# Collect the super-types (set by set_supertypes) to build the hierarchy
	#
	# This function can only invoked once by class
	# REQUIRE: `self.in_hierarchy == null`
	# ENSURE: `self.in_hierarchy != null`
	fun add_in_hierarchy
	do
		assert unique_invocation: self.in_hierarchy == null
		var model = mmodule.model
		var res = model.mclassdef_hierarchy.add_node(self)
		self.in_hierarchy = res
		var mtype = self.bound_mtype

		# Here we need to connect the mclassdef to its pairs in the mclassdef_hierarchy
		# The simpliest way is to attach it to collect_mclassdefs
		for mclassdef in mtype.collect_mclassdefs(mmodule) do
			res.poset.add_edge(self, mclassdef)
		end
	end