proxy: add some interface type assertions

pkg/proxy/config/config.go

@@ -97,6 +97,8 @@ func (*NoopEndpointSliceHandler) OnEndpointSliceDelete(endpointSlice *discovery.
 // OnEndpointSlicesSynced is a noop handler for EndpointSlice syncs.
 func (*NoopEndpointSliceHandler) OnEndpointSlicesSynced() {}
 
+var _ EndpointSliceHandler = &NoopEndpointSliceHandler{}
+
 // EndpointsConfig tracks a set of endpoints configurations.
 type EndpointsConfig struct {
 	listerSynced  cache.InformerSynced
@@ -403,6 +405,8 @@ func (*NoopNodeHandler) OnNodeDelete(node *v1.Node) {}
 // OnNodeSynced is a noop handler for Node syncs.
 func (*NoopNodeHandler) OnNodeSynced() {}
 
+var _ NodeHandler = &NoopNodeHandler{}
+
 // NodeConfig tracks a set of node configurations.
 // It accepts "set", "add" and "remove" operations of node via channels, and invokes registered handlers on change.
 type NodeConfig struct {

pkg/proxy/healthcheck/proxier_health.go

@@ -44,6 +44,8 @@ type ProxierHealthUpdater interface {
 	Updated()
 }
 
+var _ ProxierHealthUpdater = &ProxierHealthServer{}
+
 // ProxierHealthServer returns 200 "OK" by default. It verifies that the delay between
 // QueuedUpdate() calls and Updated() calls never exceeds healthTimeout.
 type ProxierHealthServer struct {

pkg/proxy/iptables/proxier.go

@@ -91,6 +91,8 @@ func CanUseIPTablesProxier(kcompat KernelCompatTester) (bool, error) {
 	return true, nil
 }
 
+var _ KernelCompatTester = LinuxKernelCompatTester{}
+
 // LinuxKernelCompatTester is the Linux implementation of KernelCompatTester
 type LinuxKernelCompatTester struct{}