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

diff --git a/src/modelize/modelize_class.nit b/src/modelize/modelize_class.nit
index 5cf3e20..853d8ff 100644
--- a/src/modelize/modelize_class.nit
+++ b/src/modelize/modelize_class.nit
@@ -250,13 +250,31 @@ redef class ModelBuilder
 	do
 		var mmodule = nmodule.mmodule
 		if mmodule == null then return
-		var objectclass = try_get_mclass_by_name(nmodule, mmodule, "Object")
-		var pointerclass = try_get_mclass_by_name(nmodule, mmodule, "Pointer")
 		var mclass = nclassdef.mclass
 		if mclass == null then return
 		var mclassdef = nclassdef.mclassdef
 		if mclassdef == null then return
 
+		var supertypes = collect_supertypes(nmodule, nclassdef, mclassdef.is_intro)
+		mclassdef.set_supertypes(supertypes)
+		if not supertypes.is_empty then self.toolcontext.info("{mclassdef} new super-types: {supertypes.join(", ")}", 3)
+	end
+
+	# List the supertypes specified or implied by `nclassdef`.
+	#
+	# REQUIRE: `nmodule.mmodule != null`
+	# REQUIRE: `nclassdef.mclass != null`
+	private fun collect_supertypes(nmodule: AModule, nclassdef: AClassdef,
+			is_intro: Bool): Array[MClassType]
+	do
+		var mmodule = nmodule.mmodule.as(not null)
+		var mclass = nclassdef.mclass.as(not null)
+		var name = mclass.name
+		var kind = mclass.kind
+
+		var objectclass = try_get_mclass_by_name(nmodule, mmodule, "Object")
+		var pointerclass = try_get_mclass_by_name(nmodule, mmodule, "Pointer")
+
 		# Do we need to specify Object as a super class?
 		var specobject = true
 
@@ -273,39 +291,39 @@ redef class ModelBuilder
 						ntype, false)
 				if mtype == null then continue # Skip because of error
 				if not mtype isa MClassType then
-					error(ntype, "Error: supertypes cannot be a formal type.")
-					return
+					error(ntype, "Error: a supertype cannot be a formal type.")
+					continue
 				end
-				if not mclass.kind.can_specialize(mtype.mclass.kind) then
-					error(ntype, "Error: {mclass.kind} `{mclass}` cannot specialize {mtype.mclass.kind} `{mtype.mclass}`.")
+				var superclass = mtype.mclass
+				var super_kind = superclass.kind
+				if not kind.can_specialize(super_kind) then
+					error(ntype, "Error: {kind} `{mclass}` cannot specialize {super_kind} `{superclass}`.")
 				end
 				supertypes.add mtype
 				#print "new super : {mclass} < {mtype}"
-				if mtype.mclass.kind == extern_kind then specpointer = false
+				if super_kind == extern_kind then specpointer = false
 			end
 		end
 
-		if mclassdef.is_intro and objectclass != null then
-			if mclass.kind == extern_kind and mclass.name != "Pointer" then
+		if is_intro and objectclass != null then
+			if kind == extern_kind and name != "Pointer" then
 				# it is an extern class, but not a Pointer
 				if pointerclass == null then
 					error(nclassdef, "Error: `Pointer` must be defined first.")
-					return
+					return supertypes
 				end
 				if specpointer then supertypes.add pointerclass.mclass_type
 			else if specobject then
-				if mclass.name != "Object" then
+				if name != "Object" then
 					# it is a standard class without super class (but is not Object)
 					supertypes.add objectclass.mclass_type
-				else if mclass.kind != interface_kind then
+				else if kind != interface_kind then
 					error(nclassdef, "Error: `Object` must be an {interface_kind}.")
-					return
 				end
 			end
 		end
 
-		mclassdef.set_supertypes(supertypes)
-		if not supertypes.is_empty then self.toolcontext.info("{mclassdef} new super-types: {supertypes.join(", ")}", 3)
+		return supertypes
 	end
 
 	# Check the validity of the specialization heirarchy
@@ -452,8 +470,11 @@ redef class ModelBuilder
 			for nsc in nclassdef.n_superclasses do
 				var ntype = nsc.n_type
 				var mtype = ntype.mtype
-				if mtype == null then continue
-				assert mtype isa MClassType
+
+				# If the supertype is `null` or don’t refer to a class, we
+				# already raised an error.
+				if not mtype isa MClassType then continue
+
 				var sc = mtype.mclass
 				if not parents.has(sc) or sc == objectclass then
 					# Skip the warning on generated code
@@ -517,6 +538,9 @@ end
 redef class AExternClasskind
 	redef fun mkind do return extern_kind
 end
+redef class ASubsetClasskind
+	redef fun mkind do return subset_kind
+end
 
 redef class AFormaldef
 	# The associated parameter type