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

diff --git a/src/model/model.nit b/src/model/model.nit
index a7f570b..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]
@@ -901,12 +904,13 @@ abstract class MType
 	# 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
@@ -1217,7 +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
@@ -1811,7 +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