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

diff --git a/src/model/model.nit b/src/model/model.nit
index 0d8d6ad..c1c950e 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]
@@ -566,7 +569,12 @@ class MClass
 	# 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
+	redef fun mdoc_or_fallback
+	do
+		# Don’t use `intro.mdoc_or_fallback` because it would create an infinite
+		# recursion.
+		return intro.mdoc
+	end
 end
 
 
@@ -725,6 +733,8 @@ class MClassDef
 
 	# All property introductions and redefinitions (not inheritance) in `self` by its associated property.
 	var mpropdefs_by_property = new HashMap[MProperty, MPropDef]
+
+	redef fun mdoc_or_fallback do return mdoc or else mclass.mdoc_or_fallback
 end
 
 # A global static type
@@ -901,12 +911,13 @@ 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
@@ -1136,6 +1147,7 @@ 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
@@ -1149,6 +1161,7 @@ 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
@@ -1215,7 +1228,7 @@ 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
@@ -1295,6 +1308,7 @@ class MClassType
 	private var collect_mclasses_cache = new HashMap[MModule, Set[MClass]]
 	private var collect_mtypes_cache = new HashMap[MModule, Set[MClassType]]
 
+	redef fun mdoc_or_fallback do return mclass.mdoc_or_fallback
 end
 
 # A type based on a generic class.
@@ -1525,6 +1539,8 @@ class MVirtualType
 	redef fun full_name do return self.mproperty.full_name
 
 	redef fun c_name do return self.mproperty.c_name
+
+	redef fun mdoc_or_fallback do return mproperty.mdoc_or_fallback
 end
 
 # The type associated to a formal parameter generic type of a class
@@ -1809,7 +1825,7 @@ 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
@@ -2049,7 +2065,12 @@ abstract class MProperty
 
 	redef var location
 
-	redef fun mdoc_or_fallback do return intro.mdoc_or_fallback
+	redef fun mdoc_or_fallback
+	do
+		# Don’t use `intro.mdoc_or_fallback` because it would create an infinite
+		# recursion.
+		return intro.mdoc
+	end
 
 	# The canonical name of the property.
 	#
@@ -2471,6 +2492,8 @@ abstract class MPropDef
 		assert has_next_property: i.is_ok
 		return i.item
 	end
+
+	redef fun mdoc_or_fallback do return mdoc or else mproperty.mdoc_or_fallback
 end
 
 # A local definition of a method