new GameEvent(game, "test_kind", new JsonObject)
-		assert event.to_json["kind"] == "test_kind"
+		assert event.to_json_object["kind"] == "test_kind"
 	end
 
 	fun test_init_from_json do
diff --git a/contrib/nitrpg/src/test_game.nit b/contrib/nitrpg/src/test_game.nit
index fceafb9ddd..25ddcadaa6 100644
--- a/contrib/nitrpg/src/test_game.nit
+++ b/contrib/nitrpg/src/test_game.nit
@@ -43,8 +43,8 @@ class TestGame
 
 		var player1 = new Player(game, "Morriar")
 		var player2 = new Player(ogame, "privat")
-		game.db.collection("players").insert(player1.to_json)
-		ogame.db.collection("players").insert(player2.to_json)
+		game.db.collection("players").insert(player1.to_json_object)
+		ogame.db.collection("players").insert(player2.to_json_object)
 
 		assert game.load_player("privat") == null
 		assert game.load_player("Morriar").name == "Morriar"
@@ -60,9 +60,9 @@ class TestGame
 		var player1 = new Player(game, "Morriar")
 		var player2 = new Player(ogame, "privat")
 		var player3 = new Player(game, "xymus")
-		game.db.collection("players").insert(player1.to_json)
-		ogame.db.collection("players").insert(player2.to_json)
-		game.db.collection("players").insert(player3.to_json)
+		game.db.collection("players").insert(player1.to_json_object)
+		ogame.db.collection("players").insert(player2.to_json_object)
+		game.db.collection("players").insert(player3.to_json_object)
 
 		var players = game.load_players
 		var ok = ["Morriar", "xymus"]
diff --git a/contrib/refund/src/refund_json.nit b/contrib/refund/src/refund_json.nit
index 4da71f584d..f670f9d90c 100644
--- a/contrib/refund/src/refund_json.nit
+++ b/contrib/refund/src/refund_json.nit
@@ -19,6 +19,7 @@ module refund_json
 
 import refund_base
 import json::static
+import json
 
 redef class RefundProcessor
 
@@ -89,6 +90,7 @@ redef class RefundProcessor
 	fun write_output(str: String, file: String) do
 		var ofs = new FileWriter.open(file)
 		ofs.write(str)
+		ofs.write("\n")
 		ofs.close
 	end
 
@@ -118,7 +120,7 @@ redef class RefundProcessor
 		exit 1
 	end
 
-	redef fun show_stats do print load_stats.to_json.to_pretty_json
+	redef fun show_stats do print load_stats.to_json_object.to_pretty_json
 
 	redef fun load_stats do
 		# If no stats found, return a new object
@@ -134,7 +136,7 @@ redef class RefundProcessor
 	end
 
 	redef fun save_stats(stats) do
-		write_output(stats.to_json.to_pretty_json, stats_file)
+		write_output(stats.to_json_object.to_pretty_json, stats_file)
 	end
 end
 
@@ -146,7 +148,7 @@ redef class RefundStats
 	end
 
 	# Outputs `self` as a JSON string.
-	fun to_json: JsonObject do
+	fun to_json_object: JsonObject do
 		var obj = new JsonObject
 		for k, v in self do obj[k] = v
 		return obj
diff --git a/contrib/refund/tests/res/json_error1.res b/contrib/refund/tests/res/json_error1.res
index 958aa8db6c..e7eb308d82 100644
--- a/contrib/refund/tests/res/json_error1.res
+++ b/contrib/refund/tests/res/json_error1.res
@@ -1,3 +1,3 @@
 {
-	"message": "Wrong input file (Unexpected Eof; is acceptable instead: value)"
+	"message": "Wrong input file (Empty JSON)"
 }
diff --git a/contrib/refund/tests/res/json_error3.res b/contrib/refund/tests/res/json_error3.res
index d35b98219a..83de0af287 100644
--- a/contrib/refund/tests/res/json_error3.res
+++ b/contrib/refund/tests/res/json_error3.res
@@ -1,3 +1,3 @@
 {
-	"message": "Wrong input file (Unexpected Eof; is acceptable instead: members, pair)"
+	"message": "Wrong input file (Malformed JSON object)"
 }
diff --git a/contrib/shibuqam/examples/shibuqamoauth.nit b/contrib/shibuqam/examples/shibuqamoauth.nit
index 2a52be90d1..bda76a3560 100644
--- a/contrib/shibuqam/examples/shibuqamoauth.nit
+++ b/contrib/shibuqam/examples/shibuqamoauth.nit
@@ -172,7 +172,7 @@ module shibuqamoauth
 
 import popcorn
 import shibuqam
-import json::serialization
+import json
 
 redef class HttpRequest
 	# percent decoded get or post parameter.
@@ -304,7 +304,6 @@ end
 
 redef class User
 	super Jsonable
-	redef fun to_json do return serialize_to_json(plain=true)
 end
 
 # Information about an authenticated used stored on the server to be given to the client.
diff --git a/contrib/tinks/src/client/linux_client.nit b/contrib/tinks/src/client/linux_client.nit
index bd60702d27..5e7cca4253 100644
--- a/contrib/tinks/src/client/linux_client.nit
+++ b/contrib/tinks/src/client/linux_client.nit
@@ -17,7 +17,7 @@ module linux_client
 
 import mnit::linux
 import linux::audio
-import json::serialization
+import json
 
 import client
 
diff --git a/contrib/tnitter/src/action.nit b/contrib/tnitter/src/action.nit
index 60ee384db9..f567294224 100644
--- a/contrib/tnitter/src/action.nit
+++ b/contrib/tnitter/src/action.nit
@@ -18,7 +18,7 @@
 module action
 
 import nitcorn
-import json::serialization
+import json
 
 import model
 import database
diff --git a/contrib/tnitter/src/push.nit b/contrib/tnitter/src/push.nit
index bc47789270..9900cfa227 100644
--- a/contrib/tnitter/src/push.nit
+++ b/contrib/tnitter/src/push.nit
@@ -16,7 +16,7 @@
 module push
 
 import nitcorn
-import json::serialization
+import json
 
 import model
 import database
diff --git a/contrib/tnitter/src/tnitter_app.nit b/contrib/tnitter/src/tnitter_app.nit
index cf1d162cd3..82180043bc 100644
--- a/contrib/tnitter/src/tnitter_app.nit
+++ b/contrib/tnitter/src/tnitter_app.nit
@@ -31,7 +31,7 @@ import app::ui
 import app::http_request
 import app::data_store
 import android::aware
-import json::serialization
+import json
 
 import model
 
diff --git a/examples/rosettacode/json_output.nit b/examples/rosettacode/json_output.nit
index 59fb72b1e6..800a310566 100644
--- a/examples/rosettacode/json_output.nit
+++ b/examples/rosettacode/json_output.nit
@@ -7,6 +7,7 @@
 # SEE: <http://rosettacode.org/wiki/JSON>
 module json_output
 
+import json::static
 import json
 
 var str = """{
diff --git a/lib/android/bundle/bundle.nit b/lib/android/bundle/bundle.nit
index 82acbec2b4..e02702a9a0 100644
--- a/lib/android/bundle/bundle.nit
+++ b/lib/android/bundle/bundle.nit
@@ -19,7 +19,7 @@
 module bundle
 
 import serialization
-import json::serialization
+import json
 
 import platform
 import activities
diff --git a/lib/android/intent/intent_api10.nit b/lib/android/intent/intent_api10.nit
index 746c0c4556..f9e6c3bf8e 100644
--- a/lib/android/intent/intent_api10.nit
+++ b/lib/android/intent/intent_api10.nit
@@ -21,7 +21,7 @@ module intent_api10
 import dalvik
 import android::bundle
 import serialization
-private import json::serialization
+private import json
 
 in "Java" `{
 	import android.content.Intent;
diff --git a/lib/android/shared_preferences/shared_preferences_api10.nit b/lib/android/shared_preferences/shared_preferences_api10.nit
index b2680875ed..f17661f90c 100644
--- a/lib/android/shared_preferences/shared_preferences_api10.nit
+++ b/lib/android/shared_preferences/shared_preferences_api10.nit
@@ -19,7 +19,7 @@ module shared_preferences_api10
 
 import dalvik
 import serialization
-private import json::serialization
+private import json
 
 in "Java" `{
 	import android.content.SharedPreferences;
diff --git a/lib/app/http_request.nit b/lib/app/http_request.nit
index 3fc48c67b9..0260cab243 100644
--- a/lib/app/http_request.nit
+++ b/lib/app/http_request.nit
@@ -17,7 +17,7 @@ module http_request
 
 import app_base
 import pthreads
-import json::serialization
+import json
 
 import linux::http_request is conditional(linux)
 import android::http_request is conditional(android)
diff --git a/lib/github/api.nit b/lib/github/api.nit
index 7c85422a40..8bd1ee3131 100644
--- a/lib/github/api.nit
+++ b/lib/github/api.nit
@@ -20,7 +20,7 @@
 module api
 
 import github_curl
-intrude import json::serialization
+intrude import json::serialization_read
 
 # Client to Github API
 #
@@ -512,8 +512,6 @@ abstract class GithubEntity
 
 	# Github page url.
 	var html_url: nullable String is writable
-
-	redef fun to_json do return serialize_to_json
 end
 
 # A Github user
@@ -1062,8 +1060,6 @@ end
 redef class ISODate
 	super Jsonable
 	serialize
-
-	redef fun to_json do return serialize_to_json
 end
 
 # JsonDeserializer specific for Github objects.
diff --git a/lib/github/events.nit b/lib/github/events.nit
index 2dc0af7537..3417de2ccc 100644
--- a/lib/github/events.nit
+++ b/lib/github/events.nit
@@ -18,7 +18,7 @@
 module events
 
 import api
-intrude import json::serialization
+intrude import json
 
 # Github event stub.
 class GithubEvent
@@ -33,8 +33,6 @@ class GithubEvent
 
 	# Repo where this event occured.
 	var repo: Repo is writable
-
-	redef fun to_json do return serialize_to_json
 end
 
 # Triggered when a commit comment is created.
diff --git a/lib/github/github_curl.nit b/lib/github/github_curl.nit
index b5874f3832..f2d5737371 100644
--- a/lib/github/github_curl.nit
+++ b/lib/github/github_curl.nit
@@ -18,6 +18,7 @@ module github_curl
 
 import curl
 import json::static
+import json
 
 # Specific Curl that know hot to talk to the github API
 class GithubCurl
@@ -127,9 +128,7 @@ class GithubError
 		json["message"] = message.to_json
 	end
 
-	redef fun to_json do
-		return json.to_json
-	end
+	redef fun serialize_to(v) do json.serialize_to v
 
 	redef fun to_s do return "[{name}] {super}"
 end
diff --git a/lib/ios/data_store.nit b/lib/ios/data_store.nit
index 6d1579d11f..a06586c6e6 100644
--- a/lib/ios/data_store.nit
+++ b/lib/ios/data_store.nit
@@ -17,7 +17,7 @@ module data_store
 
 import app::data_store
 import cocoa::foundation
-private import json::serialization
+private import json
 
 redef class App
 	redef var data_store = new UserDefaultView
diff --git a/lib/json/README.md b/lib/json/README.md
new file mode 100644
index 0000000000..b964d1cd66
--- /dev/null
+++ b/lib/json/README.md
@@ -0,0 +1,239 @@
+read and write JSON formatted text
+
+These services can be useful to communicate with a remote server or client,
+save data locally or even debug and understand the structure of a Nit object.
+There is a single API to write JSON, and three API to read depending on the use case.
+
+# Write JSON
+
+Writing Nit objects to JSON format can be useful to communicate with a remote service,
+save data locally or even debug and understand the structure of an object.
+There is two related services to write JSON object, the method
+`serialize_to_json` and the object `JsonSerializer`.
+The method `serialize_to_json` is actually a shortcut to `JsonSerializer`, both
+share the same features.
+
+## Write plain JSON
+
+Passing the argument `plain=true` to `serialize_to_json` generates plain and clean JSON.
+This format is non-Nit program, it cannot be fully deserialized back to Nit objects.
+The argument `pretty=true` generates JSON for humans, with more spaces and line breaks.
+
+The Nit objects to write must subclass `Serializable` and implement its services.
+Most classes from the `core` library are already supported, including collections, numeric values, etc.
+For your local objects, you can annotate them with `serialize` to automate subclassing
+`Serializable` and the implementation of its services.
+
+### Example
+
+~~~
+class Person
+    serialize
+
+    var name: String
+    var year_of_birth: Int
+    var next_of_kin: nullable Person
+end
+
+var bob = new Person("Bob", 1986)
+assert bob.serialize_to_json(pretty=true, plain=true) == """
+{
+	"name": "Bob",
+	"year_of_birth": 1986,
+	"next_of_kin": null
+}"""
+
+var alice = new Person("Alice", 1978, bob)
+assert alice.serialize_to_json(pretty=true, plain=true) == """
+{
+	"name": "Alice",
+	"year_of_birth": 1978,
+	"next_of_kin": {
+		"name": "Bob",
+		"year_of_birth": 1986,
+		"next_of_kin": null
+	}
+}"""
+
+# You can also build JSON objects as a `Map`
+var charlie = new Map[String, nullable Serializable]
+charlie["name"] = "Charlie"
+charlie["year_of_birth"] = 1968
+charlie["next_of_kin"] = alice
+assert charlie.serialize_to_json(pretty=true, plain=true) == """
+{
+	"name": "Charlie",
+	"year_of_birth": 1968,
+	"next_of_kin": {
+		"name": "Alice",
+		"year_of_birth": 1978,
+		"next_of_kin": {
+			"name": "Bob",
+			"year_of_birth": 1986,
+			"next_of_kin": null
+		}
+	}
+}"""
+~~~
+
+## Write JSON with metadata
+
+By default, `serialize_to_json` and `JsonSerializer` include metadate in the generated JSON.
+This metadata is used by `JsonDeserializer` when reading the JSON code to recreate
+the Nit object with the exact original type.
+The metadata allows to avoid repeating an object and its resolves cycles in the serialized objects.
+
+For more information on Nit serialization, see: ../serialization/README.md
+
+
+# Read JSON
+
+There are a total of 3 API to read JSON:
+* `JsonDeserializer` reads JSON to recreate complex Nit objects (discussed here),
+* the module `json::dynamic` provides an easy API to explore JSON objects,
+* the module `json::static` offers a low-level service to parse JSON and create basic Nit objects.
+
+The class `JsonDeserializer` reads JSON code to recreate objects.
+It can use the metadata in the JSON code, to recreate precise Nit objects.
+Otherwise, JSON objects are recreated to simple Nit types: `Map`, `Array`, etc.
+Errors are reported to the attribute `JsonDeserializer::errors`.
+
+The type to recreate is either declared or inferred:
+
+1. The JSON object defines a `__class` key with the name of the Nit class as value.
+   This attribute is generated by the `JsonSerializer` with other metadata,
+   it can also be specified by other external tools.
+2. A refinement of `JsonDeserializer::class_name_heuristic` identifies the Nit class.
+3. If all else fails, `JsonDeserializer` uses the static type of the attribute,
+   or the type name passed to `deserialize`.
+
+The method `from_json_string` is a shortcut to `JsonDeserializer` which prints
+errors to the console. It is fit only for small scripts and other quick and dirty usage.
+
+### Example
+
+~~~
+class Triangle
+    serialize
+
+    var corners = new Array[Point]
+    redef var to_s is serialize_as("name")
+end
+
+class Point
+    serialize
+
+    var x: Int
+    var y: Int
+end
+
+# Metadata on each JSON object tells the deserializer what is its Nit type,
+# and it supports special types such as generic collections.
+var json_with_metadata = """{
+    "__class": "Triangle",
+    "corners": {"__class": "Array[Point]",
+                "__items": [{"__class": "Point", "x": 0, "y": 0},
+                            {"__class": "Point", "x": 3, "y": 0},
+                            {"__class": "Point", "x": 2, "y": 2}]},
+    "name": "some triangle"
+}"""
+
+var deserializer = new JsonDeserializer(json_with_metadata)
+var object = deserializer.deserialize
+assert deserializer.errors.is_empty
+assert object != null
+
+# However most non-Nit services won't add the metadata and instead produce plain JSON.
+# Without a "__class", the deserializer relies on `class_name_heuristic` and the static type.
+# The type of the root object to deserialize can be specified by an argument passed to `deserialize`.
+var plain_json = """{
+    "corners": [{"x": 0, "y": 0},
+                {"x": 3, "y": 0},
+                {"x": 2, "y": 2}],
+    "name": "the same triangle"
+}"""
+
+deserializer = new JsonDeserializer(plain_json)
+object = deserializer.deserialize("Triangle")
+assert deserializer.errors.is_empty # If false, `object` is invalid
+~~~
+
+### Missing attributes and default values
+
+When reading JSON, some attributes expected by Nit classes may be missing.
+The JSON object may come from an external API using optional attributes or
+from a previous version of your program without the attributes.
+When an attribute is not found, the deserialization engine acts in one of three ways:
+
+1. If the attribute has a default value or if it is annotated by `lazy`,
+   the engine leave the attribute to the default value. No error is raised.
+2. If the static type of the attribute is nullable, the engine sets
+   the attribute to `null`. No error is raised.
+3. Otherwise, the engine raises an error and does not set the attribute.
+   The caller must check for `errors` and must not read from the attribute.
+
+~~~
+class MyConfig
+    serialize
+
+    var width: Int # Must be in JSON or an error is raised
+    var height = 4
+    var volume_level = 8 is lazy
+    var player_name: nullable String
+    var tmp_dir: nullable String = "/tmp" is lazy
+end
+
+# ---
+# JSON object with all expected attributes -> OK
+var plain_json = """
+{
+    "width": 11,
+    "height": 22,
+    "volume_level": 33,
+    "player_name": "Alice",
+    "tmp_dir": null
+}"""
+var deserializer = new JsonDeserializer(plain_json)
+var obj = deserializer.deserialize("MyConfig")
+
+assert deserializer.errors.is_empty
+assert obj isa MyConfig
+assert obj.width == 11
+assert obj.height == 22
+assert obj.volume_level == 33
+assert obj.player_name == "Alice"
+assert obj.tmp_dir == null
+
+# ---
+# JSON object missing optional attributes -> OK
+plain_json = """
+{
+    "width": 11
+}"""
+deserializer = new JsonDeserializer(plain_json)
+obj = deserializer.deserialize("MyConfig")
+
+assert deserializer.errors.is_empty
+assert obj isa MyConfig
+assert obj.width == 11
+assert obj.height == 4
+assert obj.volume_level == 8
+assert obj.player_name == null
+assert obj.tmp_dir == "/tmp"
+
+# ---
+# JSON object missing the mandatory attribute -> Error
+plain_json = """
+{
+    "player_name": "Bob",
+}"""
+deserializer = new JsonDeserializer(plain_json)
+obj = deserializer.deserialize("MyConfig")
+
+# There's an error, `obj` is partial
+assert deserializer.errors.length == 1
+
+# Still, we can access valid attributes
+assert obj isa MyConfig
+assert obj.player_name == "Bob"
+~~~
diff --git a/lib/json/error.nit b/lib/json/error.nit
index 85e6154401..26a9952033 100644
--- a/lib/json/error.nit
+++ b/lib/json/error.nit
@@ -16,6 +16,7 @@ import nitcc_runtime
 # Ill-formed JSON.
 class JsonParseError
 	super Error
+	serialize
 
 	# The location of the error in the original text.
 	var position: nullable Position
diff --git a/lib/json/json.nit b/lib/json/json.nit
index 7df7e82448..391f746ae9 100644
--- a/lib/json/json.nit
+++ b/lib/json/json.nit
@@ -1,8 +1,5 @@
 # This file is part of NIT ( http://www.nitlanguage.org ).
 #
-# Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
-# Copyright 2014 Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
-#
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -15,20 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Libraries to manipulate JSON strings.
-#
-# Both `dynamic` and `static` modules provide at least a method to parse a
-# value written in JSON, but only `static` provide a method to translate a
-# value into JSON.
-#
-# The `dynamic` module provides a simple interface to get information
-# from a JSON document. You must be careful as all services are provided on
-# each nodes and a wrongful use can `abort`.
-#
-# The `static` module provides a common interface for anything that can be
-# translated into a JSON document. The provided parsing method return a
-# nullable Nit object that must then be type-checked before it can be used.
+# Read and write JSON formatted text using the standard serialization services
 module json
 
-import static
-import dynamic
+import serialization_write
+import serialization_read
diff --git a/lib/json/serialization.nit b/lib/json/serialization.nit
deleted file mode 100644
index 983f50b7c3..0000000000
--- a/lib/json/serialization.nit
+++ /dev/null
@@ -1,968 +0,0 @@
-# This file is part of NIT ( http://www.nitlanguage.org ).
-#
-# Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Handles serialization and deserialization of objects to/from JSON
-#
-# ## Writing JSON with metadata
-#
-# `JsonSerializer` write Nit objects that subclass `Serializable` to JSON,
-# and `JsonDeserializer` can read them. They both use metadata added to the
-# generated JSON to recreate the Nit instances with the exact original type.
-#
-# For more information on Nit serialization, see: ../serialization/README.md
-#
-# ## Writing plain JSON
-#
-# The attribute `JsonSerializer::plain_json` triggers generating plain and
-# clean JSON. This format is easier to read for an human and a non-Nit program,
-# but it cannot be fully deserialized. It can still be read by services from
-# `json::static` and `json::dynamic`.
-#
-# A shortcut to these writing services is provided by `Serializable::serialize_to_json`.
-#
-# ### Usage Example
-#
-# ~~~nitish
-# import json::serialization
-#
-# class Person
-#     serialize
-#
-#     var name: String
-#     var year_of_birth: Int
-#     var next_of_kin: nullable Person
-# end
-#
-# var bob = new Person("Bob", 1986)
-# var alice = new Person("Alice", 1978, bob)
-#
-# assert bob.serialize_to_json(pretty=true, plain=true) == """
-#{
-#	"name": "Bob",
-#	"year_of_birth": 1986,
-#	"next_of_kin": null
-#}"""
-#
-# assert alice.serialize_to_json(pretty=true, plain=true) == """
-#{
-#	"name": "Alice",
-#	"year_of_birth": 1978,
-#	"next_of_kin": {
-#		"name": "Bob",
-#		"year_of_birth": 1986,
-#		"next_of_kin": null
-#	}
-#}"""
-# ~~~
-#
-# ## Read JSON to create Nit objects
-#
-# The `JsonDeserializer` supports reading JSON code with or without metadata.
-# It can create Nit objects from a remote service returning JSON data
-# or to read local configuration files as Nit objects.
-# However, it needs to know which Nit class to recreate from each JSON object.
-# The class is either declared or inferred:
-#
-# 1. The JSON object defines a `__class` key with the name of the Nit class as value.
-#    This attribute is generated by the `JsonSerializer` with other metadata,
-#    it can also be specified by other external tools.
-# 2. A refinement of `JsonDeserializer::class_name_heuristic` identifies the Nit class.
-# 3. If all else fails, `JsonDeserializer` uses the static type of the attribute.
-#
-# ### Usage Example
-#
-# ~~~nitish
-# import json::serialization
-#
-# class Triangle
-#     serialize
-#
-#     var corners = new Array[Point]
-#     redef var to_s is serialize_as("name")
-# end
-#
-# class Point
-#     serialize
-#
-#     var x: Int
-#     var y: Int
-# end
-#
-# # Metadata on each JSON object tells the deserializer what is its Nit type,
-# # and it supports special types such as generic collections.
-# var json_with_metadata = """{
-#     "__class": "Triangle",
-#     "corners": {"__class": "Array[Point]",
-#                 "__items": [{"__class": "Point", "x": 0, "y": 0},
-#                             {"__class": "Point", "x": 3, "y": 0},
-#                             {"__class": "Point", "x": 2, "y": 2}]},
-#     "name": "some triangle"
-# }"""
-#
-# var deserializer = new JsonDeserializer(json_with_metadata)
-# var object = deserializer.deserialize
-# assert deserializer.errors.is_empty
-# assert object != null
-# print object
-#
-# # However most non-Nit services won't add the metadata and instead produce plain JSON.
-# # Without a "__class", the deserializer relies on `class_name_heuristic` and the static type.
-# # The type of the root object to deserialize can be specified by calling
-# # its deserialization constructor `from_deserializer`.
-# var plain_json = """{
-#     "corners": [{"x": 0, "y": 0},
-#                 {"x": 3, "y": 0},
-#                 {"x": 2, "y": 2}],
-#     "name": "the same triangle"
-# }"""
-#
-# deserializer = new JsonDeserializer(plain_json)
-# object = new Triangle.from_deserializer(deserializer)
-# assert deserializer.errors.is_empty # If false, `obj` is invalid
-# print object
-# ~~~
-#
-# ### Missing attributes and default values
-#
-# When reading JSON, some attributes expected by Nit classes may be missing.
-# The JSON object may come from an external API using optional attributes or
-# from a previous version of your program without the attributes.
-# When an attribute is not found, the deserialization engine acts in one of three ways:
-#
-# 1. If the attribute has a default value or if it is annotated by `lazy`,
-#    the engine leave the attribute to the default value. No error is raised.
-# 2. If the static type of the attribute is nullable, the engine sets
-#    the attribute to `null`. No error is raised.
-# 3. Otherwise, the engine raises an error and does not set the attribute.
-#    The caller must check for `errors` and must not read from the attribute.
-#
-# ~~~nitish
-# import json::serialization
-#
-# class MyConfig
-#     serialize
-#
-#     var width: Int # Must be in JSON or an error is raised
-#     var height = 4
-#     var volume_level = 8 is lazy
-#     var player_name: nullable String
-#     var tmp_dir: nullable String = "/tmp" is lazy
-# end
-#
-# # ---
-# # JSON object with all expected attributes -> OK
-# var plain_json = """
-# {
-#     "width": 11,
-#     "height": 22,
-#     "volume_level": 33,
-#     "player_name": "Alice",
-#     "tmp_dir": null
-# }"""
-# var deserializer = new JsonDeserializer(plain_json)
-# var obj = new MyConfig.from_deserializer(deserializer)
-#
-# assert deserializer.errors.is_empty
-# assert obj.width == 11
-# assert obj.height == 22
-# assert obj.volume_level == 33
-# assert obj.player_name == "Alice"
-# assert obj.tmp_dir == null
-#
-# # ---
-# # JSON object missing optional attributes -> OK
-# plain_json = """
-# {
-#     "width": 11
-# }"""
-# deserializer = new JsonDeserializer(plain_json)
-# obj = new MyConfig.from_deserializer(deserializer)
-#
-# assert deserializer.errors.is_empty
-# assert obj.width == 11
-# assert obj.height == 4
-# assert obj.volume_level == 8
-# assert obj.player_name == null
-# assert obj.tmp_dir == "/tmp"
-#
-# # ---
-# # JSON object missing the mandatory attribute -> Error
-# plain_json = """
-# {
-#     "player_name": "Bob",
-# }"""
-# deserializer = new JsonDeserializer(plain_json)
-# obj = new MyConfig.from_deserializer(deserializer)
-#
-# # There's an error, `obj` is partial
-# assert deserializer.errors.length == 1
-#
-# # Still, we can access valid attributes
-# assert obj.player_name == "Bob"
-# ~~~
-module serialization
-
-import ::serialization::caching
-private import ::serialization::engine_tools
-private import static
-private import string_parser
-
-# Serializer of Nit objects to Json string.
-class JsonSerializer
-	super CachingSerializer
-
-	# Target writing stream
-	var stream: Writer
-
-	# Write plain JSON? Standard JSON without metadata for deserialization
-	#
-	# If `false`, the default, serialize to support deserialization:
-	#
-	# * Write metadata, including the types of the serialized objects so they can
-	#   be deserialized to their original form using `JsonDeserializer`.
-	# * Use references when an object has already been serialized so to not duplicate it.
-	# * Support cycles in references.
-	# * Preserve the Nit `Char` type as an object because it does not exist in JSON.
-	# * The generated JSON is standard and can be read by non-Nit programs.
-	#   However, some Nit types are not represented by the simplest possible JSON representation.
-	#   With the added metadata, it can be complex to read.
-	#
-	# If `true`, serialize for other programs:
-	#
-	# * Nit objects are serialized to pure and standard JSON so they can
-	#   be easily read by non-Nit programs and humans.
-	# * Nit objects are serialized for every references, so they can be duplicated.
-	#   It is easier to read but it creates a larger output.
-	# * Does not support cycles, will replace the problematic references by `null`.
-	# * Does not serialize the metadata needed to deserialize the objects
-	#   back to regular Nit objects.
-	# * Keys of Nit `HashMap` are converted to their string representation using `to_s`.
-	var plain_json = false is writable
-
-	# Write pretty JSON for human eyes?
-	#
-	# Toggles skipping lines between attributes of an object and
-	# properly indent the written JSON.
-	var pretty_json = false is writable
-
-	# Current indentation level used for writing `pretty_json`
-	private var indent_level = 0
-
-	# List of the current open objects, the first is the main target of the serialization
-	#
-	# Used only when `plain_json == true` to detect cycles in serialization.
-	private var open_objects = new Array[Object]
-
-	# Has the first attribute of the current object already been serialized?
-	#
-	# Used only when `plain_json == true`.
-	private var first_attribute = false
-
-	redef fun serialize(object)
-	do
-		if object == null then
-			stream.write "null"
-		else
-			if plain_json then
-				for o in open_objects do
-					if object.is_same_serialized(o) then
-						# Cycle, can't be managed in plain json
-						warn "Cycle detected in serialized object, replacing reference with 'null'."
-						stream.write "null"
-						return
-					end
-				end
-
-				open_objects.add object
-			end
-
-			first_attribute = true
-			object.accept_json_serializer self
-			first_attribute = false
-
-			if plain_json then open_objects.pop
-		end
-	end
-
-	redef fun serialize_attribute(name, value)
-	do
-		if not plain_json or not first_attribute then
-			stream.write ","
-			first_attribute = false
-		end
-
-		new_line_and_indent
-		stream.write "\""
-		stream.write name
-		stream.write "\": "
-		super
-	end
-
-	redef fun serialize_reference(object)
-	do
-		if not plain_json and cache.has_object(object) then
-			# if already serialized, add local reference
-			var id = cache.id_for(object)
-			stream.write "\{"
-			indent_level += 1
-			new_line_and_indent
-			stream.write "\"__kind\": \"ref\", \"__id\": "
-			stream.write id.to_s
-			indent_level -= 1
-			new_line_and_indent
-			stream.write "\}"
-		else
-			# serialize here
-			serialize object
-		end
-	end
-
-	# Write a new line and indent it, only if `pretty_json`
-	private fun new_line_and_indent
-	do
-		if pretty_json then
-			stream.write "\n"
-			for i in indent_level.times do stream.write "\t"
-		end
-	end
-end
-
-# Deserializer from a Json string.
-class JsonDeserializer
-	super CachingDeserializer
-
-	# Json text to deserialize from.
-	private var text: Text
-
-	# Root json object parsed from input text.
-	private var root: nullable Object is noinit
-
-	# Depth-first path in the serialized object tree.
-	private var path = new Array[Map[String, nullable Object]]
-
-	# Names of the attributes from the root to the object currently being deserialized
-	var attributes_path = new Array[String]
-
-	# Last encountered object reference id.
-	#
-	# See `id_to_object`.
-	var just_opened_id: nullable Int = null
-
-	init do
-		var root = text.parse_json
-		if root isa Map[String, nullable Object] then path.add(root)
-		self.root = root
-	end
-
-	redef fun deserialize_attribute(name, static_type)
-	do
-		if path.is_empty then
-			# The was a parsing error or the root is not an object
-			if not root isa Error then
-				errors.add new Error("Deserialization Error: parsed JSON value is not an object.")
-			end
-			deserialize_attribute_missing = false
-			return null
-		end
-
-		var current = path.last
-
-		if not current.keys.has(name) then
-			# Let the generated code / caller of `deserialize_attribute` raise the missing attribute error
-			deserialize_attribute_missing = true
-			return null
-		end
-
-		var value = current[name]
-
-		attributes_path.add name
-		var res = convert_object(value, static_type)
-		attributes_path.pop
-
-		deserialize_attribute_missing = false
-		return res
-	end
-
-	# This may be called multiple times by the same object from constructors
-	# in different nclassdef
-	redef fun notify_of_creation(new_object)
-	do
-		var id = just_opened_id
-		if id == null then return # Register `new_object` only once
-		cache[id] = new_object
-	end
-
-	# Convert the simple JSON `object` to a Nit object
-	private fun convert_object(object: nullable Object, static_type: nullable String): nullable Object
-	do
-		if object isa JsonParseError then
-			errors.add object
-			return null
-		end
-
-		if object isa Map[String, nullable Object] then
-			var kind = null
-			if object.keys.has("__kind") then
-				kind = object["__kind"]
-			end
-
-			# ref?
-			if kind == "ref" then
-				if not object.keys.has("__id") then
-					errors.add new Error("Serialization Error: JSON object reference does not declare a `__id`.")
-					return object
-				end
-
-				var id = object["__id"]
-				if not id isa Int then
-					errors.add new Error("Serialization Error: JSON object reference declares a non-integer `__id`.")
-					return object
-				end
-
-				if not cache.has_id(id) then
-					errors.add new Error("Serialization Error: JSON object reference has an unknown `__id`.")
-					return object
-				end
-
-				return cache.object_for(id)
-			end
-
-			# obj?
-			if kind == "obj" or kind == null then
-				var id = null
-				if object.keys.has("__id") then
-					id = object["__id"]
-
-					if not id isa Int then
-						errors.add new Error("Serialization Error: JSON object declaration declares a non-integer `__id`.")
-						return object
-					end
-
-					if cache.has_id(id) then
-						errors.add new Error("Serialization Error: JSON object with `__id` {id} is deserialized twice.")
-						# Keep going
-					end
-				end
-
-				var class_name = object.get_or_null("__class")
-				if class_name == null then
-					# Fallback to custom heuristic
-					class_name = class_name_heuristic(object)
-
-					if class_name == null and static_type != null then
-						# Fallack to the static type, strip the `nullable` prefix
-						var prefix = "nullable "
-						if static_type.has(prefix) then
-							class_name = static_type.substring_from(prefix.length)
-						else class_name = static_type
-					end
-				end
-
-				if class_name == null then
-					errors.add new Error("Serialization Error: JSON object declaration does not declare a `__class`.")
-					return object
-				end
-
-				if not class_name isa String then
-					errors.add new Error("Serialization Error: JSON object declaration declares a non-string `__class`.")
-					return object
-				end
-
-				# advance on path
-				path.push object
-
-				just_opened_id = id
-				var value = deserialize_class(class_name)
-				just_opened_id = null
-
-				# revert on path
-				path.pop
-
-				return value
-			end
-
-			# char?
-			if kind == "char" then
-				if not object.keys.has("__val") then
-					errors.add new Error("Serialization Error: JSON `char` object does not declare a `__val`.")
-					return object
-				end
-
-				var val = object["__val"]
-
-				if not val isa String or val.is_empty then
-					errors.add new Error("Serialization Error: JSON `char` object does not declare a single char in `__val`.")
-					return object
-				end
-
-				return val.chars.first
-			end
-
-			errors.add new Error("Serialization Error: JSON object has an unknown `__kind`.")
-			return object
-		end
-
-		# Simple JSON array without serialization metadata
-		if object isa Array[nullable Object] then
-			# Can we use the static type?
-			if static_type != null then
-				var prefix = "nullable "
-				var class_name = if static_type.has(prefix) then
-						static_type.substring_from(prefix.length)
-					else static_type
-
-				opened_array = object
-				var value = deserialize_class(class_name)
-				opened_array = null
-				return value
-			end
-
-			# This branch should rarely be used:
-			# when an array is the root object which is accepted but illegal in standard JSON,
-			# or in strange custom deserialization hacks.
-
-			var array = new Array[nullable Object]
-			var types = new HashSet[String]
-			var has_nullable = false
-			for e in object do
-				var res = convert_object(e)
-				array.add res
-
-				if res != null then
-					types.add res.class_name
-				else has_nullable = true
-			end
-
-			if types.length == 1 then
-				var array_type = types.first
-
-				var typed_array
-				if array_type == "ASCIIFlatString" or array_type == "UnicodeFlatString" then
-					if has_nullable then
-						typed_array = new Array[nullable FlatString]
-					else typed_array = new Array[FlatString]
-				else if array_type == "Int" then
-					if has_nullable then
-						typed_array = new Array[nullable Int]
-					else typed_array = new Array[Int]
-				else if array_type == "Float" then
-					if has_nullable then
-						typed_array = new Array[nullable Float]
-					else typed_array = new Array[Float]
-				else
-					# TODO support all array types when we separate the constructor
-					# `from_deserializer` from the filling of the items.
-
-					if not has_nullable then
-						typed_array = new Array[Object]
-					else
-						# Unsupported array type, return as `Array[nullable Object]`
-						return array
-					end
-				end
-
-				assert typed_array isa Array[nullable Object]
-
-				# Copy item to the new array
-				for e in array do typed_array.add e
-				return typed_array
-			end
-
-			# Uninferrable type, return as `Array[nullable Object]`
-			return array
-		end
-
-		return object
-	end
-
-	# Current array open for deserialization, used by `SimpleCollection::from_deserializer`
-	private var opened_array: nullable Array[nullable Object] = null
-
-	redef fun deserialize
-	do
-		errors.clear
-		return convert_object(root)
-	end
-
-	# User customizable heuristic to infer the name of the Nit class to deserialize `json_object`
-	#
-	# This method is called only when deserializing an object without the metadata `__class`.
-	# Use the content of `json_object` to identify what Nit class it should be deserialized into.
-	# Or use `self.attributes_path` indicating where the deserialized object will be stored,
-	# is is less reliable as some objects don't have an associated attribute:
-	# the root/first deserialized object and collection elements.
-	#
-	# Return the class name as a `String` when it can be inferred,
-	# or `null` when the class name cannot be found.
-	#
-	# If a valid class name is returned, `json_object` will then be deserialized normally.
-	# So it must contain the attributes of the corresponding class, as usual.
-	#
-	# ~~~nitish
-	# class MyData
-	#     serialize
-	#
-	#     var data: String
-	# end
-	#
-	# class MyError
-	#     serialize
-	#
-	#     var error: String
-	#     var related_data: MyData
-	# end
-	#
-	# class MyJsonDeserializer
-	#     super JsonDeserializer
-	#
-	#     redef fun class_name_heuristic(json_object)
-	#     do
-	#         # Infer the Nit class from the content of the JSON object.
-	#         if json_object.keys.has("error") then return "MyError"
-	#         if json_object.keys.has("data") then return "MyData"
-	#
-	#         # Infer the Nit class from the attribute where it will be stored.
-	#         # This line duplicates a previous line, and would only apply when
-	#         # `MyData` is within a `MyError`.
-	#         if attributes_path.not_empty and attributes_path.last == "related_data" then return "MyData"
-	#
-	#         return null
-	#     end
-	# end
-	#
-	# var json = """{"data": "some data"}"""
-	# var deserializer = new MyJsonDeserializer(json)
-	# var deserialized = deserializer.deserialize
-	# assert deserialized isa MyData
-	#
-	# json = """{"error": "some error message",
-	#            "related_data": {"data": "some other data"}"""
-	# deserializer = new MyJsonDeserializer(json)
-	# deserialized = deserializer.deserialize
-	# assert deserialized isa MyError
-	# ~~~
-	protected fun class_name_heuristic(json_object: Map[String, nullable Object]): nullable String
-	do
-		return null
-	end
-end
-
-redef class Text
-
-	# Deserialize a `nullable Object` from this JSON formatted string
-	#
-	# Warning: Deserialization errors are reported with `print_error` and
-	# may be returned as a partial object or as `null`.
-	#
-	# This method is not appropriate when errors need to be handled programmatically,
-	# manually use a `JsonDeserializer` in such cases.
-	fun from_json_string: nullable Object
-	do
-		var deserializer = new JsonDeserializer(self)
-		var res = deserializer.deserialize
-		if deserializer.errors.not_empty then
-			print_error "Deserialization Errors: {deserializer.errors.join(", ")}"
-		end
-		return res
-	end
-
-	redef fun accept_json_serializer(v) do v.stream.write(to_json)
-end
-
-redef class Serializable
-
-	# Serialize `self` to JSON
-	#
-	# Set `plain = true` to generate standard JSON, without deserialization metadata.
-	# Use this option if the generated JSON will be read by other programs or humans.
-	# Use the default, `plain = false`, if the JSON is to be deserialized by a Nit program.
-	#
-	# Set `pretty = true` to generate pretty JSON for human eyes.
-	# Use the default, `pretty = false`, to generate minified JSON.
-	#
-	# This method should not be refined by subclasses,
-	# instead `accept_json_serializer` can customize the serialization of an object.
-	#
-	# See: `JsonSerializer`
-	fun serialize_to_json(plain, pretty: nullable Bool): String
-	do
-		var stream = new StringWriter
-		var serializer = new JsonSerializer(stream)
-		serializer.plain_json = plain or else false
-		serializer.pretty_json = pretty or else false
-		serializer.serialize self
-		stream.close
-		return stream.to_s
-	end
-
-	# Refinable service to customize the serialization of this class to JSON
-	#
-	# This method can be refined to customize the serialization by either
-	# writing pure JSON directly on the stream `v.stream` or
-	# by using other services of `JsonSerializer`.
-	#
-	# Most of the time, it is preferable to refine the method `core_serialize_to`
-	# which is used by all the serialization engines, not just JSON.
-	protected fun accept_json_serializer(v: JsonSerializer)
-	do
-		var id = v.cache.new_id_for(self)
-		v.stream.write "\{"
-		v.indent_level += 1
-		if not v.plain_json then
-			v.new_line_and_indent
-			v.stream.write "\"__kind\": \"obj\", \"__id\": "
-			v.stream.write id.to_s
-			v.stream.write ", \"__class\": \""
-			v.stream.write class_name
-			v.stream.write "\""
-		end
-		core_serialize_to(v)
-
-		v.indent_level -= 1
-		v.new_line_and_indent
-		v.stream.write "\}"
-	end
-end
-
-redef class Int
-	redef fun accept_json_serializer(v) do v.stream.write to_s
-end
-
-redef class Float
-	redef fun accept_json_serializer(v) do v.stream.write to_s
-end
-
-redef class Bool
-	redef fun accept_json_serializer(v) do v.stream.write to_s
-end
-
-redef class Char
-	redef fun accept_json_serializer(v)
-	do
-		if v.plain_json then
-			to_s.accept_json_serializer v
-		else
-			v.stream.write "\{\"__kind\": \"char\", \"__val\": "
-			to_s.accept_json_serializer v
-			v.stream.write "\}"
-		end
-	end
-end
-
-redef class NativeString
-	redef fun accept_json_serializer(v) do to_s.accept_json_serializer(v)
-end
-
-redef class Collection[E]
-	# Utility to serialize a normal Json array
-	private fun serialize_to_pure_json(v: JsonSerializer)
-	do
-		v.stream.write "["
-		v.indent_level += 1
-		var is_first = true
-		for e in self do
-			if is_first then
-				is_first = false
-			else v.stream.write ","
-			v.new_line_and_indent
-
-			if not v.try_to_serialize(e) then
-				assert e != null # null would have been serialized
-				v.warn("element of type {e.class_name} is not serializable.")
-			end
-		end
-		v.indent_level -= 1
-		v.new_line_and_indent
-		v.stream.write "]"
-	end
-end
-
-redef class SimpleCollection[E]
-	redef fun accept_json_serializer(v)
-	do
-		# Register as pseudo object
-		if not v.plain_json then
-			var id = v.cache.new_id_for(self)
-			v.stream.write """{"""
-			v.indent_level += 1
-			v.new_line_and_indent
-			v.stream.write """"__kind": "obj", "__id": """
-			v.stream.write id.to_s
-			v.stream.write """, "__class": """"
-			v.stream.write class_name
-			v.stream.write """","""
-			v.new_line_and_indent
-			v.stream.write """"__items": """
-
-			core_serialize_to v
-		end
-
-		serialize_to_pure_json v
-
-		if not v.plain_json then
-			v.indent_level -= 1
-			v.new_line_and_indent
-			v.stream.write "\}"
-		end
-	end
-
-	redef init from_deserializer(v)
-	do
-		super
-		if v isa JsonDeserializer then
-			v.notify_of_creation self
-			init
-
-			var open_array: nullable SequenceRead[nullable Object] = v.opened_array
-			if open_array == null then
-				# With metadata
-				var arr = v.path.last.get_or_null("__items")
-				if not arr isa SequenceRead[nullable Object] then
-					# If there is nothing, we consider that it is an empty collection.
-					if arr != null then v.errors.add new Error("Deserialization Error: invalid format in {self.class_name}")
-					return
-				end
-				open_array = arr
-			end
-
-			# Try to get the name of the single parameter type assuming it is E.
-			# This does not work in non-generic subclasses,
-			# when the first parameter is not E, or
-			# when there is more than one parameter. (The last one could be fixed)
-			var class_name = class_name
-			var items_type = null
-			var bracket_index = class_name.index_of('[')
-			if bracket_index != -1 then
-				var start = bracket_index + 1
-				var ending = class_name.last_index_of(']')
-				items_type = class_name.substring(start, ending-start)
-			end
-
-			# Fill array
-			for o in open_array do
-				var obj = v.convert_object(o, items_type)
-				if obj isa E then
-					add obj
-				else v.errors.add new AttributeTypeError(self, "items", obj, "E")
-			end
-		end
-	end
-end
-
-redef class Map[K, V]
-	redef fun accept_json_serializer(v)
-	do
-		# Register as pseudo object
-		var id = v.cache.new_id_for(self)
-
-		v.stream.write "\{"
-		v.indent_level += 1
-
-		if v.plain_json then
-			var first = true
-			for key, val in self do
-				if not first then
-					v.stream.write ","
-				else first = false
-				v.new_line_and_indent
-
-				var k = key or else "null"
-				k.to_s.accept_json_serializer v
-				v.stream.write ": "
-				if not v.try_to_serialize(val) then
-					assert val != null # null would have been serialized
-					v.warn("element of type {val.class_name} is not serializable.")
-					v.stream.write "null"
-				end
-			end
-		else
-			v.new_line_and_indent
-			v.stream.write """"__kind": "obj", "__id": """
-			v.stream.write id.to_s
-			v.stream.write """, "__class": """"
-			v.stream.write class_name
-			v.stream.write """", "__length": """
-			v.stream.write length.to_s
-
-			v.stream.write ","
-			v.new_line_and_indent
-			v.stream.write """"__keys": """
-			keys.serialize_to_pure_json v
-
-			v.stream.write ","
-			v.new_line_and_indent
-			v.stream.write """"__values": """
-			values.serialize_to_pure_json v
-
-			core_serialize_to v
-		end
-
-		v.indent_level -= 1
-		v.new_line_and_indent
-		v.stream.write "\}"
-	end
-
-	redef init from_deserializer(v)
-	do
-		super
-
-		if v isa JsonDeserializer then
-			v.notify_of_creation self
-			init
-
-			var length = v.deserialize_attribute("__length")
-			var keys = v.path.last.get_or_null("__keys")
-			var values = v.path.last.get_or_null("__values")
-
-			# Length is optional
-			if length == null and keys isa SequenceRead[nullable Object] then length = keys.length
-
-			# Consistency check
-			if not length isa Int or length < 0 or
-			   not keys isa SequenceRead[nullable Object] or
-			   not values isa SequenceRead[nullable Object] or
-			   keys.length != values.length or length != keys.length then
-
-				# If there is nothing or length == 0, we consider that it is an empty Map.
-				if (length != null and length != 0) or keys != null or values != null then
-					v.errors.add new Error("Deserialization Error: invalid format in {self.class_name}")
-				end
-				return
-			end
-
-			for i in length.times do
-				var key = v.convert_object(keys[i])
-				var value = v.convert_object(values[i])
-
-				if not key isa K then
-					v.errors.add new AttributeTypeError(self, "keys", key, "K")
-					continue
-				end
-
-				if not value isa V then
-					v.errors.add new AttributeTypeError(self, "values", value, "V")
-					continue
-				end
-
-				if has_key(key) then
-					v.errors.add new Error("Deserialization Error: duplicated key '{key or else "null"}' in {self.class_name}, previous value overwritten")
-				end
-
-				self[key] = value
-			end
-		end
-	end
-end
diff --git a/lib/json/serialization_read.nit b/lib/json/serialization_read.nit
new file mode 100644
index 0000000000..e29f5bde8a
--- /dev/null
+++ b/lib/json/serialization_read.nit
@@ -0,0 +1,460 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Services to read JSON: `from_json_string` and `JsonDeserializer`
+module serialization_read
+
+import ::serialization::caching
+private import ::serialization::engine_tools
+private import static
+private import string_parser
+
+# Deserializer from a Json string.
+class JsonDeserializer
+	super CachingDeserializer
+
+	# Json text to deserialize from.
+	private var text: Text
+
+	# Root json object parsed from input text.
+	private var root: nullable Object is noinit
+
+	# Depth-first path in the serialized object tree.
+	private var path = new Array[Map[String, nullable Object]]
+
+	# Names of the attributes from the root to the object currently being deserialized
+	var attributes_path = new Array[String]
+
+	# Last encountered object reference id.
+	#
+	# See `id_to_object`.
+	var just_opened_id: nullable Int = null
+
+	init do
+		var root = text.parse_json
+		if root isa Map[String, nullable Object] then path.add(root)
+		self.root = root
+	end
+
+	redef fun deserialize_attribute(name, static_type)
+	do
+		if path.is_empty then
+			# The was a parsing error or the root is not an object
+			if not root isa Error then
+				errors.add new Error("Deserialization Error: parsed JSON value is not an object.")
+			end
+			deserialize_attribute_missing = false
+			return null
+		end
+
+		var current = path.last
+
+		if not current.keys.has(name) then
+			# Let the generated code / caller of `deserialize_attribute` raise the missing attribute error
+			deserialize_attribute_missing = true
+			return null
+		end
+
+		var value = current[name]
+
+		attributes_path.add name
+		var res = convert_object(value, static_type)
+		attributes_path.pop
+
+		deserialize_attribute_missing = false
+		return res
+	end
+
+	# This may be called multiple times by the same object from constructors
+	# in different nclassdef
+	redef fun notify_of_creation(new_object)
+	do
+		var id = just_opened_id
+		if id == null then return # Register `new_object` only once
+		cache[id] = new_object
+	end
+
+	# Convert the simple JSON `object` to a Nit object
+	private fun convert_object(object: nullable Object, static_type: nullable String): nullable Object
+	do
+		if object isa JsonParseError then
+			errors.add object
+			return null
+		end
+
+		if object isa Map[String, nullable Object] then
+			var kind = null
+			if object.keys.has("__kind") then
+				kind = object["__kind"]
+			end
+
+			# ref?
+			if kind == "ref" then
+				if not object.keys.has("__id") then
+					errors.add new Error("Serialization Error: JSON object reference does not declare a `__id`.")
+					return object
+				end
+
+				var id = object["__id"]
+				if not id isa Int then
+					errors.add new Error("Serialization Error: JSON object reference declares a non-integer `__id`.")
+					return object
+				end
+
+				if not cache.has_id(id) then
+					errors.add new Error("Serialization Error: JSON object reference has an unknown `__id`.")
+					return object
+				end
+
+				return cache.object_for(id)
+			end
+
+			# obj?
+			if kind == "obj" or kind == null then
+				var id = null
+				if object.keys.has("__id") then
+					id = object["__id"]
+
+					if not id isa Int then
+						errors.add new Error("Serialization Error: JSON object declaration declares a non-integer `__id`.")
+						return object
+					end
+
+					if cache.has_id(id) then
+						errors.add new Error("Serialization Error: JSON object with `__id` {id} is deserialized twice.")
+						# Keep going
+					end
+				end
+
+				var class_name = object.get_or_null("__class")
+				if class_name == null then
+					# Fallback to custom heuristic
+					class_name = class_name_heuristic(object)
+
+					if class_name == null and static_type != null then
+						# Fallack to the static type, strip the `nullable` prefix
+						var prefix = "nullable "
+						if static_type.has(prefix) then
+							class_name = static_type.substring_from(prefix.length)
+						else class_name = static_type
+					end
+				end
+
+				if class_name == null then
+					errors.add new Error("Serialization Error: JSON object declaration does not declare a `__class`.")
+					return object
+				end
+
+				if not class_name isa String then
+					errors.add new Error("Serialization Error: JSON object declaration declares a non-string `__class`.")
+					return object
+				end
+
+				# advance on path
+				path.push object
+
+				just_opened_id = id
+				var value = deserialize_class(class_name)
+				just_opened_id = null
+
+				# revert on path
+				path.pop
+
+				return value
+			end
+
+			# char?
+			if kind == "char" then
+				if not object.keys.has("__val") then
+					errors.add new Error("Serialization Error: JSON `char` object does not declare a `__val`.")
+					return object
+				end
+
+				var val = object["__val"]
+
+				if not val isa String or val.is_empty then
+					errors.add new Error("Serialization Error: JSON `char` object does not declare a single char in `__val`.")
+					return object
+				end
+
+				return val.chars.first
+			end
+
+			errors.add new Error("Serialization Error: JSON object has an unknown `__kind`.")
+			return object
+		end
+
+		# Simple JSON array without serialization metadata
+		if object isa Array[nullable Object] then
+			# Can we use the static type?
+			if static_type != null then
+				var prefix = "nullable "
+				var class_name = if static_type.has(prefix) then
+						static_type.substring_from(prefix.length)
+					else static_type
+
+				opened_array = object
+				var value = deserialize_class(class_name)
+				opened_array = null
+				return value
+			end
+
+			# This branch should rarely be used:
+			# when an array is the root object which is accepted but illegal in standard JSON,
+			# or in strange custom deserialization hacks.
+
+			var array = new Array[nullable Object]
+			var types = new HashSet[String]
+			var has_nullable = false
+			for e in object do
+				var res = convert_object(e)
+				array.add res
+
+				if res != null then
+					types.add res.class_name
+				else has_nullable = true
+			end
+
+			if types.length == 1 then
+				var array_type = types.first
+
+				var typed_array
+				if array_type == "ASCIIFlatString" or array_type == "UnicodeFlatString" then
+					if has_nullable then
+						typed_array = new Array[nullable FlatString]
+					else typed_array = new Array[FlatString]
+				else if array_type == "Int" then
+					if has_nullable then
+						typed_array = new Array[nullable Int]
+					else typed_array = new Array[Int]
+				else if array_type == "Float" then
+					if has_nullable then
+						typed_array = new Array[nullable Float]
+					else typed_array = new Array[Float]
+				else
+					# TODO support all array types when we separate the constructor
+					# `from_deserializer` from the filling of the items.
+
+					if not has_nullable then
+						typed_array = new Array[Object]
+					else
+						# Unsupported array type, return as `Array[nullable Object]`
+						return array
+					end
+				end
+
+				assert typed_array isa Array[nullable Object]
+
+				# Copy item to the new array
+				for e in array do typed_array.add e
+				return typed_array
+			end
+
+			# Uninferrable type, return as `Array[nullable Object]`
+			return array
+		end
+
+		return object
+	end
+
+	# Current array open for deserialization, used by `SimpleCollection::from_deserializer`
+	private var opened_array: nullable Array[nullable Object] = null
+
+	redef fun deserialize
+	do
+		errors.clear
+		return convert_object(root)
+	end
+
+	# User customizable heuristic to infer the name of the Nit class to deserialize `json_object`
+	#
+	# This method is called only when deserializing an object without the metadata `__class`.
+	# Use the content of `json_object` to identify what Nit class it should be deserialized into.
+	# Or use `self.attributes_path` indicating where the deserialized object will be stored,
+	# is is less reliable as some objects don't have an associated attribute:
+	# the root/first deserialized object and collection elements.
+	#
+	# Return the class name as a `String` when it can be inferred,
+	# or `null` when the class name cannot be found.
+	#
+	# If a valid class name is returned, `json_object` will then be deserialized normally.
+	# So it must contain the attributes of the corresponding class, as usual.
+	#
+	# ~~~
+	# class MyData
+	#     serialize
+	#
+	#     var data: String
+	# end
+	#
+	# class MyError
+	#     serialize
+	#
+	#     var error: String
+	#     var related_data: MyData
+	# end
+	#
+	# class MyJsonDeserializer
+	#     super JsonDeserializer
+	#
+	#     redef fun class_name_heuristic(json_object)
+	#     do
+	#         # Infer the Nit class from the content of the JSON object.
+	#         if json_object.keys.has("error") then return "MyError"
+	#         if json_object.keys.has("data") then return "MyData"
+	#
+	#         # Infer the Nit class from the attribute where it will be stored.
+	#         # This line duplicates a previous line, and would only apply when
+	#         # `MyData` is within a `MyError`.
+	#         if attributes_path.not_empty and attributes_path.last == "related_data" then return "MyData"
+	#
+	#         return null
+	#     end
+	# end
+	#
+	# var json = """{"data": "some data"}"""
+	# var deserializer = new MyJsonDeserializer(json)
+	# var deserialized = deserializer.deserialize
+	# assert deserializer.errors.is_empty
+	# assert deserialized isa MyData
+	#
+	# json = """{"error": "some error message",
+	#            "related_data": {"data": "some other data"}}"""
+	# deserializer = new MyJsonDeserializer(json)
+	# deserialized = deserializer.deserialize
+	# assert deserializer.errors.is_empty
+	# assert deserialized isa MyError
+	# ~~~
+	protected fun class_name_heuristic(json_object: Map[String, nullable Object]): nullable String
+	do
+		return null
+	end
+end
+
+redef class Text
+
+	# Deserialize a `nullable Object` from this JSON formatted string
+	#
+	# Warning: Deserialization errors are reported with `print_error` and
+	# may be returned as a partial object or as `null`.
+	#
+	# This method is not appropriate when errors need to be handled programmatically,
+	# manually use a `JsonDeserializer` in such cases.
+	fun from_json_string: nullable Object
+	do
+		var deserializer = new JsonDeserializer(self)
+		var res = deserializer.deserialize
+		if deserializer.errors.not_empty then
+			print_error "Deserialization Errors: {deserializer.errors.join(", ")}"
+		end
+		return res
+	end
+end
+
+redef class SimpleCollection[E]
+	redef init from_deserializer(v)
+	do
+		super
+		if v isa JsonDeserializer then
+			v.notify_of_creation self
+			init
+
+			var open_array: nullable SequenceRead[nullable Object] = v.opened_array
+			if open_array == null then
+				# With metadata
+				var arr = v.path.last.get_or_null("__items")
+				if not arr isa SequenceRead[nullable Object] then
+					# If there is nothing, we consider that it is an empty collection.
+					if arr != null then v.errors.add new Error("Deserialization Error: invalid format in {self.class_name}")
+					return
+				end
+				open_array = arr
+			end
+
+			# Try to get the name of the single parameter type assuming it is E.
+			# This does not work in non-generic subclasses,
+			# when the first parameter is not E, or
+			# when there is more than one parameter. (The last one could be fixed)
+			var class_name = class_name
+			var items_type = null
+			var bracket_index = class_name.index_of('[')
+			if bracket_index != -1 then
+				var start = bracket_index + 1
+				var ending = class_name.last_index_of(']')
+				items_type = class_name.substring(start, ending-start)
+			end
+
+			# Fill array
+			for o in open_array do
+				var obj = v.convert_object(o, items_type)
+				if obj isa E then
+					add obj
+				else v.errors.add new AttributeTypeError(self, "items", obj, "E")
+			end
+		end
+	end
+end
+
+redef class Map[K, V]
+	redef init from_deserializer(v)
+	do
+		super
+
+		if v isa JsonDeserializer then
+			v.notify_of_creation self
+			init
+
+			var length = v.deserialize_attribute("__length")
+			var keys = v.path.last.get_or_null("__keys")
+			var values = v.path.last.get_or_null("__values")
+
+			# Length is optional
+			if length == null and keys isa SequenceRead[nullable Object] then length = keys.length
+
+			# Consistency check
+			if not length isa Int or length < 0 or
+			   not keys isa SequenceRead[nullable Object] or
+			   not values isa SequenceRead[nullable Object] or
+			   keys.length != values.length or length != keys.length then
+
+				# If there is nothing or length == 0, we consider that it is an empty Map.
+				if (length != null and length != 0) or keys != null or values != null then
+					v.errors.add new Error("Deserialization Error: invalid format in {self.class_name}")
+				end
+				return
+			end
+
+			for i in length.times do
+				var key = v.convert_object(keys[i])
+				var value = v.convert_object(values[i])
+
+				if not key isa K then
+					v.errors.add new AttributeTypeError(self, "keys", key, "K")
+					continue
+				end
+
+				if not value isa V then
+					v.errors.add new AttributeTypeError(self, "values", value, "V")
+					continue
+				end
+
+				if has_key(key) then
+					v.errors.add new Error("Deserialization Error: duplicated key '{key or else "null"}' in {self.class_name}, previous value overwritten")
+				end
+
+				self[key] = value
+			end
+		end
+	end
+end
diff --git a/lib/json/serialization_write.nit b/lib/json/serialization_write.nit
new file mode 100644
index 0000000000..e26236cb2a
--- /dev/null
+++ b/lib/json/serialization_write.nit
@@ -0,0 +1,371 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Services to write Nit objects to JSON strings: `serialize_to_json` and `JsonSerializer`
+module serialization_write
+
+import ::serialization::caching
+private import ::serialization::engine_tools
+
+# Serializer of Nit objects to Json string.
+class JsonSerializer
+	super CachingSerializer
+
+	# Target writing stream
+	var stream: Writer
+
+	# Write plain JSON? Standard JSON without metadata for deserialization
+	#
+	# If `false`, the default, serialize to support deserialization:
+	#
+	# * Write metadata, including the types of the serialized objects so they can
+	#   be deserialized to their original form using `JsonDeserializer`.
+	# * Use references when an object has already been serialized so to not duplicate it.
+	# * Support cycles in references.
+	# * Preserve the Nit `Char` type as an object because it does not exist in JSON.
+	# * The generated JSON is standard and can be read by non-Nit programs.
+	#   However, some Nit types are not represented by the simplest possible JSON representation.
+	#   With the added metadata, it can be complex to read.
+	#
+	# If `true`, serialize for other programs:
+	#
+	# * Nit objects are serialized to pure and standard JSON so they can
+	#   be easily read by non-Nit programs and humans.
+	# * Nit objects are serialized for every references, so they can be duplicated.
+	#   It is easier to read but it creates a larger output.
+	# * Does not support cycles, will replace the problematic references by `null`.
+	# * Does not serialize the metadata needed to deserialize the objects
+	#   back to regular Nit objects.
+	# * Keys of Nit `HashMap` are converted to their string representation using `to_s`.
+	var plain_json = false is writable
+
+	# Write pretty JSON for human eyes?
+	#
+	# Toggles skipping lines between attributes of an object and
+	# properly indent the written JSON.
+	var pretty_json = false is writable
+
+	# Current indentation level used for writing `pretty_json`
+	private var indent_level = 0
+
+	# List of the current open objects, the first is the main target of the serialization
+	#
+	# Used only when `plain_json == true` to detect cycles in serialization.
+	private var open_objects = new Array[Object]
+
+	# Has the first attribute of the current object already been serialized?
+	#
+	# Used only when `plain_json == true`.
+	private var first_attribute = false
+
+	redef fun serialize(object)
+	do
+		if object == null then
+			stream.write "null"
+		else
+			if plain_json then
+				for o in open_objects do
+					if object.is_same_serialized(o) then
+						# Cycle, can't be managed in plain json
+						warn "Cycle detected in serialized object, replacing reference with 'null'."
+						stream.write "null"
+						return
+					end
+				end
+
+				open_objects.add object
+			end
+
+			first_attribute = true
+			object.accept_json_serializer self
+			first_attribute = false
+
+			if plain_json then open_objects.pop
+		end
+	end
+
+	redef fun serialize_attribute(name, value)
+	do
+		if not plain_json or not first_attribute then
+			stream.write ","
+			first_attribute = false
+		end
+
+		new_line_and_indent
+		stream.write "\""
+		stream.write name
+		stream.write "\":"
+		if pretty_json then stream.write " "
+		super
+	end
+
+	redef fun serialize_reference(object)
+	do
+		if not plain_json and cache.has_object(object) then
+			# if already serialized, add local reference
+			var id = cache.id_for(object)
+			stream.write "\{"
+			indent_level += 1
+			new_line_and_indent
+			stream.write "\"__kind\": \"ref\", \"__id\": "
+			stream.write id.to_s
+			indent_level -= 1
+			new_line_and_indent
+			stream.write "\}"
+		else
+			# serialize here
+			serialize object
+		end
+	end
+
+	# Write a new line and indent it, only if `pretty_json`
+	private fun new_line_and_indent
+	do
+		if pretty_json then
+			stream.write "\n"
+			for i in indent_level.times do stream.write "\t"
+		end
+	end
+end
+
+redef class Text
+
+	redef fun accept_json_serializer(v)
+	do
+		v.stream.write "\""
+		for i in [0 .. self.length[ do
+			var char = self[i]
+			if char == '\\' then
+				v.stream.write "\\\\"
+			else if char == '\"' then
+				v.stream.write "\\\""
+			else if char < ' ' then
+				if char == '\n' then
+					v.stream.write "\\n"
+				else if char == '\r' then
+					v.stream.write "\\r"
+				else if char == '\t' then
+					v.stream.write "\\t"
+				else
+					v.stream.write char.escape_to_utf16
+				end
+			else
+				v.stream.write char.to_s
+			end
+		end
+		v.stream.write "\""
+	end
+end
+
+redef class Serializable
+
+	# Serialize `self` to JSON
+	#
+	# Set `plain = true` to generate standard JSON, without deserialization metadata.
+	# Use this option if the generated JSON will be read by other programs or humans.
+	# Use the default, `plain = false`, if the JSON is to be deserialized by a Nit program.
+	#
+	# Set `pretty = true` to generate pretty JSON for human eyes.
+	# Use the default, `pretty = false`, to generate minified JSON.
+	#
+	# This method should not be refined by subclasses,
+	# instead `accept_json_serializer` can customize the serialization of an object.
+	#
+	# See: `JsonSerializer`
+	fun serialize_to_json(plain, pretty: nullable Bool): String
+	do
+		var stream = new StringWriter
+		var serializer = new JsonSerializer(stream)
+		serializer.plain_json = plain or else false
+		serializer.pretty_json = pretty or else false
+		serializer.serialize self
+		stream.close
+		return stream.to_s
+	end
+
+	# Serialize `self` to plain JSON
+	#
+	# Compatibility alias for `serialize_to_json(plain=true)`.
+	fun to_json: String do return serialize_to_json(plain=true)
+
+	# Serialize `self` to plain pretty JSON
+	#
+	# Compatibility alias for `serialize_to_json(plain=true, pretty=true)`.
+	fun to_pretty_json: String do return serialize_to_json(plain=true, pretty=true)
+
+	# Refinable service to customize the serialization of this class to JSON
+	#
+	# This method can be refined to customize the serialization by either
+	# writing pure JSON directly on the stream `v.stream` or
+	# by using other services of `JsonSerializer`.
+	#
+	# Most of the time, it is preferable to refine the method `core_serialize_to`
+	# which is used by all the serialization engines, not just JSON.
+	protected fun accept_json_serializer(v: JsonSerializer)
+	do
+		var id = v.cache.new_id_for(self)
+		v.stream.write "\{"
+		v.indent_level += 1
+		if not v.plain_json then
+			v.new_line_and_indent
+			v.stream.write "\"__kind\": \"obj\", \"__id\": "
+			v.stream.write id.to_s
+			v.stream.write ", \"__class\": \""
+			v.stream.write class_name
+			v.stream.write "\""
+		end
+		core_serialize_to(v)
+
+		v.indent_level -= 1
+		v.new_line_and_indent
+		v.stream.write "\}"
+	end
+end
+
+redef class Int
+	redef fun accept_json_serializer(v) do v.stream.write to_s
+end
+
+redef class Float
+	redef fun accept_json_serializer(v) do v.stream.write to_s
+end
+
+redef class Bool
+	redef fun accept_json_serializer(v) do v.stream.write to_s
+end
+
+redef class Char
+	redef fun accept_json_serializer(v)
+	do
+		if v.plain_json then
+			to_s.accept_json_serializer v
+		else
+			v.stream.write "\{\"__kind\": \"char\", \"__val\": "
+			to_s.accept_json_serializer v
+			v.stream.write "\}"
+		end
+	end
+end
+
+redef class NativeString
+	redef fun accept_json_serializer(v) do to_s.accept_json_serializer(v)
+end
+
+redef class Collection[E]
+	# Utility to serialize a normal Json array
+	private fun serialize_to_pure_json(v: JsonSerializer)
+	do
+		v.stream.write "["
+		var is_first = true
+		for e in self do
+			if is_first then
+				is_first = false
+			else
+				v.stream.write ","
+				if v.pretty_json then v.stream.write " "
+			end
+
+			if not v.try_to_serialize(e) then
+				assert e != null # null would have been serialized
+				v.warn("element of type {e.class_name} is not serializable.")
+			end
+		end
+		v.stream.write "]"
+	end
+end
+
+redef class SimpleCollection[E]
+	redef fun accept_json_serializer(v)
+	do
+		# Register as pseudo object
+		if not v.plain_json then
+			var id = v.cache.new_id_for(self)
+			v.stream.write """{"""
+			v.indent_level += 1
+			v.new_line_and_indent
+			v.stream.write """"__kind": "obj", "__id": """
+			v.stream.write id.to_s
+			v.stream.write """, "__class": """"
+			v.stream.write class_name
+			v.stream.write """","""
+			v.new_line_and_indent
+			v.stream.write """"__items": """
+
+			core_serialize_to v
+		end
+
+		serialize_to_pure_json v
+
+		if not v.plain_json then
+			v.indent_level -= 1
+			v.new_line_and_indent
+			v.stream.write "\}"
+		end
+	end
+end
+
+redef class Map[K, V]
+	redef fun accept_json_serializer(v)
+	do
+		# Register as pseudo object
+		var id = v.cache.new_id_for(self)
+
+		v.stream.write "\{"
+		v.indent_level += 1
+
+		if v.plain_json then
+			var first = true
+			for key, val in self do
+				if not first then
+					v.stream.write ","
+				else first = false
+				v.new_line_and_indent
+
+				var k = key or else "null"
+				k.to_s.accept_json_serializer v
+				v.stream.write ":"
+				if v.pretty_json then v.stream.write " "
+				if not v.try_to_serialize(val) then
+					assert val != null # null would have been serialized
+					v.warn("element of type {val.class_name} is not serializable.")
+					v.stream.write "null"
+				end
+			end
+		else
+			v.new_line_and_indent
+			v.stream.write """"__kind": "obj", "__id": """
+			v.stream.write id.to_s
+			v.stream.write """, "__class": """"
+			v.stream.write class_name
+			v.stream.write """", "__length": """
+			v.stream.write length.to_s
+
+			v.stream.write ","
+			v.new_line_and_indent
+			v.stream.write """"__keys": """
+			keys.serialize_to_pure_json v
+
+			v.stream.write ","
+			v.new_line_and_indent
+			v.stream.write """"__values": """
+			values.serialize_to_pure_json v
+
+			core_serialize_to v
+		end
+
+		v.indent_level -= 1
+		v.new_line_and_indent
+		v.stream.write "\}"
+	end
+end
diff --git a/lib/json/static.nit b/lib/json/static.nit
index dd1cc85093..f3107cce92 100644
--- a/lib/json/static.nit
+++ b/lib/json/static.nit
@@ -16,11 +16,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Static interface to get Nit objects from a Json string.
+# Static interface to read Nit objects from JSON strings
 #
-# `Text::parse_json` returns an equivalent Nit object from
-# the Json source. This object can then be type checked by the usual
-# languages features (`isa` and `as`).
+# `Text::parse_json` returns a simple Nit object from the JSON source.
+# This object can then be type checked as usual with `isa` and `as`.
 module static
 
 import error
@@ -29,64 +28,7 @@ private import json_lexer
 
 # Something that can be translated to JSON.
 interface Jsonable
-	# Encode `self` in JSON.
-	#
-	# This is a recursive method which can be refined by any subclasses.
-	# To write any `Serializable` object to JSON, see `serialize_to_json`.
-	#
-	# SEE: `append_json`
-	fun to_json: String is abstract
-
-	# Use `append_json` to implement `to_json`.
-	#
-	# Therefore, one that redefine `append_json` may use the following
-	# redefinition to link `to_json` and `append_json`:
-	#
-	# ~~~nitish
-	# redef fun to_json do return to_json_by_append
-	# ~~~
-	#
-	# Note: This is not the default implementation of `to_json` in order to
-	# avoid cyclic references between `append_json` and `to_json` when none are
-	# implemented.
-	protected fun to_json_by_append: String do
-		var buffer = new FlatBuffer
-		append_json(buffer)
-		return buffer.to_s
-	end
-
-	# Append the JSON representation of `self` to the specified buffer.
-	#
-	# SEE: `to_json`
-	fun append_json(buffer: Buffer) do buffer.append(to_json)
-
-	# Pretty print JSON string.
-	#
-	# ~~~
-	# var obj = new JsonObject
-	# obj["foo"] = 1
-	# obj["bar"] = true
-	# var arr = new JsonArray
-	# arr.add 2
-	# arr.add false
-	# arr.add "baz"
-	# obj["baz"] = arr
-	# var res = obj.to_pretty_json
-	# var exp = """{
-	# \t"foo": 1,
-	# \t"bar": true,
-	# \t"baz": [2, false, "baz"]
-	# }\n"""
-	# assert res == exp
-	# ~~~
-	fun to_pretty_json: String do
-		var res = new FlatBuffer
-		pretty_json_visit(res, 0)
-		res.add '\n'
-		return res.to_s
-	end
-
-	private fun pretty_json_visit(buffer: FlatBuffer, indent: Int) is abstract
+	super Serializable
 end
 
 redef class Text
@@ -108,31 +50,6 @@ redef class Text
 	#     assert "\\\"string\\\"".json_need_escape
 	protected fun json_need_escape: Bool do return has('\\')
 
-	redef fun append_json(buffer) do
-		buffer.add '\"'
-		for i in [0 .. self.length[ do
-			var char = self[i]
-			if char == '\\' then
-				buffer.append "\\\\"
-			else if char == '\"' then
-				buffer.append "\\\""
-			else if char < ' ' then
-				if char == '\n' then
-					buffer.append "\\n"
-				else if char == '\r' then
-					buffer.append "\\r"
-				else if char == '\t' then
-					buffer.append "\\t"
-				else
-					buffer.append char.escape_to_utf16
-				end
-			else
-				buffer.add char
-			end
-		end
-		buffer.add '\"'
-	end
-
 	# Escapes `self` from a JSON string to a Nit string
 	#
 	#     assert "\\\"string\\\"".json_to_nit_string == "\"string\""
@@ -180,19 +97,6 @@ redef class Text
 		return res.to_s
 	end
 
-
-	# Encode `self` in JSON.
-	#
-	# ~~~
-	# assert "\t\"http://example.com\"\r\n\0\\".to_json ==
-	#     "\"\\t\\\"http://example.com\\\"\\r\\n\\u0000\\\\\""
-	# ~~~
-	redef fun to_json do
-		var b = new FlatBuffer.with_capacity(byte_length)
-		append_json(b)
-		return b.to_s
-	end
-
 	# Parse `self` as JSON.
 	#
 	# If `self` is not a valid JSON document or contains an unsupported escape
@@ -248,116 +152,22 @@ redef class FlatText
 	end
 end
 
-redef class Buffer
-
-	# Append the JSON representation of `jsonable` to `self`.
-	#
-	# Append `"null"` for `null`.
-	private fun append_json_of(jsonable: nullable Jsonable) do
-		if jsonable isa Jsonable then
-			append jsonable.to_json
-		else
-			append "null"
-		end
-	end
-end
-
 redef class Int
 	super Jsonable
-
-	# Encode `self` in JSON.
-	#
-	#     assert 0.to_json == "0"
-	#     assert (-42).to_json == "-42"
-	redef fun to_json do return self.to_s
 end
 
 redef class Float
 	super Jsonable
-
-	# Encode `self` in JSON.
-	#
-	# Note: Because this method use `to_s`, it may lose precision.
-	#
-	# ~~~
-	# # Will not work as expected.
-	# # assert (-0.0).to_json == "-0.0"
-	#
-	# assert (.5).to_json == "0.5"
-	# assert (0.0).to_json == "0.0"
-	# ~~~
-	redef fun to_json do return self.to_s
 end
 
 redef class Bool
 	super Jsonable
-
-	# Encode `self` in JSON.
-	#
-	#     assert true.to_json == "true"
-	#     assert false.to_json == "false"
-	redef fun to_json do return self.to_s
 end
 
 # A map that can be translated into a JSON object.
 interface JsonMapRead[K: String, V: nullable Jsonable]
 	super MapRead[K, V]
 	super Jsonable
-
-	redef fun append_json(buffer) do
-		buffer.append "\{"
-		var it = iterator
-		if it.is_ok then
-			append_json_entry(it, buffer)
-			while it.is_ok do
-				buffer.append ","
-				append_json_entry(it, buffer)
-			end
-		end
-		it.finish
-		buffer.append "\}"
-	end
-
-	# Encode `self` in JSON.
-	#
-	#     var obj = new JsonObject
-	#     obj["foo"] = "bar"
-	#     assert obj.to_json == "\{\"foo\":\"bar\"\}"
-	#     obj = new JsonObject
-	#     obj["baz"] = null
-	#     assert obj.to_json == "\{\"baz\":null\}"
-	redef fun to_json do return to_json_by_append
-
-	redef fun pretty_json_visit(buffer, indent) do
-		buffer.append "\{\n"
-		indent += 1
-		var i = 0
-		for k, v in self do
-			buffer.append "\t" * indent
-			buffer.append "\"{k}\": "
-			if v isa JsonObject or v isa JsonArray then
-				v.pretty_json_visit(buffer, indent)
-			else
-				buffer.append v.to_json
-			end
-			if i < length - 1 then
-				buffer.append ","
-			end
-			buffer.append "\n"
-			i += 1
-		end
-		indent -= 1
-		buffer.append "\t" * indent
-		buffer.append "\}"
-	end
-
-	private fun append_json_entry(iterator: MapIterator[String, nullable Jsonable],
-			buffer: Buffer) do
-		buffer.append iterator.key.to_json
-		buffer.append ":"
-		buffer.append_json_of(iterator.item)
-		iterator.next
-	end
 end
 
 # A JSON Object.
@@ -370,51 +180,6 @@ end
 class JsonSequenceRead[E: nullable Jsonable]
 	super Jsonable
 	super SequenceRead[E]
-
-	redef fun append_json(buffer) do
-		buffer.append "["
-		var it = iterator
-		if it.is_ok then
-			append_json_entry(it, buffer)
-			while it.is_ok do
-				buffer.append ","
-				append_json_entry(it, buffer)
-			end
-		end
-		it.finish
-		buffer.append "]"
-	end
-
-	# Encode `self` in JSON.
-	#
-	#     var arr = new JsonArray.with_items("foo", null)
-	#     assert arr.to_json == "[\"foo\",null]"
-	#     arr.pop
-	#     assert arr.to_json =="[\"foo\"]"
-	#     arr.pop
-	#     assert arr.to_json =="[]"
-	redef fun to_json do return to_json_by_append
-
-	redef fun pretty_json_visit(buffer, indent) do
-		buffer.append "\["
-		var i = 0
-		for v in self do
-			if v isa JsonObject or v isa JsonArray then
-				v.pretty_json_visit(buffer, indent)
-			else
-				buffer.append v.to_json
-			end
-			if i < length - 1 then buffer.append ", "
-			i += 1
-		end
-		buffer.append "\]"
-	end
-
-	private fun append_json_entry(iterator: Iterator[nullable Jsonable],
-			buffer: Buffer) do
-		buffer.append_json_of(iterator.item)
-		iterator.next
-	end
 end
 
 # A JSON array.
@@ -425,48 +190,10 @@ end
 
 redef class JsonParseError
 	super Jsonable
-
-	# Get the JSON representation of `self`.
-	#
-	# ~~~
-	# var err = new JsonParseError("foo", new Position(1, 2, 3, 4, 5, 6))
-	# assert err.to_json == "\{\"error\":\"JsonParseError\"," +
-	#		"\"position\":\{" +
-	#			"\"pos_start\":1,\"pos_end\":2," +
-	#			"\"line_start\":3,\"line_end\":4," +
-	#			"\"col_start\":5,\"col_end\":6" +
-	#		"\},\"message\":\"foo\"\}"
-	# ~~~
-	redef fun to_json do
-		return "\{\"error\":\"JsonParseError\"," +
-				"\"position\":{position.to_json}," +
-				"\"message\":{message.to_json}\}"
-	end
-
-	redef fun pretty_json_visit(buf, indents) do
-		buf.clear
-		buf.append(to_json)
-	end
 end
 
 redef class Position
 	super Jsonable
-
-	# Get the JSON representation of `self`.
-	#
-	# ~~~
-	# var pos = new Position(1, 2, 3, 4, 5, 6)
-	# assert pos.to_json == "\{" +
-	#			"\"pos_start\":1,\"pos_end\":2," +
-	#			"\"line_start\":3,\"line_end\":4," +
-	#			"\"col_start\":5,\"col_end\":6" +
-	#		"\}"
-	# ~~~
-	redef fun to_json do
-		return "\{\"pos_start\":{pos_start},\"pos_end\":{pos_end}," +
-				"\"line_start\":{line_start},\"line_end\":{line_end}," +
-				"\"col_start\":{col_start},\"col_end\":{col_end}\}"
-	end
 end
 
 ################################################################################
diff --git a/lib/json/store.nit b/lib/json/store.nit
index 42a04df255..b8ce0f9a10 100644
--- a/lib/json/store.nit
+++ b/lib/json/store.nit
@@ -90,6 +90,7 @@
 module store
 
 import static
+import json
 
 # A JsonStore can save and load json data from file system.
 class JsonStore
diff --git a/lib/json/string_parser.nit b/lib/json/string_parser.nit
index 51d302e93e..19c8fd1fa3 100644
--- a/lib/json/string_parser.nit
+++ b/lib/json/string_parser.nit
@@ -344,21 +344,8 @@ redef class Text
 end
 
 redef class JsonParseError
+	serialize
 
 	# Location of the error in source
 	var location: nullable Location = null
-
-	# Get the JSON representation of `self`.
-	#
-	# ~~~
-	# var err = new JsonParseError("foo", new Position(1, 2, 3, 4, 5, 6))
-	# assert err.to_json == "Parsing error: foo"
-	# ~~~
-	redef fun to_json do
-		var l = location
-		var m = message
-		return if l == null then "Parsing error: {m}" else "Parsing error at {l}: {m}"
-	end
-
-	redef fun to_s do return to_json
 end
diff --git a/lib/linux/data_store.nit b/lib/linux/data_store.nit
index 4d7ff2bdeb..5924822b8c 100644
--- a/lib/linux/data_store.nit
+++ b/lib/linux/data_store.nit
@@ -20,7 +20,7 @@ module data_store
 import app::data_store
 private import xdg_basedir
 private import sqlite3
-private import json::serialization
+private import json
 
 redef class App
 	redef var data_store = new LinuxStore
diff --git a/lib/mongodb/mongodb.nit b/lib/mongodb/mongodb.nit
index 80c4d4c844..17b137fbf2 100644
--- a/lib/mongodb/mongodb.nit
+++ b/lib/mongodb/mongodb.nit
@@ -42,6 +42,7 @@
 # ~~~
 module mongodb
 
+import json::static
 import json
 private import native_mongodb
 
diff --git a/lib/mpi/mpi.nit b/lib/mpi/mpi.nit
index bc47997830..5ea6596db8 100644
--- a/lib/mpi/mpi.nit
+++ b/lib/mpi/mpi.nit
@@ -33,7 +33,7 @@ end
 import c
 intrude import core::text::flat
 import serialization
-private import json::serialization
+private import json
 
 in "C Header" `{
 	#include <mpi.h>
diff --git a/lib/neo4j/curl_json.nit b/lib/neo4j/curl_json.nit
index 03a7ca49bf..f2a541f565 100644
--- a/lib/neo4j/curl_json.nit
+++ b/lib/neo4j/curl_json.nit
@@ -16,6 +16,7 @@
 module curl_json
 
 import json::static
+import json
 intrude import curl
 
 # An abstract request that defines most of the standard options for Neo4j REST API
diff --git a/lib/neo4j/error.nit b/lib/neo4j/error.nit
index f9df000adf..58068ad7c7 100644
--- a/lib/neo4j/error.nit
+++ b/lib/neo4j/error.nit
@@ -12,23 +12,21 @@
 module neo4j::error
 
 import json::static
+import json
 
 # An error thrown by the `neo4j` API.
 #
 #     var error = new NeoError("ErrorMessage", "ErrorName")
-#     assert error.to_json == "\{\"error\":\"ErrorName\",\"message\":\"ErrorMessage\"\}"
+#     assert error.to_json == """{"message":"ErrorMessage","cause":null,"error":"ErrorName"}"""
 class NeoError
 	super Error
 	super Jsonable
+	serialize
 
 	# The name of the error.
 	#
 	# Used to programmatically distinguish this kind of error from others.
-	var name: String
-
-	redef fun to_json do
-		return "\{\"error\":{name.to_json},\"message\":{message.to_json}\}"
-	end
+	var name: String is serialize_as "error"
 
 	redef fun to_s do return "[{name}] {super}"
 end
diff --git a/lib/neo4j/graph/json_graph_store.nit b/lib/neo4j/graph/json_graph_store.nit
index 618a1d3485..d924bd9b41 100644
--- a/lib/neo4j/graph/json_graph_store.nit
+++ b/lib/neo4j/graph/json_graph_store.nit
@@ -191,35 +191,25 @@ redef class NeoGraph
 		end
 	end
 
-	redef fun to_json do return to_json_by_append
-
-	# Append the JSON representation of `self` to the specified buffer.
-	#
-	# For a description of the format, see `JsonGraphStore`.
-	#
-	# SEE: `to_json`
-	redef fun append_json(b) do
-		b.append "\{\"nodes\":["
-		append_entities_json(nodes, b)
-		b.append "],\"edges\":["
-		append_entities_json(edges, b)
-		b.append "]\}"
+	redef fun accept_json_serializer(v) do
+		v.stream.write "\{\"nodes\":["
+		append_entities_json(nodes, v)
+		v.stream.write "],\"edges\":["
+		append_entities_json(edges, v)
+		v.stream.write "]\}"
 	end
 
 	# Encode `self` in JSON.
 	#
 	# For a description of the format, see `JsonGraphStore`.
-	#
-	# SEE: `append_json`
-	private fun append_entities_json(entities: Collection[NeoEntity],
-			b: Buffer) do
+	private fun append_entities_json(entities: Collection[NeoEntity], v: JsonSerializer) do
 		var i = entities.iterator
 		if i.is_ok then
-			i.item.append_json_for(self, b)
+			i.item.append_json_for(self, v)
 			i.next
 			for entity in i do
-				b.add ','
-				entity.append_json_for(self, b)
+				v.stream.write ","
+				entity.append_json_for(self, v)
 			end
 		end
 	end
@@ -233,7 +223,7 @@ end
 redef class NeoEntity
 
 	# Append the JSON representation of the entity to the specified buffer.
-	fun append_json_for(graph: NeoGraph, buffer: Buffer) is abstract
+	fun append_json_for(graph: NeoGraph, v: JsonSerializer) is abstract
 end
 
 # Make `NeoNode` `Jsonable`.
@@ -273,32 +263,27 @@ redef class NeoNode
 		properties.add_all(json_properties)
 	end
 
-	redef fun to_json do return to_json_by_append
-
-	# Append the JSON representation of the node to the specified buffer.
-	#
-	# SEE: `JsonGraph`
-	redef fun append_json(b) do
-		b.append "\{\"labels\":["
+	redef fun accept_json_serializer(v) do
+		v.stream.write "\{\"labels\":["
 		var i = labels.iterator
 		if i.is_ok then
-			i.item.append_json(b)
+			i.item.serialize_to v
 			i.next
 			for lab in i do
-				b.add ','
-				lab.append_json(b)
+				v.stream.write ","
+				lab.serialize_to v
 			end
 		end
-		b.append "],\"properties\":"
-		properties.append_json(b)
-		b.add '}'
+		v.stream.write "],\"properties\":"
+		properties.serialize_to v
+		v.stream.write "}"
 	end
 
 	redef fun to_s do return to_json
 
 	# Append the JSON representation of the node to the specified buffer.
-	redef fun append_json_for(graph, buffer) do
-		append_json(buffer)
+	redef fun append_json_for(graph, v) do
+		accept_json_serializer v
 	end
 end
 
@@ -307,15 +292,15 @@ redef class NeoEdge
 	# Append the JSON representation of the relationship to the specified buffer.
 	#
 	# Use the IDs specfied by `graph.nodes`.
-	redef fun append_json_for(graph, buffer) do
-		buffer.append "\{\"type\":"
-		rel_type.as(not null).append_json(buffer)
-		buffer.append ",\"properties\":"
-		properties.append_json(buffer)
-		buffer.append ",\"from\":"
-		graph.nodes.id_of(from).append_json(buffer)
-		buffer.append ",\"to\":"
-		graph.nodes.id_of(to).append_json(buffer)
-		buffer.append "}"
+	redef fun append_json_for(graph, v) do
+		v.stream.write "\{\"type\":"
+		rel_type.as(not null).serialize_to(v)
+		v.stream.write ",\"properties\":"
+		properties.serialize_to(v)
+		v.stream.write ",\"from\":"
+		graph.nodes.id_of(from).serialize_to(v)
+		v.stream.write ",\"to\":"
+		graph.nodes.id_of(to).serialize_to(v)
+		v.stream.write "}"
 	end
 end
diff --git a/lib/nitcc_runtime.nit b/lib/nitcc_runtime.nit
index a09bc3cbde..cfddec3f65 100644
--- a/lib/nitcc_runtime.nit
+++ b/lib/nitcc_runtime.nit
@@ -15,6 +15,8 @@
 # Runtime library required by parsers and lexers generated by nitcc
 module nitcc_runtime
 
+import serialization
+
 # A abstract parser engine generated by nitcc
 abstract class Parser
 	# The list of tokens
@@ -303,6 +305,8 @@ end
 # A position into a input stream
 # Used to give position to tokens
 class Position
+	serialize
+
 	var pos_start: Int
 	var pos_end: Int
 	var line_start: Int
diff --git a/lib/nitcorn/restful.nit b/lib/nitcorn/restful.nit
index 158643a281..4342a111b7 100644
--- a/lib/nitcorn/restful.nit
+++ b/lib/nitcorn/restful.nit
@@ -16,7 +16,7 @@
 module restful is new_annotation(restful)
 
 import nitcorn
-import json::serialization
+import json
 
 # Action with `restful` methods
 class RestfulAction
diff --git a/lib/parser_base.nit b/lib/parser_base.nit
index f97fbf0a7f..b62313763b 100644
--- a/lib/parser_base.nit
+++ b/lib/parser_base.nit
@@ -11,6 +11,8 @@
 # Simple base for hand-made parsers of all kinds
 module parser_base
 
+import serialization
+
 # Basic facilities for common parser operations on String sources
 class StringProcessor
 	# Source document to parse
@@ -114,6 +116,8 @@ end
 
 # Information about the location of an entity in a source document
 class Location
+	serialize
+
 	# Line in which the element is described
 	var line: Int
 	# Offset in the line at which the element is positioned
diff --git a/lib/popcorn/pop_handlers.nit b/lib/popcorn/pop_handlers.nit
index e4da4a5428..8d66cc9580 100644
--- a/lib/popcorn/pop_handlers.nit
+++ b/lib/popcorn/pop_handlers.nit
@@ -18,6 +18,7 @@
 module pop_handlers
 
 import pop_routes
+import json::static
 import json
 
 # Class handler for a route.
diff --git a/lib/popcorn/pop_repos.nit b/lib/popcorn/pop_repos.nit
index 4c3ea14c7a..7b02c3511c 100644
--- a/lib/popcorn/pop_repos.nit
+++ b/lib/popcorn/pop_repos.nit
@@ -54,7 +54,6 @@
 #	redef fun to_s do return title
 #	redef fun ==(o) do return o isa SELF and id == o.id
 #	redef fun hash do return id.hash
-#	redef fun to_json do return serialize_to_json
 # end
 #
 # # We then need to subclass the `MongoRepository` to provide Book specific services.
@@ -121,7 +120,7 @@ module pop_repos
 
 import popcorn::pop_config
 import serialization
-import json::serialization
+import json
 import mongodb::queries
 
 redef class AppConfig
@@ -436,7 +435,6 @@ abstract class RepoObject
 
 	redef fun hash do return id.hash
 	redef fun to_s do return id
-	redef fun to_json do return serialize_to_json
 end
 
 # JsonObject can be used as a `RepositoryQuery`.
diff --git a/lib/popcorn/pop_validation.nit b/lib/popcorn/pop_validation.nit
index 386bb24ff8..b1464b857a 100644
--- a/lib/popcorn/pop_validation.nit
+++ b/lib/popcorn/pop_validation.nit
@@ -70,7 +70,7 @@
 # ~~~
 module pop_validation
 
-import json
+import json::static
 
 # The base class of all validators
 abstract class DocumentValidator
@@ -152,7 +152,7 @@ class ValidationResult
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 
 	# Returns the validation result as a pretty formated string
 	fun to_pretty_string: String do
diff --git a/lib/serialization/README.md b/lib/serialization/README.md
index 47eef73b7a..3f6ac6c063 100644
--- a/lib/serialization/README.md
+++ b/lib/serialization/README.md
@@ -234,7 +234,7 @@ The main implementations of these services are `JsonSerializer` and `JsonDeseria
 from the `json_serialization` module.
 
 ~~~
-import json_serialization
+import json
 import user_credentials
 
 # Data to be serialized and deserialized
diff --git a/src/doc/doc_phases/doc_indexing.nit b/src/doc/doc_phases/doc_indexing.nit
index d532d9c9e8..066f8ab73a 100644
--- a/src/doc/doc_phases/doc_indexing.nit
+++ b/src/doc/doc_phases/doc_indexing.nit
@@ -18,6 +18,7 @@ module doc_indexing
 import doc_base
 import html_templates::html_model # FIXME maybe this phase should depend on `html_render`
 private import json::static
+private import json
 
 # Generate the index for then Nitdoc QuickSearch field.
 #
@@ -67,7 +68,7 @@ class IndexingPhase
 		var buffer = new Buffer
 		tpl.add buffer
 		buffer.append "var nitdocQuickSearchRawList="
-		table.append_json buffer
+		buffer.append table.to_json
 		buffer.append ";"
 		return tpl
 	end
@@ -95,14 +96,11 @@ end
 # A QuickSearch result.
 private class QuickSearchResult
 	super Jsonable
+	serialize
 
 	# The text of the link.
 	var txt: String
 
 	# The destination of the link.
 	var url: String
-
-	redef fun to_json do
-		return "\{\"txt\":{txt.to_json},\"url\":{url.to_json}\}"
-	end
 end
diff --git a/src/doc/html_templates/html_components.nit b/src/doc/html_templates/html_components.nit
index 630d28eb11..a0f13993a6 100644
--- a/src/doc/html_templates/html_components.nit
+++ b/src/doc/html_templates/html_components.nit
@@ -18,7 +18,7 @@ module html_components
 
 import doc_base
 import html::bootstrap
-import json::static
+import json
 
 # A label with a text content.
 class DocHTMLLabel
diff --git a/src/examples/nitwebcrawl.nit b/src/examples/nitwebcrawl.nit
index 1187476d75..e981ac6f1e 100644
--- a/src/examples/nitwebcrawl.nit
+++ b/src/examples/nitwebcrawl.nit
@@ -15,7 +15,7 @@
 # Crawler on the nitweb web API
 module nitwebcrawl
 
-import json
+import json::static
 
 # Download a HTTP resource
 fun curl(url: String): String do
diff --git a/src/model/model_json.nit b/src/model/model_json.nit
index 2c5cd04395..1d8483cd7a 100644
--- a/src/model/model_json.nit
+++ b/src/model/model_json.nit
@@ -25,6 +25,7 @@
 module model_json
 
 import model::model_collect
+import json::static
 import json
 import loader
 
@@ -68,7 +69,7 @@ redef class MEntity
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 
 	# Return `self` as a JsonObject with references.
 	#
@@ -95,7 +96,7 @@ redef class MDoc
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 redef class Location
@@ -115,13 +116,13 @@ redef class Location
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 redef class MVisibility
 	super Jsonable
 
-	redef fun to_json do return to_s.to_json
+	redef fun serialize_to(v) do to_s.serialize_to(v)
 end
 
 redef class MPackage
diff --git a/src/web/api_catalog.nit b/src/web/api_catalog.nit
index 30b8757182..bd403adb61 100644
--- a/src/web/api_catalog.nit
+++ b/src/web/api_catalog.nit
@@ -137,12 +137,10 @@ end
 redef class Person
 	super Jsonable
 
-	redef fun to_json do
-		var obj = new JsonObject
-		obj["name"] = name
-		obj["email"] = email
-		obj["page"] = page
-		obj["hash"] = (email or else "").md5.to_lower
-		return obj.to_json
+	redef fun core_serialize_to(v) do
+		v.serialize_attribute("name", name)
+		v.serialize_attribute("email", email)
+		v.serialize_attribute("page", page)
+		v.serialize_attribute("hash", (email or else "").md5.to_lower)
 	end
 end
diff --git a/src/web/api_feedback.nit b/src/web/api_feedback.nit
index e2bfa9a014..a5cacff6fa 100644
--- a/src/web/api_feedback.nit
+++ b/src/web/api_feedback.nit
@@ -100,7 +100,7 @@ class MEntityRatings
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 # Rating value of a MEntity
@@ -130,5 +130,5 @@ class MEntityRating
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
diff --git a/src/web/api_metrics.nit b/src/web/api_metrics.nit
index bb0147c180..8c01c0dfb9 100644
--- a/src/web/api_metrics.nit
+++ b/src/web/api_metrics.nit
@@ -162,7 +162,7 @@ redef class MetricSet
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 redef class Metric
@@ -179,7 +179,7 @@ redef class Metric
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 redef class IntMetric
diff --git a/src/web/web_base.nit b/src/web/web_base.nit
index 14bfcca693..60f7f2b5a1 100644
--- a/src/web/web_base.nit
+++ b/src/web/web_base.nit
@@ -124,7 +124,7 @@ class APIError
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
 
 # Fullname representation that can be used to build decorated links
@@ -134,9 +134,10 @@ end
 class Namespace
 	super Array[nullable NSEntity]
 	super NSEntity
+	serialize
 
 	redef fun to_s do return self.join("")
-	redef fun to_json do return (new JsonArray.from(self)).to_json
+	redef fun serialize_to(v) do to_a.serialize_to(v)
 end
 
 # Something that goes in a Namespace
@@ -154,16 +155,17 @@ end
 # an infinite loop.
 class NSRef
 	super NSEntity
+	serialize
 
 	# The mentity to link to/
 	var mentity: MEntity
 
-	redef fun to_json do
+	redef fun serialize_to(v) do
 		var obj = new JsonObject
 		obj["web_url"] = mentity.web_url
 		obj["api_url"] = mentity.api_url
 		obj["name"] = mentity.name
-		return obj.to_json
+		obj.serialize_to(v)
 	end
 end
 
@@ -364,5 +366,5 @@ redef class POSetElement[E]
 		return obj
 	end
 
-	redef fun to_json do return json.to_json
+	redef fun serialize_to(v) do json.serialize_to(v)
 end
diff --git a/tests/sav/json_output.res b/tests/sav/json_output.res
index 4162e8d981..80f6c94a9f 100644
--- a/tests/sav/json_output.res
+++ b/tests/sav/json_output.res
@@ -7,4 +7,3 @@ JsonArray
 	"blue": [1, 2],
 	"ocean": ["fishy", "salty"]
 }
-
diff --git a/tests/sav/neo_doxygen_descriptions.res b/tests/sav/neo_doxygen_descriptions.res
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/tests/sav/neo_doxygen_member_resolve_introducer.res b/tests/sav/neo_doxygen_member_resolve_introducer.res
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/tests/sav/nitce/test_json_deserialization_alt1.res b/tests/sav/nitce/test_json_deserialization_alt1.res
index cb74989ec4..d757542186 100644
--- a/tests/sav/nitce/test_json_deserialization_alt1.res
+++ b/tests/sav/nitce/test_json_deserialization_alt1.res
@@ -2,7 +2,7 @@
 <A: true a 0.123 1234 asdf false p4ssw0rd>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null}
 
 # Back in Nit:
 <A: true a 0.123 1234 asdf false p4ssw0rd>
@@ -11,7 +11,7 @@
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"}
 
 # Back in Nit:
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
@@ -20,7 +20,7 @@
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null},"b": {"__kind": "obj", "__id": 2, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null},"b":{"__kind": "obj", "__id": 2, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Back in Nit:
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
@@ -30,7 +30,7 @@
 <- false p4ssw0rd> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "new line ->\n<-","n": null,"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"new line ->\n<-","n":null,"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
 # Back in Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
@@ -40,7 +40,7 @@
 <E: a: hello, 1234, 123.4; b: hella, 2345, 234.5>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "E","a": {"__kind": "obj", "__id": 1, "__class": "Array","__items": ["hello",1234,123.4]},"b": {"__kind": "obj", "__id": 2, "__class": "Array","__items": ["hella",2345,234.5]}}
+{"__kind": "obj", "__id": 0, "__class": "E","a":{"__kind": "obj", "__id": 1, "__class": "Array","__items": ["hello",1234,123.4]},"b":{"__kind": "obj", "__id": 2, "__class": "Array","__items": ["hella",2345,234.5]}}
 
 # Back in Nit:
 <E: a: hello, 1234, 123.4; b: hella, 2345, 234.5>
@@ -53,7 +53,7 @@ Deserialization Error: Wrong type on `E::b` expected `Array[nullable Serializabl
 <E: 2222>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "F","n": 2222}
+{"__kind": "obj", "__id": 0, "__class": "F","n":2222}
 
 # Back in Nit:
 null
@@ -63,7 +63,7 @@ Deserialization Error: Doesn't know how to deserialize class "F"
 <E: 33.33>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "F","n": 33.33}
+{"__kind": "obj", "__id": 0, "__class": "F","n":33.33}
 
 # Back in Nit:
 null
@@ -73,7 +73,7 @@ Deserialization Error: Doesn't know how to deserialize class "F"
 <G: hs: -1, 0; s: one, two; hm: one. 1, two. 2; am: three. 3, four. 4>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "G","hs": {"__kind": "obj", "__id": 1, "__class": "HashSet","__items": [-1,0]},"s": {"__kind": "obj", "__id": 2, "__class": "ArraySet","__items": ["one","two"]},"hm": {"__kind": "obj", "__id": 3, "__class": "HashMap", "__length": 2,"__keys": ["one","two"],"__values": [1,2]},"am": {"__kind": "obj", "__id": 4, "__class": "ArrayMap", "__length": 2,"__keys": ["three","four"],"__values": ["3","4"]}}
+{"__kind": "obj", "__id": 0, "__class": "G","hs":{"__kind": "obj", "__id": 1, "__class": "HashSet","__items": [-1,0]},"s":{"__kind": "obj", "__id": 2, "__class": "ArraySet","__items": ["one","two"]},"hm":{"__kind": "obj", "__id": 3, "__class": "HashMap", "__length": 2,"__keys": ["one","two"],"__values": [1,2]},"am":{"__kind": "obj", "__id": 4, "__class": "ArrayMap", "__length": 2,"__keys": ["three","four"],"__values": ["3","4"]}}
 
 # Back in Nit:
 <G: hs: ; s: ; hm: ; am: >
diff --git a/tests/sav/nitce/test_json_deserialization_alt3.res b/tests/sav/nitce/test_json_deserialization_alt3.res
index 3a3aec0959..a6238372d1 100644
--- a/tests/sav/nitce/test_json_deserialization_alt3.res
+++ b/tests/sav/nitce/test_json_deserialization_alt3.res
@@ -100,19 +100,11 @@
 	"__kind": "obj", "__id": 0, "__class": "E",
 	"a": {
 		"__kind": "obj", "__id": 1, "__class": "Array",
-		"__items": [
-			"hello",
-			1234,
-			123.4
-		]
+		"__items": ["hello", 1234, 123.4]
 	},
 	"b": {
 		"__kind": "obj", "__id": 2, "__class": "Array",
-		"__items": [
-			"hella",
-			2345,
-			234.5
-		]
+		"__items": ["hella", 2345, 234.5]
 	}
 }
 
@@ -157,39 +149,21 @@ Deserialization Error: Doesn't know how to deserialize class "F"
 	"__kind": "obj", "__id": 0, "__class": "G",
 	"hs": {
 		"__kind": "obj", "__id": 1, "__class": "HashSet",
-		"__items": [
-			-1,
-			0
-		]
+		"__items": [-1, 0]
 	},
 	"s": {
 		"__kind": "obj", "__id": 2, "__class": "ArraySet",
-		"__items": [
-			"one",
-			"two"
-		]
+		"__items": ["one", "two"]
 	},
 	"hm": {
 		"__kind": "obj", "__id": 3, "__class": "HashMap", "__length": 2,
-		"__keys": [
-			"one",
-			"two"
-		],
-		"__values": [
-			1,
-			2
-		]
+		"__keys": ["one", "two"],
+		"__values": [1, 2]
 	},
 	"am": {
 		"__kind": "obj", "__id": 4, "__class": "ArrayMap", "__length": 2,
-		"__keys": [
-			"three",
-			"four"
-		],
-		"__values": [
-			"3",
-			"4"
-		]
+		"__keys": ["three", "four"],
+		"__values": ["3", "4"]
 	}
 }
 
diff --git a/tests/sav/nitce/test_serialization.res b/tests/sav/nitce/test_serialization.res
index 67a1674925..cc516c58ea 100644
--- a/tests/sav/nitce/test_serialization.res
+++ b/tests/sav/nitce/test_serialization.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_alt2.res b/tests/sav/nitce/test_serialization_alt2.res
index d3fb349ebf..28727b4c1f 100644
--- a/tests/sav/nitce/test_serialization_alt2.res
+++ b/tests/sav/nitce/test_serialization_alt2.res
@@ -5,24 +5,24 @@ alt/test_serialization_alt2.nit:64,1--72,3: Warning: superfluous use of `auto_se
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]}},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]}},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_alt3.res b/tests/sav/nitce/test_serialization_alt3.res
index 3b72eda387..01b101ed13 100644
--- a/tests/sav/nitce/test_serialization_alt3.res
+++ b/tests/sav/nitce/test_serialization_alt3.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt3.nit:40,1--51,3: Warning: superfluous use of `noseria
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]}},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]}},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_alt4.res b/tests/sav/nitce/test_serialization_alt4.res
index 5f408342fa..a45b63ed2d 100644
--- a/tests/sav/nitce/test_serialization_alt4.res
+++ b/tests/sav/nitce/test_serialization_alt4.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt4.nit:29,2--31,26: Warning: superfluous use of `serial
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_alt5.res b/tests/sav/nitce/test_serialization_alt5.res
index cc170878d9..d5d2e2c790 100644
--- a/tests/sav/nitce/test_serialization_alt5.res
+++ b/tests/sav/nitce/test_serialization_alt5.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt5.nit:22,1--38,3: Warning: duplicated annotation `seri
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_redef.res b/tests/sav/nitce/test_serialization_redef.res
index 67a1674925..cc516c58ea 100644
--- a/tests/sav/nitce/test_serialization_redef.res
+++ b/tests/sav/nitce/test_serialization_redef.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_redef_alt0.res b/tests/sav/nitce/test_serialization_redef_alt0.res
index a6a77fddd1..c0589ed0ce 100644
--- a/tests/sav/nitce/test_serialization_redef_alt0.res
+++ b/tests/sav/nitce/test_serialization_redef_alt0.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef"}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef"},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_redef_alt1.res b/tests/sav/nitce/test_serialization_redef_alt1.res
index ec4a7d9fd5..7c65b3dced 100644
--- a/tests/sav/nitce/test_serialization_redef_alt1.res
+++ b/tests/sav/nitce/test_serialization_redef_alt1.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","ffff": 6.789,"bbbb": false,"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","ffff":6.789,"bbbb":false,"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/nitce/test_serialization_redef_alt2.res b/tests/sav/nitce/test_serialization_redef_alt2.res
index 48b21cc2b1..e6c3c90d99 100644
--- a/tests/sav/nitce/test_serialization_redef_alt2.res
+++ b/tests/sav/nitce/test_serialization_redef_alt2.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef"}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef"},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "\tf\"\r\\/","ffff": 6.789,"bbbb": false,"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"\tf\"\r\\/","ffff":6.789,"bbbb":false,"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_adhoc_json_parse_args1.res b/tests/sav/test_adhoc_json_parse_args1.res
index 2e9d00b8ca..aa4f276f6a 100644
--- a/tests/sav/test_adhoc_json_parse_args1.res
+++ b/tests/sav/test_adhoc_json_parse_args1.res
@@ -17,4 +17,3 @@
 	"Zip": "94085",
 	"Country": "US"
 }]
-
diff --git a/tests/sav/test_json_deserialization.res b/tests/sav/test_json_deserialization.res
index 5ab004a8e9..c4040be9dc 100644
--- a/tests/sav/test_json_deserialization.res
+++ b/tests/sav/test_json_deserialization.res
@@ -2,7 +2,7 @@
 <A: true a 0.123 1234 asdf false p4ssw0rd>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null}
 
 # Back in Nit:
 <A: true a 0.123 1234 asdf false p4ssw0rd>
@@ -11,7 +11,7 @@
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"}
 
 # Back in Nit:
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
@@ -20,7 +20,7 @@
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null},"b": {"__kind": "obj", "__id": 2, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null},"b":{"__kind": "obj", "__id": 2, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Back in Nit:
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
@@ -30,7 +30,7 @@
 <- false p4ssw0rd> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "new line ->\n<-","n": null,"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"new line ->\n<-","n":null,"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
 # Back in Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
diff --git a/tests/sav/test_json_deserialization_alt1.res b/tests/sav/test_json_deserialization_alt1.res
index 161fb58c57..91b7df1cfd 100644
--- a/tests/sav/test_json_deserialization_alt1.res
+++ b/tests/sav/test_json_deserialization_alt1.res
@@ -2,7 +2,7 @@
 <A: true a 0.123 1234 asdf false p4ssw0rd>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null}
 
 # Back in Nit:
 <A: true a 0.123 1234 asdf false p4ssw0rd>
@@ -11,7 +11,7 @@
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"}
 
 # Back in Nit:
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
@@ -20,7 +20,7 @@
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null},"b": {"__kind": "obj", "__id": 2, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null},"b":{"__kind": "obj", "__id": 2, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Back in Nit:
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
@@ -30,7 +30,7 @@
 <- false p4ssw0rd> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"serialization_specific_name": "new line ->\n<-","n": null,"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"serialization_specific_name":"new line ->\n<-","n":null,"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
 # Back in Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
@@ -40,7 +40,7 @@
 <E: a: hello, 1234, 123.4; b: hella, 2345, 234.5>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "E","a": {"__kind": "obj", "__id": 1, "__class": "Array[Object]","__items": ["hello",1234,123.4]},"b": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Serializable]","__items": ["hella",2345,234.5]}}
+{"__kind": "obj", "__id": 0, "__class": "E","a":{"__kind": "obj", "__id": 1, "__class": "Array[Object]","__items": ["hello",1234,123.4]},"b":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Serializable]","__items": ["hella",2345,234.5]}}
 
 # Back in Nit:
 <E: a: hello, 1234, 123.4; b: hella, 2345, 234.5>
@@ -49,7 +49,7 @@
 <E: 2222>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "F[Int]","n": 2222}
+{"__kind": "obj", "__id": 0, "__class": "F[Int]","n":2222}
 
 # Back in Nit:
 <E: 2222>
@@ -58,7 +58,7 @@
 <E: 33.33>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "F[Float]","n": 33.33}
+{"__kind": "obj", "__id": 0, "__class": "F[Float]","n":33.33}
 
 # Back in Nit:
 <E: 33.33>
@@ -67,7 +67,7 @@
 <G: hs: -1, 0; s: one, two; hm: one. 1, two. 2; am: three. 3, four. 4>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "G","hs": {"__kind": "obj", "__id": 1, "__class": "HashSet[Int]","__items": [-1,0]},"s": {"__kind": "obj", "__id": 2, "__class": "ArraySet[String]","__items": ["one","two"]},"hm": {"__kind": "obj", "__id": 3, "__class": "HashMap[String, Int]", "__length": 2,"__keys": ["one","two"],"__values": [1,2]},"am": {"__kind": "obj", "__id": 4, "__class": "ArrayMap[String, String]", "__length": 2,"__keys": ["three","four"],"__values": ["3","4"]}}
+{"__kind": "obj", "__id": 0, "__class": "G","hs":{"__kind": "obj", "__id": 1, "__class": "HashSet[Int]","__items": [-1,0]},"s":{"__kind": "obj", "__id": 2, "__class": "ArraySet[String]","__items": ["one","two"]},"hm":{"__kind": "obj", "__id": 3, "__class": "HashMap[String, Int]", "__length": 2,"__keys": ["one","two"],"__values": [1,2]},"am":{"__kind": "obj", "__id": 4, "__class": "ArrayMap[String, String]", "__length": 2,"__keys": ["three","four"],"__values": ["3","4"]}}
 
 # Back in Nit:
 <G: hs: -1, 0; s: one, two; hm: one. 1, two. 2; am: three. 3, four. 4>
diff --git a/tests/sav/test_json_deserialization_alt2.res b/tests/sav/test_json_deserialization_alt2.res
index 48005ec114..f7aaf3181d 100644
--- a/tests/sav/test_json_deserialization_alt2.res
+++ b/tests/sav/test_json_deserialization_alt2.res
@@ -2,19 +2,19 @@
 <A: true a 0.123 1234 asdf false p4ssw0rd>
 
 # Json:
-{"b": true,"c": "a","f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null}
+{"b":true,"c":"a","f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>
 
 # Json:
-{"b": false,"c": "b","f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"}
+{"b":false,"c":"b","f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false p4ssw0rd> <B: <A: false b 123.123 2345 hjkl true p4ssw0rd> 1111 qwer>>
 
 # Json:
-{"a": {"b": true,"c": "a","f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null},"b": {"b": false,"c": "b","f": 123.123,"i": 2345,"serialization_specific_name": "hjkl","n": 12,"ii": 1111,"ss": "qwer"},"aa": {"b": true,"c": "a","f": 0.123,"i": 1234,"serialization_specific_name": "asdf","n": null}}
+{"a":{"b":true,"c":"a","f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null},"b":{"b":false,"c":"b","f":123.123,"i":2345,"serialization_specific_name":"hjkl","n":12,"ii":1111,"ss":"qwer"},"aa":{"b":true,"c":"a","f":0.123,"i":1234,"serialization_specific_name":"asdf","n":null}}
 
 Serialization warning: Cycle detected in serialized object, replacing reference with 'null'.
 # Nit:
@@ -22,29 +22,29 @@ Serialization warning: Cycle detected in serialized object, replacing reference
 <- false p4ssw0rd> 1111 	f"
\/> true>
 
 # Json:
-{"b": false,"c": "b","f": 123.123,"i": 2345,"serialization_specific_name": "new line ->\n<-","n": null,"ii": 1111,"ss": "\tf\"\r\\/","d": null}
+{"b":false,"c":"b","f":123.123,"i":2345,"serialization_specific_name":"new line ->\n<-","n":null,"ii":1111,"ss":"\tf\"\r\\/","d":null}
 
 # Nit:
 <E: a: hello, 1234, 123.4; b: hella, 2345, 234.5>
 
 # Json:
-{"a": ["hello",1234,123.4],"b": ["hella",2345,234.5]}
+{"a":["hello",1234,123.4],"b":["hella",2345,234.5]}
 
 # Nit:
 <E: 2222>
 
 # Json:
-{"n": 2222}
+{"n":2222}
 
 # Nit:
 <E: 33.33>
 
 # Json:
-{"n": 33.33}
+{"n":33.33}
 
 # Nit:
 <G: hs: -1, 0; s: one, two; hm: one. 1, two. 2; am: three. 3, four. 4>
 
 # Json:
-{"hs": [-1,0],"s": ["one","two"],"hm": {"one": 1,"two": 2},"am": {"three": "3","four": "4"}}
+{"hs":[-1,0],"s":["one","two"],"hm":{"one":1,"two":2},"am":{"three":"3","four":"4"}}
 
diff --git a/tests/sav/test_json_deserialization_alt3.res b/tests/sav/test_json_deserialization_alt3.res
index 3904578841..d58b2de909 100644
--- a/tests/sav/test_json_deserialization_alt3.res
+++ b/tests/sav/test_json_deserialization_alt3.res
@@ -100,19 +100,11 @@
 	"__kind": "obj", "__id": 0, "__class": "E",
 	"a": {
 		"__kind": "obj", "__id": 1, "__class": "Array[Object]",
-		"__items": [
-			"hello",
-			1234,
-			123.4
-		]
+		"__items": ["hello", 1234, 123.4]
 	},
 	"b": {
 		"__kind": "obj", "__id": 2, "__class": "Array[nullable Serializable]",
-		"__items": [
-			"hella",
-			2345,
-			234.5
-		]
+		"__items": ["hella", 2345, 234.5]
 	}
 }
 
@@ -151,39 +143,21 @@
 	"__kind": "obj", "__id": 0, "__class": "G",
 	"hs": {
 		"__kind": "obj", "__id": 1, "__class": "HashSet[Int]",
-		"__items": [
-			-1,
-			0
-		]
+		"__items": [-1, 0]
 	},
 	"s": {
 		"__kind": "obj", "__id": 2, "__class": "ArraySet[String]",
-		"__items": [
-			"one",
-			"two"
-		]
+		"__items": ["one", "two"]
 	},
 	"hm": {
 		"__kind": "obj", "__id": 3, "__class": "HashMap[String, Int]", "__length": 2,
-		"__keys": [
-			"one",
-			"two"
-		],
-		"__values": [
-			1,
-			2
-		]
+		"__keys": ["one", "two"],
+		"__values": [1, 2]
 	},
 	"am": {
 		"__kind": "obj", "__id": 4, "__class": "ArrayMap[String, String]", "__length": 2,
-		"__keys": [
-			"three",
-			"four"
-		],
-		"__values": [
-			"3",
-			"4"
-		]
+		"__keys": ["three", "four"],
+		"__values": ["3", "4"]
 	}
 }
 
diff --git a/tests/sav/test_json_deserialization_alt4.res b/tests/sav/test_json_deserialization_alt4.res
index 5527174df0..3c56592329 100644
--- a/tests/sav/test_json_deserialization_alt4.res
+++ b/tests/sav/test_json_deserialization_alt4.res
@@ -82,16 +82,8 @@ Serialization warning: Cycle detected in serialized object, replacing reference
 
 # Json:
 {
-	"a": [
-		"hello",
-		1234,
-		123.4
-	],
-	"b": [
-		"hella",
-		2345,
-		234.5
-	]
+	"a": ["hello", 1234, 123.4],
+	"b": ["hella", 2345, 234.5]
 }
 
 # Nit:
@@ -115,14 +107,8 @@ Serialization warning: Cycle detected in serialized object, replacing reference
 
 # Json:
 {
-	"hs": [
-		-1,
-		0
-	],
-	"s": [
-		"one",
-		"two"
-	],
+	"hs": [-1, 0],
+	"s": ["one", "two"],
 	"hm": {
 		"one": 1,
 		"two": 2
diff --git a/tests/sav/test_json_deserialization_plain.res b/tests/sav/test_json_deserialization_plain.res
index 62b3c82090..c8b7dd2eef 100644
--- a/tests/sav/test_json_deserialization_plain.res
+++ b/tests/sav/test_json_deserialization_plain.res
@@ -26,6 +26,6 @@
 # Nit: <MyClass i:123 s:hello f:123.456 a:[one, two] o:<null>>
 
 # JSON: not valid json
-# Errors: 'Parsing error at line 1, position 1: Error: bad JSON entity'
+# Errors: 'Error: bad JSON entity'
 # Nit: null
 
diff --git a/tests/sav/test_json_unicode.res b/tests/sav/test_json_unicode.res
index c0f61ccdcb..9a44a7c843 100644
--- a/tests/sav/test_json_unicode.res
+++ b/tests/sav/test_json_unicode.res
@@ -2,4 +2,3 @@
 	"beer": "test",
 	"name": "Gaëa"
 }
-
diff --git a/tests/sav/test_serialization.res b/tests/sav/test_serialization.res
index e3b56a7868..8480abe0cd 100644
--- a/tests/sav/test_serialization.res
+++ b/tests/sav/test_serialization.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_alt1.res b/tests/sav/test_serialization_alt1.res
index f275932a14..f640ce7afc 100644
--- a/tests/sav/test_serialization_alt1.res
+++ b/tests/sav/test_serialization_alt1.res
@@ -2,19 +2,19 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"b": true,"c": "a","f": 0.123,"i": 1234,"s": "asdf","n": null,"array": [88,"hello",null]}
+{"b":true,"c":"a","f":0.123,"i":1234,"s":"asdf","n":null,"array":[88,"hello",null]}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"b": false,"c": "b","f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": [88,"hello",null],"ii": 1111,"ss": "qwer"}
+{"b":false,"c":"b","f":123.123,"i":2345,"s":"hjkl","n":12,"array":[88,"hello",null],"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"a": {"b": true,"c": "a","f": 0.123,"i": 1234,"s": "asdf","n": null,"array": [88,"hello",null]},"b": {"b": false,"c": "b","f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": [88,"hello",null],"ii": 1111,"ss": "qwer"},"aa": {"b": true,"c": "a","f": 0.123,"i": 1234,"s": "asdf","n": null,"array": [88,"hello",null]}}
+{"a":{"b":true,"c":"a","f":0.123,"i":1234,"s":"asdf","n":null,"array":[88,"hello",null]},"b":{"b":false,"c":"b","f":123.123,"i":2345,"s":"hjkl","n":12,"array":[88,"hello",null],"ii":1111,"ss":"qwer"},"aa":{"b":true,"c":"a","f":0.123,"i":1234,"s":"asdf","n":null,"array":[88,"hello",null]}}
 
 Serialization warning: Cycle detected in serialized object, replacing reference with 'null'.
 # Nit:
@@ -22,5 +22,5 @@ Serialization warning: Cycle detected in serialized object, replacing reference
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"b": false,"c": "b","f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": [88,"hello",null],"ii": 1111,"ss": "\tf\"\r\\/","d": null}
+{"b":false,"c":"b","f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":[88,"hello",null],"ii":1111,"ss":"\tf\"\r\\/","d":null}
 
diff --git a/tests/sav/test_serialization_alt2.res b/tests/sav/test_serialization_alt2.res
index 42ad47b0ac..e733f605cd 100644
--- a/tests/sav/test_serialization_alt2.res
+++ b/tests/sav/test_serialization_alt2.res
@@ -5,24 +5,24 @@ alt/test_serialization_alt2.nit:64,1--72,3: Warning: superfluous use of `auto_se
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_alt3.res b/tests/sav/test_serialization_alt3.res
index 9ad407314d..8818e8fe99 100644
--- a/tests/sav/test_serialization_alt3.res
+++ b/tests/sav/test_serialization_alt3.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt3.nit:40,1--51,3: Warning: superfluous use of `noseria
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_alt4.res b/tests/sav/test_serialization_alt4.res
index 039170f672..06e2015671 100644
--- a/tests/sav/test_serialization_alt4.res
+++ b/tests/sav/test_serialization_alt4.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt4.nit:29,2--31,26: Warning: superfluous use of `serial
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_alt5.res b/tests/sav/test_serialization_alt5.res
index 6f763c2682..3c56b96851 100644
--- a/tests/sav/test_serialization_alt5.res
+++ b/tests/sav/test_serialization_alt5.res
@@ -3,24 +3,24 @@ alt/test_serialization_alt5.nit:22,1--38,3: Warning: duplicated annotation `seri
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_redef.res b/tests/sav/test_serialization_redef.res
index e3b56a7868..8480abe0cd 100644
--- a/tests/sav/test_serialization_redef.res
+++ b/tests/sav/test_serialization_redef.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_redef_alt0.res b/tests/sav/test_serialization_redef_alt0.res
index 337cdaa9a2..9eab831a65 100644
--- a/tests/sav/test_serialization_redef_alt0.res
+++ b/tests/sav/test_serialization_redef_alt0.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef"}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer"}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer"}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer"},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef"},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer"},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "\tf\"\r\\/","d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"\tf\"\r\\/","d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_redef_alt1.res b/tests/sav/test_serialization_redef_alt1.res
index 2deb5ceb4f..8b930a6d6f 100644
--- a/tests/sav/test_serialization_redef_alt1.res
+++ b/tests/sav/test_serialization_redef_alt1.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]}}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]}},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii": 1111,"ss": "\tf\"\r\\/","ffff": 6.789,"bbbb": false,"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"ii":1111,"ss":"\tf\"\r\\/","ffff":6.789,"bbbb":false,"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/sav/test_serialization_redef_alt2.res b/tests/sav/test_serialization_redef_alt2.res
index 1c1850c06a..9662b36a5f 100644
--- a/tests/sav/test_serialization_redef_alt2.res
+++ b/tests/sav/test_serialization_redef_alt2.res
@@ -2,24 +2,24 @@
 <A: true a 0.123 1234 asdf false>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"}
+{"__kind": "obj", "__id": 0, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef"}
 
 # Nit:
 <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false}
+{"__kind": "obj", "__id": 0, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false}
 
 # Nit:
 <C: <A: true a 0.123 1234 asdf false> <B: <A: false b 123.123 2345 hjkl true> 1111 qwer>>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "C","a": {"__kind": "obj", "__id": 1, "__class": "A","b": true,"c": {"__kind": "char", "__val": "a"},"f": 0.123,"i": 1234,"s": "asdf","n": null,"array": {"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef"},"b": {"__kind": "obj", "__id": 3, "__class": "B","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "hjkl","n": 12,"array": {"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "qwer","ffff": 6.789,"bbbb": false},"aa": {"__kind": "ref", "__id": 1}}
+{"__kind": "obj", "__id": 0, "__class": "C","a":{"__kind": "obj", "__id": 1, "__class": "A","b":true,"c":{"__kind": "char", "__val": "a"},"f":0.123,"i":1234,"s":"asdf","n":null,"array":{"__kind": "obj", "__id": 2, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef"},"b":{"__kind": "obj", "__id": 3, "__class": "B","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"hjkl","n":12,"array":{"__kind": "obj", "__id": 4, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"qwer","ffff":6.789,"bbbb":false},"aa":{"__kind": "ref", "__id": 1}}
 
 # Nit:
 <D: <B: <A: false b 123.123 2345 new line ->
 <- false> 1111 	f"
\/> true>
 
 # Json:
-{"__kind": "obj", "__id": 0, "__class": "D","b": false,"c": {"__kind": "char", "__val": "b"},"f": 123.123,"i": 2345,"s": "new line ->\n<-","n": null,"array": {"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii": 6789,"sss": "redef","ii": 1111,"ss": "\tf\"\r\\/","ffff": 6.789,"bbbb": false,"d": {"__kind": "ref", "__id": 0}}
+{"__kind": "obj", "__id": 0, "__class": "D","b":false,"c":{"__kind": "char", "__val": "b"},"f":123.123,"i":2345,"s":"new line ->\n<-","n":null,"array":{"__kind": "obj", "__id": 1, "__class": "Array[nullable Object]","__items": [88,"hello",null]},"iii":6789,"sss":"redef","ii":1111,"ss":"\tf\"\r\\/","ffff":6.789,"bbbb":false,"d":{"__kind": "ref", "__id": 0}}
 
diff --git a/tests/test_json_deserialization.nit b/tests/test_json_deserialization.nit
index 6b936acb44..6a4dfdb0df 100644
--- a/tests/test_json_deserialization.nit
+++ b/tests/test_json_deserialization.nit
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import test_deserialization
-import json::serialization
+import json
 #alt1# import test_deserialization_serial
 #alt3# import test_deserialization_serial
 
diff --git a/tests/test_json_deserialization_heuristic.nit b/tests/test_json_deserialization_heuristic.nit
index c79bba31a1..d0df911253 100644
--- a/tests/test_json_deserialization_heuristic.nit
+++ b/tests/test_json_deserialization_heuristic.nit
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import json::serialization
+import json
 import json::static
 
 class MyData
diff --git a/tests/test_json_deserialization_plain.nit b/tests/test_json_deserialization_plain.nit
index 7358c85db9..da184d592c 100644
--- a/tests/test_json_deserialization_plain.nit
+++ b/tests/test_json_deserialization_plain.nit
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import json::serialization
+import json
 import json::static
 
 class MyClass
diff --git a/tests/test_json_unicode.nit b/tests/test_json_unicode.nit
index 8800f3eb06..84850abb08 100644
--- a/tests/test_json_unicode.nit
+++ b/tests/test_json_unicode.nit
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json::static
 import json
 
 var str = """{
diff --git a/tests/test_serialization.nit b/tests/test_serialization.nit
index b098a8277f..3530f1266b 100644
--- a/tests/test_serialization.nit
+++ b/tests/test_serialization.nit
@@ -17,7 +17,7 @@
 #alt2#module test_serialization_alt2 is serialize
 
 import serialization
-import json::serialization
+import json
 
 # Simple class
 class A