# Return a generic type based on the class
	# Is the class is not generic, then the result is `mclass_type`
	#
	# REQUIRE: `mtype_arguments.length == self.arity`
	fun get_mtype(mtype_arguments: Array[MType]): MClassType
	do
		assert mtype_arguments.length == self.arity
		if self.arity == 0 then return self.mclass_type
		var res = get_mtype_cache.get_or_null(mtype_arguments)
		if res != null then return res
		res = new MGenericType(self, mtype_arguments)
		self.get_mtype_cache[mtype_arguments.to_a] = res
		return res
	end