# Determine the `reassign_property`
	# `readtype` is the type of the reading of the left value.
	# `writetype` is the type of the writing of the left value.
	# (Because of `ACallReassignExpr`, both can be different.
	# Return the static type of the value to store.
	private fun resolve_reassignment(v: TypeVisitor, readtype, writetype: MType): nullable MType
	do
		var reassign_name = self.n_assign_op.operator

		self.read_type = readtype

		var callsite = v.build_callsite_by_name(self.n_assign_op, readtype, reassign_name, false)
		if callsite == null then return null # Skip error
		self.reassign_callsite = callsite

		var msignature = callsite.msignature
		var rettype = msignature.return_mtype
		assert msignature.arity == 1 and rettype != null

		var value_type = v.visit_expr_subtype(self.n_value, msignature.mparameters.first.mtype)
		if value_type == null then return null # Skip error

		v.check_subtype(self, rettype, writetype, false)
		return rettype
	end