X-Git-Url: http://nitlanguage.org

diff --git a/src/model/model.nit b/src/model/model.nit
index 899f023..03d82b14 100644
--- a/src/model/model.nit
+++ b/src/model/model.nit
@@ -30,6 +30,15 @@ import mdoc
 import ordered_tree
 private import more_collections
 
+redef class MEntity
+	# The visibility of the MEntity.
+	#
+	# MPackages, MGroups and MModules are always public.
+	# The visibility of `MClass` and `MProperty` is defined by the keyword used.
+	# `MClassDef` and `MPropDef` return the visibility of `MClass` and `MProperty`.
+	fun visibility: MVisibility do return public_visibility
+end
+
 redef class Model
 	# All known classes
 	var mclasses = new Array[MClass]
@@ -66,7 +75,7 @@ redef class Model
 	# Collections of classes grouped by their short name
 	private var mclasses_by_name = new MultiHashMap[String, MClass]
 
-	# Return all class named `name`.
+	# Return all classes named `name`.
 	#
 	# If such a class does not exist, null is returned
 	# (instead of an empty array)
@@ -74,11 +83,7 @@ redef class Model
 	# Visibility or modules are not considered
 	fun get_mclasses_by_name(name: String): nullable Array[MClass]
 	do
-		if mclasses_by_name.has_key(name) then
-			return mclasses_by_name[name]
-		else
-			return null
-		end
+		return mclasses_by_name.get_or_null(name)
 	end
 
 	# Collections of properties grouped by their short name
@@ -92,16 +97,15 @@ redef class Model
 	# Visibility or modules are not considered
 	fun get_mproperties_by_name(name: String): nullable Array[MProperty]
 	do
-		if not mproperties_by_name.has_key(name) then
-			return null
-		else
-			return mproperties_by_name[name]
-		end
+		return mproperties_by_name.get_or_null(name)
 	end
 
 	# The only null type
 	var null_type = new MNullType(self)
 
+	# The only bottom type
+	var bottom_type: MBottomType = null_type.as_notnull
+
 	# Build an ordered tree with from `concerns`
 	fun concerns_tree(mconcerns: Collection[MConcern]): ConcernsTree do
 		var seen = new HashSet[MConcern]
@@ -127,7 +131,17 @@ redef class Model
 	end
 end
 
-# An OrderedTree that can be easily refined for display purposes
+# An OrderedTree bound to MEntity.
+#
+# We introduce a new class so it can be easily refined by tools working
+# with a Model.
+class MEntityTree
+	super OrderedTree[MEntity]
+end
+
+# A MEntityTree borned to MConcern.
+#
+# TODO remove when nitdoc is fully merged with model_collect
 class ConcernsTree
 	super OrderedTree[MConcern]
 end
@@ -148,7 +162,7 @@ redef class MModule
 		return self.in_importation <= mclass.intro_mmodule
 	end
 
-	# Full hierarchy of introduced ans imported classes.
+	# Full hierarchy of introduced and imported classes.
 	#
 	# Create a new hierarchy got by flattening the classes for the module
 	# and its imported modules.
@@ -203,31 +217,58 @@ redef class MModule
 	private var flatten_mclass_hierarchy_cache: nullable POSet[MClass] = null
 
 	# The primitive type `Object`, the root of the class hierarchy
-	fun object_type: MClassType
-	do
-		var res = self.object_type_cache
-		if res != null then return res
-		res = self.get_primitive_class("Object").mclass_type
-		self.object_type_cache = res
-		return res
-	end
-
-	private var object_type_cache: nullable MClassType
+	var object_type: MClassType = self.get_primitive_class("Object").mclass_type is lazy
 
 	# The type `Pointer`, super class to all extern classes
 	var pointer_type: MClassType = self.get_primitive_class("Pointer").mclass_type is lazy
 
 	# The primitive type `Bool`
-	fun bool_type: MClassType
-	do
-		var res = self.bool_type_cache
-		if res != null then return res
-		res = self.get_primitive_class("Bool").mclass_type
-		self.bool_type_cache = res
-		return res
-	end
+	var bool_type: MClassType = self.get_primitive_class("Bool").mclass_type is lazy
+
+	# The primitive type `Int`
+	var int_type: MClassType = self.get_primitive_class("Int").mclass_type is lazy
+
+	# The primitive type `Byte`
+	var byte_type: MClassType = self.get_primitive_class("Byte").mclass_type is lazy
+
+	# The primitive type `Int8`
+	var int8_type: MClassType = self.get_primitive_class("Int8").mclass_type is lazy
+
+	# The primitive type `Int16`
+	var int16_type: MClassType = self.get_primitive_class("Int16").mclass_type is lazy
+
+	# The primitive type `UInt16`
+	var uint16_type: MClassType = self.get_primitive_class("UInt16").mclass_type is lazy
+
+	# The primitive type `Int32`
+	var int32_type: MClassType = self.get_primitive_class("Int32").mclass_type is lazy
+
+	# The primitive type `UInt32`
+	var uint32_type: MClassType = self.get_primitive_class("UInt32").mclass_type is lazy
+
+	# The primitive type `Char`
+	var char_type: MClassType = self.get_primitive_class("Char").mclass_type is lazy
+
+	# The primitive type `Float`
+	var float_type: MClassType = self.get_primitive_class("Float").mclass_type is lazy
+
+	# The primitive type `String`
+	var string_type: MClassType = self.get_primitive_class("String").mclass_type is lazy
+
+	# The primitive type `CString`
+	var c_string_type: MClassType = self.get_primitive_class("CString").mclass_type is lazy
+
+	# A primitive type of `Array`
+	fun array_type(elt_type: MType): MClassType do return array_class.get_mtype([elt_type])
+
+	# The primitive class `Array`
+	var array_class: MClass = self.get_primitive_class("Array") is lazy
+
+	# A primitive type of `NativeArray`
+	fun native_array_type(elt_type: MType): MClassType do return native_array_class.get_mtype([elt_type])
 
-	private var bool_type_cache: nullable MClassType
+	# The primitive class `NativeArray`
+	var native_array_class: MClass = self.get_primitive_class("NativeArray") is lazy
 
 	# The primitive type `Sys`, the main type of the program, if any
 	fun sys_type: nullable MClassType
@@ -250,19 +291,27 @@ redef class MModule
 	fun get_primitive_class(name: String): MClass
 	do
 		var cla = self.model.get_mclasses_by_name(name)
-		if cla == null then
-			if name == "Bool" then
-				var c = new MClass(self, name, null, enum_kind, public_visibility)
-				var cladef = new MClassDef(self, c.mclass_type, new Location(null, 0,0,0,0))
+		# Filter classes by introducing module
+		if cla != null then cla = [for c in cla do if self.in_importation <= c.intro_mmodule then c]
+		if cla == null or cla.is_empty then
+			if name == "Bool" and self.model.get_mclasses_by_name("Object") != null then
+				# Bool is injected because it is needed by engine to code the result
+				# of the implicit casts.
+				var loc = model.no_location
+				var c = new MClass(self, name, loc, null, enum_kind, public_visibility)
+				var cladef = new MClassDef(self, c.mclass_type, loc)
+				cladef.set_supertypes([object_type])
+				cladef.add_in_hierarchy
 				return c
 			end
-			print("Fatal Error: no primitive class {name}")
+			print_error("Fatal Error: no primitive class {name} in {self}")
 			exit(1)
+			abort
 		end
 		if cla.length != 1 then
-			var msg = "Fatal Error: more than one primitive class {name}:"
+			var msg = "Fatal Error: more than one primitive class {name} in {self}:"
 			for c in cla do msg += " {c.full_name}"
-			print msg
+			print_error msg
 			#exit(1)
 		end
 		return cla.first
@@ -274,18 +323,15 @@ redef class MModule
 		var props = self.model.get_mproperties_by_name(name)
 		if props == null then return null
 		var res: nullable MMethod = null
+		var recvtype = recv.intro.bound_mtype
 		for mprop in props do
 			assert mprop isa MMethod
-			var intro = mprop.intro_mclassdef
-			for mclassdef in recv.mclassdefs do
-				if not self.in_importation.greaters.has(mclassdef.mmodule) then continue
-				if not mclassdef.in_hierarchy.greaters.has(intro) then continue
-				if res == null then
-					res = mprop
-				else if res != mprop then
-					print("Fatal Error: ambigous property name '{name}'; conflict between {mprop.full_name} and {res.full_name}")
-					abort
-				end
+			if not recvtype.has_mproperty(self, mprop) then continue
+			if res == null then
+				res = mprop
+			else if res != mprop then
+				print_error("Fatal Error: ambigous property name '{name}'; conflict between {mprop.full_name} and {res.full_name}")
+				abort
 			end
 		end
 		return res
@@ -345,19 +391,27 @@ class MClass
 	super MEntity
 
 	# The module that introduce the class
+	#
 	# While classes are not bound to a specific module,
-	# the introducing module is used for naming an visibility
+	# the introducing module is used for naming and visibility.
 	var intro_mmodule: MModule
 
 	# The short name of the class
 	# In Nit, the name of a class cannot evolve in refinements
-	redef var name: String
+	redef var name
+
+	redef var location
 
 	# The canonical name of the class
+	#
+	# It is the name of the class prefixed by the full_name of the `intro_mmodule`
 	# Example: `"owner::module::MyClass"`
-	fun full_name: String
-	do
-		return "{self.intro_mmodule.full_name}::{name}"
+	redef var full_name is lazy do
+		return "{self.intro_mmodule.namespace_for(visibility)}::{name}"
+	end
+
+	redef var c_name is lazy do
+		return "{intro_mmodule.c_namespace_for(visibility)}__{name.to_cmangle}"
 	end
 
 	# The number of generic formal parameters
@@ -368,6 +422,30 @@ class MClass
 	# is empty if the class is not generic
 	var mparameters = new Array[MParameterType]
 
+	# A string version of the signature a generic class.
+	#
+	# eg. `Map[K: nullable Object, V: nullable Object]`
+	#
+	# If the class in non generic the name is just given.
+	#
+	# eg. `Object`
+	fun signature_to_s: String
+	do
+		if arity == 0 then return name
+		var res = new FlatBuffer
+		res.append name
+		res.append "["
+		for i in [0..arity[ do
+			if i > 0 then res.append ", "
+			res.append mparameters[i].name
+			res.append ": "
+			res.append intro.bound_mtype.arguments[i].to_s
+		end
+		res.append "]"
+		return res.to_s
+	end
+
+	# Initialize `mparameters` from their names.
 	protected fun setup_parameter_names(parameter_names: nullable Array[String]) is
 		autoinit
 	do
@@ -400,7 +478,7 @@ class MClass
 
 	# The visibility of the class
 	# In Nit, the visibility of a class cannot evolve in refinements
-	var visibility: MVisibility
+	redef var visibility
 
 	init
 	do
@@ -422,8 +500,17 @@ class MClass
 	#
 	# Warning: such a definition may not exist in the early life of the object.
 	# In this case, the method will abort.
+	#
+	# Use `try_intro` instead
 	var intro: MClassDef is noinit
 
+	# The definition that introduces the class or null if not yet known.
+	#
+	# See `intro`
+	fun try_intro: nullable MClassDef do
+		if isset _intro then return _intro else return null
+	end
+
 	# Return the class `self` in the class hierarchy of the module `mmodule`.
 	#
 	# SEE: `MModule::flatten_mclass_hierarchy`
@@ -435,12 +522,12 @@ class MClass
 
 	# The principal static type of the class.
 	#
-	# For non-generic class, mclass_type is the only `MClassType` based
+	# For non-generic class, `mclass_type` is the only `MClassType` based
 	# on self.
 	#
 	# For a generic class, the arguments are the formal parameters.
-	# i.e.: for the class Array[E:Object], the `mclass_type` is Array[E].
-	# If you want Array[Object] the see `MClassDef::bound_mtype`
+	# i.e.: for the class `Array[E:Object]`, the `mclass_type` is `Array[E]`.
+	# If you want `Array[Object]`, see `MClassDef::bound_mtype`.
 	#
 	# For generic classes, the mclass_type is also the way to get a formal
 	# generic parameter type.
@@ -466,6 +553,23 @@ class MClass
 	end
 
 	private var get_mtype_cache = new HashMap[Array[MType], MGenericType]
+
+	# Is there a `new` factory to allow the pseudo instantiation?
+	var has_new_factory = false is writable
+
+	# Is `self` a standard or abstract class kind?
+	var is_class: Bool is lazy do return kind == concrete_kind or kind == abstract_kind
+
+	# Is `self` an interface kind?
+	var is_interface: Bool is lazy do return kind == interface_kind
+
+	# Is `self` an enum kind?
+	var is_enum: Bool is lazy do return kind == enum_kind
+
+	# Is `self` and abstract class?
+	var is_abstract: Bool is lazy do return kind == abstract_kind
+
+	redef fun mdoc_or_fallback do return intro.mdoc_or_fallback
 end
 
 
@@ -502,12 +606,13 @@ class MClassDef
 	# ENSURE: `bound_mtype.mclass == self.mclass`
 	var bound_mtype: MClassType
 
-	# The origin of the definition
-	var location: Location
+	redef var location
+
+	redef fun visibility do return mclass.visibility
 
 	# Internal name combining the module and the class
-	# Example: "mymodule#MyClass"
-	redef var to_s: String is noinit
+	# Example: "mymodule$MyClass"
+	redef var to_s is noinit
 
 	init
 	do
@@ -518,12 +623,47 @@ class MClassDef
 			assert not isset mclass._intro
 			mclass.intro = self
 		end
-		self.to_s = "{mmodule}#{mclass}"
+		self.to_s = "{mmodule}${mclass}"
 	end
 
 	# Actually the name of the `mclass`
 	redef fun name do return mclass.name
 
+	# The module and class name separated by a '$'.
+	#
+	# The short-name of the class is used for introduction.
+	# Example: "my_module$MyClass"
+	#
+	# The full-name of the class is used for refinement.
+	# Example: "my_module$intro_module::MyClass"
+	redef var full_name is lazy do
+		if is_intro then
+			# public gives 'p$A'
+			# private gives 'p::m$A'
+			return "{mmodule.namespace_for(mclass.visibility)}${mclass.name}"
+		else if mclass.intro_mmodule.mpackage != mmodule.mpackage then
+			# public gives 'q::n$p::A'
+			# private gives 'q::n$p::m::A'
+			return "{mmodule.full_name}${mclass.full_name}"
+		else if mclass.visibility > private_visibility then
+			# public gives 'p::n$A'
+			return "{mmodule.full_name}${mclass.name}"
+		else
+			# private gives 'p::n$::m::A' (redundant p is omitted)
+			return "{mmodule.full_name}$::{mclass.intro_mmodule.name}::{mclass.name}"
+		end
+	end
+
+	redef var c_name is lazy do
+		if is_intro then
+			return "{mmodule.c_namespace_for(mclass.visibility)}___{mclass.c_name}"
+		else if mclass.intro_mmodule.mpackage == mmodule.mpackage and mclass.visibility > private_visibility then
+			return "{mmodule.c_name}___{mclass.name.to_cmangle}"
+		else
+			return "{mmodule.c_name}___{mclass.c_name}"
+		end
+	end
+
 	redef fun model do return mmodule.model
 
 	# All declared super-types
@@ -578,13 +718,16 @@ class MClassDef
 	var in_hierarchy: nullable POSetElement[MClassDef] = null
 
 	# Is the definition the one that introduced `mclass`?
-	fun is_intro: Bool do return mclass.intro == self
+	fun is_intro: Bool do return isset mclass._intro and mclass.intro == self
 
 	# All properties introduced by the classdef
 	var intro_mproperties = new Array[MProperty]
 
-	# All property definitions in the class (introductions and redefinitions)
+	# All property introductions and redefinitions in `self` (not inheritance).
 	var mpropdefs = new Array[MPropDef]
+
+	# All property introductions and redefinitions (not inheritance) in `self` by its associated property.
+	var mpropdefs_by_property = new HashMap[MProperty, MPropDef]
 end
 
 # A global static type
@@ -648,6 +791,8 @@ abstract class MType
 		if sup isa MNullableType then
 			sup_accept_null = true
 			sup = sup.mtype
+		else if sup isa MNotNullType then
+			sup = sup.mtype
 		else if sup isa MNullType then
 			sup_accept_null = true
 		end
@@ -655,16 +800,20 @@ abstract class MType
 		# Can `sub` provide null or not?
 		# Thus we can match with `sup_accept_null`
 		# Also discard the nullable marker if it exists
+		var sub_reject_null = false
 		if sub isa MNullableType then
 			if not sup_accept_null then return false
 			sub = sub.mtype
+		else if sub isa MNotNullType then
+			sub_reject_null = true
+			sub = sub.mtype
 		else if sub isa MNullType then
 			return sup_accept_null
 		end
 		# Now the case of direct null and nullable is over.
 
 		# If `sub` is a formal type, then it is accepted if its bound is accepted
-		while sub isa MParameterType or sub isa MVirtualType do
+		while sub isa MFormalType do
 			#print "3.is {sub} a {sup}?"
 
 			# A unfixed formal type can only accept itself
@@ -672,12 +821,16 @@ abstract class MType
 
 			assert anchor != null
 			sub = sub.lookup_bound(mmodule, anchor)
+			if sub_reject_null then sub = sub.as_notnull
 
 			#print "3.is {sub} a {sup}?"
 
 			# Manage the second layer of null/nullable
 			if sub isa MNullableType then
-				if not sup_accept_null then return false
+				if not sup_accept_null and not sub_reject_null then return false
+				sub = sub.mtype
+			else if sub isa MNotNullType then
+				sub_reject_null = true
 				sub = sub.mtype
 			else if sub isa MNullType then
 				return sup_accept_null
@@ -685,19 +838,19 @@ abstract class MType
 		end
 		#print "4.is {sub} a {sup}? <- no more resolution"
 
-		assert sub isa MClassType # It is the only remaining type
-
-		# A unfixed formal type can only accept itself
-		if sup isa MParameterType or sup isa MVirtualType then
-			return false
+		if sub isa MBottomType or sub isa MErrorType then
+			return true
 		end
 
-		if sup isa MNullType then
-			# `sup` accepts only null
+		assert sub isa MClassType else print_error "{sub} <? {sup}" # It is the only remaining type
+
+		# Handle sup-type when the sub-type is class-based (other cases must have be identified before).
+		if sup isa MFormalType or sup isa MNullType or sup isa MBottomType or sup isa MErrorType then
+			# These types are not super-types of Class-based types.
 			return false
 		end
 
-		assert sup isa MClassType # It is the only remaining type
+		assert sup isa MClassType else print_error "got {sup} {sub.inspect}" # It is the only remaining type
 
 		# Now both are MClassType, we need to dig
 
@@ -748,15 +901,16 @@ abstract class MType
 	#
 	# Explanation of the example:
 	# In H, T is set to B, because "H super G[B]", and U is bound to Y,
-        # because "redef type U: Y". Therefore, Map[T, U] is bound to
+	# because "redef type U: Y". Therefore, Map[T, U] is bound to
 	# Map[B, Y]
 	#
+	# REQUIRE: `self.need_anchor implies anchor != null`
 	# ENSURE: `not self.need_anchor implies result == self`
 	# ENSURE: `not result.need_anchor`
-	fun anchor_to(mmodule: MModule, anchor: MClassType): MType
+	fun anchor_to(mmodule: MModule, anchor: nullable MClassType): MType
 	do
 		if not need_anchor then return self
-		assert not anchor.need_anchor
+		assert anchor != null and not anchor.need_anchor
 		# Just resolve to the anchor and clear all the virtual types
 		var res = self.resolve_for(anchor, null, mmodule, true)
 		assert not res.need_anchor
@@ -886,7 +1040,7 @@ abstract class MType
 	# The result is returned exactly as declared in the "type" property (verbatim).
 	# So it could be another formal type.
 	#
-	# In case of conflict, the method aborts.
+	# In case of conflicts or inconsistencies in the model, the method returns a `MErrorType`.
 	fun lookup_bound(mmodule: MModule, resolved_receiver: MType): MType do return self
 
 	# Resolve the formal type to its simplest equivalent form.
@@ -900,8 +1054,25 @@ abstract class MType
 	#
 	# By default, return self.
 	# See the redefinitions for specific behavior in each kind of type.
+	#
+	# In case of conflicts or inconsistencies in the model, the method returns a `MErrorType`.
 	fun lookup_fixed(mmodule: MModule, resolved_receiver: MType): MType do return self
 
+	# Is the type a `MErrorType` or contains an `MErrorType`?
+	#
+	# `MErrorType` are used in result with conflict or inconsistencies.
+	#
+	# See `is_legal_in` to check conformity with generic bounds.
+	fun is_ok: Bool do return true
+
+	# Is the type legal in a given `mmodule` (with an optional `anchor`)?
+	#
+	# A type is valid if:
+	#
+	# * it does not contain a `MErrorType` (see `is_ok`).
+	# * its generic formal arguments are within their bounds.
+	fun is_legal_in(mmodule: MModule, anchor: nullable MClassType): Bool do return is_ok
+
 	# Can the type be resolved?
 	#
 	# In order to resolve open types, the formal types must make sence.
@@ -939,16 +1110,25 @@ abstract class MType
 		return res
 	end
 
-	# Return the not nullable version of the type
-	# Is the type is already not nullable, then self is returned.
+	# Remove the base type of a decorated (proxy) type.
+	# Is the type is not decorated, then self is returned.
 	#
-	# Note: this just remove the `nullable` notation, but the result can still contains null.
+	# Most of the time it is used to return the not nullable version of a nullable type.
+	# In this case, this just remove the `nullable` notation, but the result can still contains null.
 	# For instance if `self isa MNullType` or self is a formal type bounded by a nullable type.
-	fun as_notnullable: MType
+	# If you really want to exclude the `null` value, then use `as_notnull`
+	fun undecorate: MType
 	do
 		return self
 	end
 
+	# Returns the not null version of the type.
+	# That is `self` minus the `null` value.
+	#
+	# For most types, this return `self`.
+	# For formal types, this returns a special `MNotNullType`
+	fun as_notnull: MType do return self
+
 	private var as_nullable_cache: nullable MType = null
 
 
@@ -960,6 +1140,7 @@ abstract class MType
 	# * H[G[A], B] -> 3
 	#
 	# Formal types have a depth of 1.
+	# Only `MClassType` and `MFormalType` nodes are counted.
 	fun depth: Int
 	do
 		return 1
@@ -973,6 +1154,7 @@ abstract class MType
 	# * H[G[A], B] -> 4
 	#
 	# Formal types have a length of 1.
+	# Only `MClassType` and `MFormalType` nodes are counted.
 	fun length: Int
 	do
 		return 1
@@ -1023,6 +1205,8 @@ class MClassType
 
 	redef fun model do return self.mclass.intro_mmodule.model
 
+	redef fun location do return mclass.location
+
 	# TODO: private init because strongly bounded to its mclass. see `mclass.mclass_type`
 
 	# The formal arguments of the type
@@ -1031,9 +1215,13 @@ class MClassType
 
 	redef fun to_s do return mclass.to_s
 
+	redef fun full_name do return mclass.full_name
+
+	redef fun c_name do return mclass.c_name
+
 	redef fun need_anchor do return false
 
-	redef fun anchor_to(mmodule: MModule, anchor: MClassType): MClassType
+	redef fun anchor_to(mmodule, anchor): MClassType
 	do
 		return super.as(MClassType)
 	end
@@ -1139,11 +1327,31 @@ class MGenericType
 		self.to_s = "{mclass}[{arguments.join(", ")}]"
 	end
 
-	# Recursively print the type of the arguments within brackets.
+	# The short-name of the class, then the full-name of each type arguments within brackets.
 	# Example: `"Map[String, List[Int]]"`
-	redef var to_s: String is noinit
+	redef var to_s is noinit
 
-	redef var need_anchor: Bool is noinit
+	# The full-name of the class, then the full-name of each type arguments within brackets.
+	# Example: `"core::Map[core::String, core::List[core::Int]]"`
+	redef var full_name is lazy do
+		var args = new Array[String]
+		for t in arguments do
+			args.add t.full_name
+		end
+		return "{mclass.full_name}[{args.join(", ")}]"
+	end
+
+	redef var c_name is lazy do
+		var res = mclass.c_name
+		# Note: because the arity is known, a prefix notation is enough
+		for t in arguments do
+			res += "__"
+			res += t.c_name
+		end
+		return res.to_s
+	end
+
+	redef var need_anchor is noinit
 
 	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual)
 	do
@@ -1165,6 +1373,24 @@ class MGenericType
 		return true
 	end
 
+	redef fun is_ok
+	do
+		for t in arguments do if not t.is_ok then return false
+		return super
+	end
+
+	redef fun is_legal_in(mmodule, anchor)
+	do
+		var mtype
+		if need_anchor then
+			assert anchor != null
+			mtype = anchor_to(mmodule, anchor)
+		else
+			mtype = self
+		end
+		if not mtype.is_ok then return false
+		return mtype.is_subtype(mmodule, null, mtype.mclass.intro.bound_mtype)
+	end
 
 	redef fun depth
 	do
@@ -1186,19 +1412,33 @@ class MGenericType
 	end
 end
 
+# A formal type (either virtual of parametric).
+#
+# The main issue with formal types is that they offer very little information on their own
+# and need a context (anchor and mmodule) to be useful.
+abstract class MFormalType
+	super MType
+
+	redef var as_notnull = new MNotNullType(self) is lazy
+end
+
 # A virtual formal type.
 class MVirtualType
-	super MType
+	super MFormalType
 
 	# The property associated with the type.
 	# Its the definitions of this property that determine the bound or the virtual type.
 	var mproperty: MVirtualTypeProp
 
+	redef fun location do return mproperty.location
+
 	redef fun model do return self.mproperty.intro_mclassdef.mmodule.model
 
-	redef fun lookup_bound(mmodule: MModule, resolved_receiver: MType): MType
+	redef fun lookup_bound(mmodule, resolved_receiver)
 	do
-		return lookup_single_definition(mmodule, resolved_receiver).bound.as(not null)
+		# There is two possible invalid cases: the vt does not exists in resolved_receiver or the bound is broken
+		if not resolved_receiver.has_mproperty(mmodule, mproperty) then return new MErrorType(model)
+		return lookup_single_definition(mmodule, resolved_receiver).bound or else new MErrorType(model)
 	end
 
 	private fun lookup_single_definition(mmodule: MModule, resolved_receiver: MType): MVirtualTypeDef
@@ -1229,11 +1469,12 @@ class MVirtualType
 	redef fun lookup_fixed(mmodule: MModule, resolved_receiver: MType): MType
 	do
 		assert not resolved_receiver.need_anchor
-		resolved_receiver = resolved_receiver.as_notnullable
+		resolved_receiver = resolved_receiver.undecorate
 		assert resolved_receiver isa MClassType # It is the only remaining type
 
 		var prop = lookup_single_definition(mmodule, resolved_receiver)
-		var res = prop.bound.as(not null)
+		var res = prop.bound
+		if res == null then return new MErrorType(model)
 
 		# Recursively lookup the fixed result
 		res = res.lookup_fixed(mmodule, resolved_receiver)
@@ -1254,6 +1495,9 @@ class MVirtualType
 	do
 		if not cleanup_virtual then return self
 		assert can_resolve_for(mtype, anchor, mmodule)
+
+		if mproperty.is_selftype then return mtype
+
 		# self is a virtual type declared (or inherited) in mtype
 		# The point of the function it to get the bound of the virtual type that make sense for mtype
 		# But because mtype is maybe a virtual/formal type, we need to get a real receiver first
@@ -1283,6 +1527,10 @@ class MVirtualType
 	end
 
 	redef fun to_s do return self.mproperty.to_s
+
+	redef fun full_name do return self.mproperty.full_name
+
+	redef fun c_name do return self.mproperty.c_name
 end
 
 # The type associated to a formal parameter generic type of a class
@@ -1312,13 +1560,15 @@ end
 # Note that parameter types are shared among class refinements.
 # Therefore parameter only have an internal name (see `to_s` for details).
 class MParameterType
-	super MType
+	super MFormalType
 
 	# The generic class where the parameter belong
 	var mclass: MClass
 
 	redef fun model do return self.mclass.intro_mmodule.model
 
+	redef fun location do return mclass.location
+
 	# The position of the parameter (0 for the first parameter)
 	# FIXME: is `position` a better name?
 	var rank: Int
@@ -1327,10 +1577,14 @@ class MParameterType
 
 	redef fun to_s do return name
 
+	redef var full_name is lazy do return "{mclass.full_name}::{name}"
+
+	redef var c_name is lazy do return mclass.c_name + "__" + "#{name}".to_cmangle
+
 	redef fun lookup_bound(mmodule: MModule, resolved_receiver: MType): MType
 	do
 		assert not resolved_receiver.need_anchor
-		resolved_receiver = resolved_receiver.as_notnullable
+		resolved_receiver = resolved_receiver.undecorate
 		assert resolved_receiver isa MClassType # It is the only remaining type
 		var goalclass = self.mclass
 		if resolved_receiver.mclass == goalclass then
@@ -1345,7 +1599,8 @@ class MParameterType
 				return res
 			end
 		end
-		abort
+		# Cannot found `self` in `resolved_receiver`
+		return new MErrorType(model)
 	end
 
 	# A PT is fixed when:
@@ -1358,7 +1613,7 @@ class MParameterType
 	redef fun lookup_fixed(mmodule: MModule, resolved_receiver: MType): MType
 	do
 		assert not resolved_receiver.need_anchor
-		resolved_receiver = resolved_receiver.as_notnullable
+		resolved_receiver = resolved_receiver.undecorate
 		assert resolved_receiver isa MClassType # It is the only remaining type
 		var res = self.resolve_for(resolved_receiver.mclass.mclass_type, resolved_receiver, mmodule, false)
 		return res
@@ -1392,6 +1647,7 @@ class MParameterType
 		end
 		if resolved_receiver isa MNullableType then resolved_receiver = resolved_receiver.mtype
 		if resolved_receiver isa MParameterType then
+			assert anchor != null
 			assert resolved_receiver.mclass == anchor.mclass
 			resolved_receiver = anchor.arguments[resolved_receiver.rank]
 			if resolved_receiver isa MNullableType then resolved_receiver = resolved_receiver.mtype
@@ -1430,29 +1686,26 @@ class MParameterType
 	end
 end
 
-# A type prefixed with "nullable"
-class MNullableType
+# A type that decorates another type.
+#
+# The point of this class is to provide a common implementation of sevices that just forward to the original type.
+# Specific decorator are expected to redefine (or to extend) the default implementation as this suit them.
+abstract class MProxyType
 	super MType
-
-	# The base type of the nullable type
+	# The base type
 	var mtype: MType
 
-	redef fun model do return self.mtype.model
-
-	init
-	do
-		self.to_s = "nullable {mtype}"
-	end
-
-	redef var to_s: String is noinit
+	redef fun location do return mtype.location
 
+	redef fun model do return self.mtype.model
 	redef fun need_anchor do return mtype.need_anchor
-	redef fun as_nullable do return self
-	redef fun as_notnullable do return mtype
+	redef fun as_nullable do return mtype.as_nullable
+	redef fun as_notnull do return mtype.as_notnull
+	redef fun undecorate do return mtype.undecorate
 	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual)
 	do
 		var res = self.mtype.resolve_for(mtype, anchor, mmodule, cleanup_virtual)
-		return res.as_nullable
+		return res
 	end
 
 	redef fun can_resolve_for(mtype, anchor, mmodule)
@@ -1460,12 +1713,14 @@ class MNullableType
 		return self.mtype.can_resolve_for(mtype, anchor, mmodule)
 	end
 
-	# Efficiently returns `mtype.lookup_fixed(mmodule, resolved_receiver).as_nullable`
+	redef fun is_ok do return mtype.is_ok
+
+	redef fun is_legal_in(mmodule, anchor) do return mtype.is_legal_in(mmodule, anchor)
+
 	redef fun lookup_fixed(mmodule, resolved_receiver)
 	do
 		var t = mtype.lookup_fixed(mmodule, resolved_receiver)
-		if t == mtype then return self
-		return t.as_nullable
+		return t
 	end
 
 	redef fun depth do return self.mtype.depth
@@ -1491,17 +1746,130 @@ class MNullableType
 	end
 end
 
+# A type prefixed with "nullable"
+class MNullableType
+	super MProxyType
+
+	init
+	do
+		self.to_s = "nullable {mtype}"
+	end
+
+	redef var to_s is noinit
+
+	redef var full_name is lazy do return "nullable {mtype.full_name}"
+
+	redef var c_name is lazy do return "nullable__{mtype.c_name}"
+
+	redef fun as_nullable do return self
+	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual)
+	do
+		var res = super
+		return res.as_nullable
+	end
+
+	# Efficiently returns `mtype.lookup_fixed(mmodule, resolved_receiver).as_nullable`
+	redef fun lookup_fixed(mmodule, resolved_receiver)
+	do
+		var t = super
+		if t == mtype then return self
+		return t.as_nullable
+	end
+end
+
+# A non-null version of a formal type.
+#
+# When a formal type in bounded to a nullable type, this is the type of the not null version of it.
+class MNotNullType
+	super MProxyType
+
+	redef fun to_s do return "not null {mtype}"
+	redef var full_name is lazy do return "not null {mtype.full_name}"
+	redef var c_name is lazy do return "notnull__{mtype.c_name}"
+
+	redef fun as_notnull do return self
+
+	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual)
+	do
+		var res = super
+		return res.as_notnull
+	end
+
+	# Efficiently returns `mtype.lookup_fixed(mmodule, resolved_receiver).as_notnull`
+	redef fun lookup_fixed(mmodule, resolved_receiver)
+	do
+		var t = super
+		if t == mtype then return self
+		return t.as_notnull
+	end
+end
+
 # The type of the only value null
 #
 # The is only one null type per model, see `MModel::null_type`.
 class MNullType
 	super MType
-	redef var model: Model
+	redef var model
 	redef fun to_s do return "null"
+	redef fun full_name do return "null"
+	redef fun c_name do return "null"
 	redef fun as_nullable do return self
+
+	redef var as_notnull: MBottomType = new MBottomType(model) is lazy
+	redef fun need_anchor do return false
+	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual) do return self
+	redef fun can_resolve_for(mtype, anchor, mmodule) do return true
+
+	redef fun collect_mclassdefs(mmodule) do return new HashSet[MClassDef]
+
+	redef fun collect_mclasses(mmodule) do return new HashSet[MClass]
+
+	redef fun collect_mtypes(mmodule) do return new HashSet[MClassType]
+end
+
+# The special universal most specific type.
+#
+# This type is intended to be only used internally for type computation or analysis and should not be exposed to the user.
+# The bottom type can de used to denote things that are dead (no instance).
+#
+# Semantically it is the singleton `null.as_notnull`.
+# Is also means that `self.as_nullable == null`.
+class MBottomType
+	super MType
+	redef var model
+	redef fun to_s do return "bottom"
+	redef fun full_name do return "bottom"
+	redef fun c_name do return "bottom"
+	redef fun as_nullable do return model.null_type
+	redef fun as_notnull do return self
+	redef fun need_anchor do return false
+	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual) do return self
+	redef fun can_resolve_for(mtype, anchor, mmodule) do return true
+
+	redef fun collect_mclassdefs(mmodule) do return new HashSet[MClassDef]
+
+	redef fun collect_mclasses(mmodule) do return new HashSet[MClass]
+
+	redef fun collect_mtypes(mmodule) do return new HashSet[MClassType]
+end
+
+# A special type used as a silent error marker when building types.
+#
+# This type is intended to be only used internally for type operation and should not be exposed to the user.
+# The error type can de used to denote things that are conflicting or inconsistent.
+#
+# Some methods on types can return a `MErrorType` to denote a broken or a conflicting result.
+# Use `is_ok` to check if a type is (or contains) a `MErrorType` .
+class MErrorType
+	super MType
+	redef var model
+	redef fun to_s do return "error"
+	redef fun full_name do return "error"
+	redef fun c_name do return "error"
 	redef fun need_anchor do return false
 	redef fun resolve_for(mtype, anchor, mmodule, cleanup_virtual) do return self
 	redef fun can_resolve_for(mtype, anchor, mmodule) do return true
+	redef fun is_ok do return false
 
 	redef fun collect_mclassdefs(mmodule) do return new HashSet[MClassDef]
 
@@ -1517,6 +1885,15 @@ class MSignature
 	# The each parameter (in order)
 	var mparameters: Array[MParameter]
 
+	# Returns a parameter named `name`, if any.
+	fun mparameter_by_name(name: String): nullable MParameter
+	do
+		for p in mparameters do
+			if p.name == name then return p
+		end
+		return null
+	end
+
 	# The return type (null for a procedure)
 	var return_mtype: nullable MType
 
@@ -1550,19 +1927,29 @@ class MSignature
 		for i in [0..mparameters.length[ do
 			var parameter = mparameters[i]
 			if parameter.is_vararg then
-				assert vararg_rank == -1
+				if vararg_rank >= 0 then
+					# If there is more than one vararg,
+					# consider that additional arguments cannot be mapped.
+					vararg_rank = -1
+					break
+				end
 				vararg_rank = i
 			end
 		end
 		self.vararg_rank = vararg_rank
 	end
 
-	# The rank of the ellipsis (`...`) for vararg (starting from 0).
+	# The rank of the main ellipsis (`...`) for vararg (starting from 0).
 	# value is -1 if there is no vararg.
 	# Example: for "(a: Int, b: Bool..., c: Char)" #-> vararg_rank=1
+	#
+	# From a model POV, a signature can contain more than one vararg parameter,
+	# the `vararg_rank` just indicates the one that will receive the additional arguments.
+	# However, currently, if there is more that one vararg parameter, no one will be the main one,
+	# and additional arguments will be refused.
 	var vararg_rank: Int is noinit
 
-	# The number or parameters
+	# The number of parameters
 	fun arity: Int do return mparameters.length
 
 	redef fun to_s
@@ -1610,7 +1997,7 @@ class MParameter
 	super MEntity
 
 	# The name of the parameter
-	redef var name: String
+	redef var name
 
 	# The static type of the parameter
 	var mtype: MType
@@ -1627,6 +2014,8 @@ class MParameter
 		end
 	end
 
+	# Returns a new parameter with the `mtype` resolved.
+	# See `MType::resolve_for` for details.
 	fun resolve_for(mtype: MType, anchor: nullable MClassType, mmodule: MModule, cleanup_virtual: Bool): MParameter
 	do
 		if not self.mtype.need_anchor then return self
@@ -1662,17 +2051,41 @@ abstract class MProperty
 	var intro_mclassdef: MClassDef
 
 	# The (short) name of the property
-	redef var name: String
+	redef var name
 
-	# The canonical name of the property
-	# Example: "owner::my_module::MyClass::my_method"
-	fun full_name: String
-	do
-		return "{self.intro_mclassdef.mmodule.full_name}::{self.intro_mclassdef.mclass.name}::{name}"
+	redef var location
+
+	redef fun mdoc_or_fallback do return intro.mdoc_or_fallback
+
+	# The canonical name of the property.
+	#
+	# It is currently the short-`name` prefixed by the short-name of the class and the full-name of the module.
+	# Example: "my_package::my_module::MyClass::my_method"
+	#
+	# The full-name of the module is needed because two distinct modules of the same package can
+	# still refine the same class and introduce homonym properties.
+	#
+	# For public properties not introduced by refinement, the module name is not used.
+	#
+	# Example: `my_package::MyClass::My_method`
+	redef var full_name is lazy do
+		if intro_mclassdef.is_intro then
+			return "{intro_mclassdef.mmodule.namespace_for(visibility)}::{intro_mclassdef.mclass.name}::{name}"
+		else
+			return "{intro_mclassdef.mmodule.full_name}::{intro_mclassdef.mclass.name}::{name}"
+		end
+	end
+
+	redef var c_name is lazy do
+		# FIXME use `namespace_for`
+		return "{intro_mclassdef.mmodule.c_name}__{intro_mclassdef.mclass.name.to_cmangle}__{name.to_cmangle}"
 	end
 
 	# The visibility of the property
-	var visibility: MVisibility
+	redef var visibility
+
+	# Is the property usable as an initializer?
+	var is_autoinit = false is writable
 
 	init
 	do
@@ -1704,10 +2117,13 @@ abstract class MProperty
 	# If mtype does not know mproperty then an empty array is returned.
 	#
 	# If you want the really most specific property, then look at `lookup_first_definition`
+	#
+	# REQUIRE: `not mtype.need_anchor` to simplify the API (no `anchor` parameter)
+	# ENSURE: `not mtype.has_mproperty(mmodule, self) == result.is_empty`
 	fun lookup_definitions(mmodule: MModule, mtype: MType): Array[MPROPDEF]
 	do
 		assert not mtype.need_anchor
-		mtype = mtype.as_notnullable
+		mtype = mtype.undecorate
 
 		var cache = self.lookup_definitions_cache[mmodule, mtype]
 		if cache != null then return cache
@@ -1715,14 +2131,27 @@ abstract class MProperty
 		#print "select prop {mproperty} for {mtype} in {self}"
 		# First, select all candidates
 		var candidates = new Array[MPROPDEF]
-		for mpropdef in self.mpropdefs do
-			# If the definition is not imported by the module, then skip
-			if not mmodule.in_importation <= mpropdef.mclassdef.mmodule then continue
-			# If the definition is not inherited by the type, then skip
-			if not mtype.is_subtype(mmodule, null, mpropdef.mclassdef.bound_mtype) then continue
-			# Else, we keep it
-			candidates.add(mpropdef)
+
+		# Here we have two strategies: iterate propdefs or iterate classdefs.
+		var mpropdefs = self.mpropdefs
+		if mpropdefs.length <= 1 or mpropdefs.length < mtype.collect_mclassdefs(mmodule).length then
+			# Iterate on all definitions of `self`, keep only those inherited by `mtype` in `mmodule`
+			for mpropdef in mpropdefs do
+				# If the definition is not imported by the module, then skip
+				if not mmodule.in_importation <= mpropdef.mclassdef.mmodule then continue
+				# If the definition is not inherited by the type, then skip
+				if not mtype.is_subtype(mmodule, null, mpropdef.mclassdef.bound_mtype) then continue
+				# Else, we keep it
+				candidates.add(mpropdef)
+			end
+		else
+			# Iterate on all super-classdefs of `mtype`, keep only the definitions of `self`, if any.
+			for mclassdef in mtype.collect_mclassdefs(mmodule) do
+				var p = mclassdef.mpropdefs_by_property.get_or_null(self)
+				if p != null then candidates.add p
+			end
 		end
+
 		# Fast track for only one candidate
 		if candidates.length <= 1 then
 			self.lookup_definitions_cache[mmodule, mtype] = candidates
@@ -1742,11 +2171,12 @@ abstract class MProperty
 	#
 	# If you want the really most specific property, then look at `lookup_next_definition`
 	#
-	# FIXME: Move to `MPropDef`?
+	# REQUIRE: `not mtype.need_anchor` to simplify the API (no `anchor` parameter)
+	# ENSURE: `not mtype.has_mproperty(mmodule, self) implies result.is_empty`
 	fun lookup_super_definitions(mmodule: MModule, mtype: MType): Array[MPROPDEF]
 	do
 		assert not mtype.need_anchor
-		mtype = mtype.as_notnullable
+		mtype = mtype.undecorate
 
 		# First, select all candidates
 		var candidates = new Array[MPROPDEF]
@@ -1797,7 +2227,7 @@ abstract class MProperty
 			end
 		end
 		if res.is_empty then
-			print "All lost! {candidates.join(", ")}"
+			print_error "All lost! {candidates.join(", ")}"
 			# FIXME: should be abort!
 		end
 		return res
@@ -1810,24 +2240,28 @@ abstract class MProperty
 	#
 	# FIXME: the linearization is still unspecified
 	#
-	# REQUIRE: `not mtype.need_anchor`
+	# REQUIRE: `not mtype.need_anchor` to simplify the API (no `anchor` parameter)
 	# REQUIRE: `mtype.has_mproperty(mmodule, self)`
 	fun lookup_first_definition(mmodule: MModule, mtype: MType): MPROPDEF
 	do
-		assert mtype.has_mproperty(mmodule, self)
 		return lookup_all_definitions(mmodule, mtype).first
 	end
 
 	# Return all definitions in a linearization order
 	# Most specific first, most general last
+	#
+	# REQUIRE: `not mtype.need_anchor` to simplify the API (no `anchor` parameter)
+	# REQUIRE: `mtype.has_mproperty(mmodule, self)`
 	fun lookup_all_definitions(mmodule: MModule, mtype: MType): Array[MPROPDEF]
 	do
-		assert not mtype.need_anchor
-		mtype = mtype.as_notnullable
+		mtype = mtype.undecorate
 
 		var cache = self.lookup_all_definitions_cache[mmodule, mtype]
 		if cache != null then return cache
 
+		assert not mtype.need_anchor
+		assert mtype.has_mproperty(mmodule, self)
+
 		#print "select prop {mproperty} for {mtype} in {self}"
 		# First, select all candidates
 		var candidates = new Array[MPROPDEF]
@@ -1882,6 +2316,10 @@ class MMethod
 	do
 		return self.is_init
 	end
+
+	# A specific method that is safe to call on null.
+	# Currently, only `==`, `!=` and `is_same_instance` are safe
+	fun is_null_safe: Bool do return name == "==" or name == "!=" or name == "is_same_instance"
 end
 
 # A global attribute
@@ -1900,6 +2338,9 @@ class MVirtualTypeProp
 
 	# The formal type associated to the virtual type property
 	var mvirtualtype = new MVirtualType(self)
+
+	# Is `self` the special virtual type `SELF`?
+	var is_selftype: Bool is lazy do return name == "SELF"
 end
 
 # A definition of a property (local property)
@@ -1922,31 +2363,102 @@ abstract class MPropDef
 	# The associated global property
 	var mproperty: MPROPERTY
 
-	# The origin of the definition
-	var location: Location
+	redef var location: Location
+
+	redef fun visibility do return mproperty.visibility
 
 	init
 	do
 		mclassdef.mpropdefs.add(self)
 		mproperty.mpropdefs.add(self)
+		mclassdef.mpropdefs_by_property[mproperty] = self
 		if mproperty.intro_mclassdef == mclassdef then
 			assert not isset mproperty._intro
 			mproperty.intro = self
 		end
-		self.to_s = "{mclassdef}#{mproperty}"
+		self.to_s = "{mclassdef}${mproperty}"
 	end
 
 	# Actually the name of the `mproperty`
 	redef fun name do return mproperty.name
 
+	# The full-name of mpropdefs combine the information about the `classdef` and the `mproperty`.
+	#
+	# Therefore the combination of identifiers is awful,
+	# the worst case being
+	#
+	#  * a property "p::m::A::x"
+	#  * redefined in a refinement of a class "q::n::B"
+	#  * in a module "r::o"
+	#  * so "r::o$q::n::B$p::m::A::x"
+	#
+	# Fortunately, the full-name is simplified when entities are repeated.
+	# For the previous case, the simplest form is "p$A$x".
+	redef var full_name is lazy do
+		var res = new FlatBuffer
+
+		# The first part is the mclassdef. Worst case is "r::o$q::n::B"
+		res.append mclassdef.full_name
+
+		res.append "$"
+
+		if mclassdef.mclass == mproperty.intro_mclassdef.mclass then
+			# intro are unambiguous in a class
+			res.append name
+		else
+			# Just try to simplify each part
+			if mclassdef.mmodule.mpackage != mproperty.intro_mclassdef.mmodule.mpackage then
+				# precise "p::m" only if "p" != "r"
+				res.append mproperty.intro_mclassdef.mmodule.namespace_for(mproperty.visibility)
+				res.append "::"
+			else if mproperty.visibility <= private_visibility then
+				# Same package ("p"=="q"), but private visibility,
+				# does the module part ("::m") need to be displayed
+				if mclassdef.mmodule.namespace_for(mclassdef.mclass.visibility) != mproperty.intro_mclassdef.mmodule.mpackage then
+					res.append "::"
+					res.append mproperty.intro_mclassdef.mmodule.name
+					res.append "::"
+				end
+			end
+			if mclassdef.mclass != mproperty.intro_mclassdef.mclass then
+				# precise "B" only if not the same class than "A"
+				res.append mproperty.intro_mclassdef.name
+				res.append "::"
+			end
+			# Always use the property name "x"
+			res.append mproperty.name
+		end
+		return res.to_s
+	end
+
+	redef var c_name is lazy do
+		var res = new FlatBuffer
+		res.append mclassdef.c_name
+		res.append "___"
+		if mclassdef.mclass == mproperty.intro_mclassdef.mclass then
+			res.append name.to_cmangle
+		else
+			if mclassdef.mmodule != mproperty.intro_mclassdef.mmodule then
+				res.append mproperty.intro_mclassdef.mmodule.c_name
+				res.append "__"
+			end
+			if mclassdef.mclass != mproperty.intro_mclassdef.mclass then
+				res.append mproperty.intro_mclassdef.name.to_cmangle
+				res.append "__"
+			end
+			res.append mproperty.name.to_cmangle
+		end
+		return res.to_s
+	end
+
 	redef fun model do return mclassdef.model
 
 	# Internal name combining the module, the class and the property
-	# Example: "mymodule#MyClass#mymethod"
-	redef var to_s: String is noinit
+	# Example: "mymodule$MyClass$mymethod"
+	redef var to_s is noinit
 
 	# Is self the definition that introduce the property?
-	fun is_intro: Bool do return mproperty.intro == self
+	fun is_intro: Bool do return isset mproperty._intro and mproperty.intro == self
 
 	# Return the next definition in linearization of `mtype`.
 	#
@@ -2046,7 +2558,7 @@ end
 # Note this class is basically an enum.
 # FIXME: use a real enum once user-defined enums are available
 class MClassKind
-	redef var to_s: String
+	redef var to_s
 
 	# Is a constructor required?
 	var need_init: Bool