# The C thunk function associated to a mmethoddef. Receives only nullable
	# Object and cast them to the original mmethoddef signature.
	fun callref_thunk(recv_mtype: MClassType): SeparateThunkFunction
	do
		var res = callref_thunk_cache
		if res == null then
			var object_type = mclassdef.mmodule.object_type
			var nullable_object = object_type.as_nullable
			var ps = new Array[MParameter]

			# Replace every argument type by nullable object
			for p in msignature.mparameters do
				ps.push(new MParameter(p.name, nullable_object, p.is_vararg))
			end
			var ret: nullable MType = null
			if msignature.return_mtype != null then ret = nullable_object
			var msignature2 = new MSignature(ps, ret)
			var intromclassdef = mproperty.intro.mclassdef

			res = new SeparateThunkFunction(self, recv_mtype, msignature2, "THUNK_{c_name}", mclassdef.bound_mtype)
			res.polymorph_call_flag = true
			callref_thunk_cache = res
		end
		return res
	end