# Type in C of the extern class
	# If not defined in the intro of this class will look in super-classes
	# FIXME this only supports type definition at intro, extend to superclasses by redef
	private fun compute_ftype(v: ExternClassesTypingPhaseModel): nullable ForeignType
	do
		if ftype_computed then return ftype_cache
		if kind != extern_kind then return null

		# base case
		if name == "Pointer" then
			ftype_cache = new ForeignType
			ftype_computed = true
			return ftype_cache
		end

		var ftype = intro.ftype
		if ftype == null then
			var ftype_b: nullable ForeignType = null # FIXME hack to circumvent bug where ftype is typed null

			# look in super classes
			for s in in_hierarchy(intro_mmodule).direct_greaters do
				var super_ftype = s.compute_ftype(v)
				if super_ftype != null then
					if ftype_b == null then
						ftype_b = super_ftype
						continue
					else
						# detect conflict
						if super_ftype != ftype_b then
							v.toolcontext.error(null, "FFI Error: extern type conflict in `{self}`.")
							return null
						end
					end
				end
			end

			ftype = ftype_b
		end

		ftype_cache = ftype
		ftype_computed = true
		return ftype
	end