ipc: Add some type checking statements

Change-Id: I20547b932efc89352a33c6307e01fda9590c6db6
diff --git a/runtimes/google/ipc/stream/manager/listener.go b/runtimes/google/ipc/stream/manager/listener.go
index ef09914..0d67c12 100644
--- a/runtimes/google/ipc/stream/manager/listener.go
+++ b/runtimes/google/ipc/stream/manager/listener.go
@@ -39,6 +39,8 @@
 	vifLoops sync.WaitGroup
 }
 
+var _ stream.Listener = (*netListener)(nil)
+
 // proxyListener implements the listener interface by connecting to a remote
 // proxy (typically used to "listen" across network domains).
 type proxyListener struct {
@@ -48,6 +50,8 @@
 	opts    []stream.ListenerOpt
 }
 
+var _ stream.Listener = (*proxyListener)(nil)
+
 func newNetListener(m *manager, netLn net.Listener, opts []stream.ListenerOpt) listener {
 	ln := &netListener{
 		q:       upcqueue.New(),
diff --git a/runtimes/google/ipc/stream/manager/manager.go b/runtimes/google/ipc/stream/manager/manager.go
index fc5491f..7afdad3 100644
--- a/runtimes/google/ipc/stream/manager/manager.go
+++ b/runtimes/google/ipc/stream/manager/manager.go
@@ -46,6 +46,8 @@
 	shutdown    bool              // GUARDED_BY(muListeners)
 }
 
+var _ stream.Manager = (*manager)(nil)
+
 func dial(network, address string) (net.Conn, error) {
 	if d, _ := stream.RegisteredProtocol(network); d != nil {
 		return d(address)