# Return the position of the attribute's block of class `cl` in `self` if `cl` has an invariant position in self,
	# Otherwise return a negative position
	fun get_position_attributes(cl: MClass): Int
	do
		# The class has an invariant position in all subclasses
		if cl.position_attributes > 0 then return cl.position_attributes

		# The position has an invariant position for this class and its subclasses only
		if positions_attributes.has_key(cl) then
			var pos = positions_attributes[cl]
			if pos > 0 then return pos
			return -1
		end

		# No invariant position at all, the caller must use a multiple inheritance implementation
		return -1
	end