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

diff --git a/src/model/model.nit b/src/model/model.nit
index 8e39f9b..03d82b14 100644
--- a/src/model/model.nit
+++ b/src/model/model.nit
@@ -103,6 +103,9 @@ redef class Model
 	# 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]
@@ -252,8 +255,8 @@ redef class MModule
 	# The primitive type `String`
 	var string_type: MClassType = self.get_primitive_class("String").mclass_type is lazy
 
-	# The primitive type `NativeString`
-	var native_string_type: MClassType = self.get_primitive_class("NativeString").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])
@@ -603,7 +606,7 @@ class MClassDef
 	# ENSURE: `bound_mtype.mclass == self.mclass`
 	var bound_mtype: MClassType
 
-	redef var location: Location
+	redef var location
 
 	redef fun visibility do return mclass.visibility
 
@@ -835,14 +838,14 @@ abstract class MType
 		end
 		#print "4.is {sub} a {sup}? <- no more resolution"
 
-		if sub isa MBottomType then
+		if sub isa MBottomType or sub isa MErrorType then
 			return true
 		end
 
 		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 then
+		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
@@ -898,15 +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
@@ -1036,7 +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 conflicts or inconsistencies in the model, the method returns a `MBottomType`.
+	# 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.
@@ -1051,9 +1055,24 @@ 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 `MBottomType`.
+	# 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.
@@ -1121,6 +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
@@ -1134,6 +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
@@ -1200,7 +1221,7 @@ class MClassType
 
 	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
@@ -1352,6 +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
@@ -1395,9 +1434,11 @@ class MVirtualType
 
 	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 or else new MBottomType(model)
+		# 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
@@ -1433,7 +1474,7 @@ class MVirtualType
 
 		var prop = lookup_single_definition(mmodule, resolved_receiver)
 		var res = prop.bound
-		if res == null then return new MBottomType(model)
+		if res == null then return new MErrorType(model)
 
 		# Recursively lookup the fixed result
 		res = res.lookup_fixed(mmodule, resolved_receiver)
@@ -1454,6 +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
@@ -1555,7 +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:
@@ -1668,6 +1713,10 @@ abstract class MProxyType
 		return self.mtype.can_resolve_for(mtype, anchor, mmodule)
 	end
 
+	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)
@@ -1766,7 +1815,7 @@ class MNullType
 	redef fun c_name do return "null"
 	redef fun as_nullable do return self
 
-	redef var as_notnull = new MBottomType(model) is lazy
+	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
@@ -1781,9 +1830,10 @@ 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 absurd, dead, or the absence of knowledge.
+# 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
@@ -1803,6 +1853,31 @@ class MBottomType
 	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]
+
+	redef fun collect_mclasses(mmodule) do return new HashSet[MClass]
+
+	redef fun collect_mtypes(mmodule) do return new HashSet[MClassType]
+end
+
 # A signature of a method
 class MSignature
 	super MType
@@ -2263,6 +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)