# Return a class identified by `qid` visible by the module `mmodule`.
	# Visibility in modules and qualified names are correctly handled.
	#
	# If more than one class exists, then null is silently returned.
	# It is up to the caller to post-analysis the result and display a correct error message.
	# The method `class_not_found` can be used to display such a message.
	fun try_get_mclass_by_qid(qid: AQclassid, mmodule: MModule): nullable MClass
	do
		var name = qid.n_id.text

		var classes = model.get_mclasses_by_name(name)
		if classes == null then
			return null
		end

		var res: nullable MClass = null
		for mclass in classes do
			if not mmodule.in_importation <= mclass.intro_mmodule then continue
			if not mmodule.is_visible(mclass.intro_mmodule, mclass.visibility) then continue
			if not qid.accept(mclass) then continue
			if res == null then
				res = mclass
			else
				return null
			end
		end

		return res
	end