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

diff --git a/src/model/model.nit b/src/model/model.nit
index 5301e50..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
 
@@ -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
@@ -1058,8 +1062,17 @@ abstract class MType
 	#
 	# `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.
@@ -1127,6 +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
@@ -1140,6 +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
@@ -1206,7 +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
@@ -1364,6 +1379,18 @@ class MGenericType
 		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
@@ -1407,8 +1434,10 @@ 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
+		# 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
 
@@ -1570,7 +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:
@@ -1685,6 +1715,8 @@ abstract class MProxyType
 
 	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)
@@ -1783,7 +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