having trouble with type constraints around clientIdx

bs/Bus.bs

@@ -67,6 +67,9 @@ mkBus serverMap = do
                 selectedClientRequestQueue = (select clientRequestQueues clientIdx)
             in
                 rules
+                    "rule" : when True ==> do
+                        $display "Bus.bs:71"
+
                     (sprintf "request server from client %d" clientIdx): when True ==> do
                         let
                             clientRequest :: TaggedBusRequest inFlightTransactions
@@ -75,6 +78,7 @@ mkBus serverMap = do
                             targetAddr :: Addr = busRequestToAddr |> clientRequest.busRequest
                             targetServerIdx :: (Maybe ServerIdx) = serverMap targetAddr
                         -- $display "clientRequest" (fshow clientRequest)
+                        $display "Bus.bs:81" (fshow clientRequest)
                         case targetServerIdx of
                             Just serverIdx -> do
                                 let
@@ -83,7 +87,20 @@ mkBus serverMap = do
                                     arbiterClientSlot :: Arbiter.ArbiterClient_IFC
                                     arbiterClientSlot = (select targetServerArbiter.clients clientIdx)
                                 arbiterClientSlot.request
-                            Nothing -> do action {}
+                            Nothing -> do
+                                let
+                                    idx = fromInteger clientIdx
+                                    targetClientResponseArbiter :: Arbiter.Arbiter_IFC numClients
+                                    targetClientResponseArbiter =  (select responseArbiterByClient idx)
+
+                                    clientResponseArbiterSlot :: Arbiter.ArbiterClient_IFC
+                                    -- arbiters 0 to n-1 are where `n:=numServer` are reserved 
+                                    -- for servers to make requests to. Arbiter n is reserved for 
+                                    -- when this rule needs to skip making a request to a server 
+                                    -- and should instead forward the `BusError UnMapped` response
+                                    -- back to the client. Vector.last selects arbiter `n`
+                                    clientResponseArbiterSlot = Vector.last targetClientResponseArbiter
+                                clientResponseArbiterSlot.request