Add tests for nil routes.

config/staticconfig/route.go

@@ -31,6 +31,9 @@ func analyzeRoute[
 	r ssa.Value,
 ) {
 	switch r := r.(type) {
+	case *ssa.Const:
+		// We've found a nil route.
+
 	case *ssa.MakeInterface:
 		analyzeRoute(ctx, b, r.X)
 

config/staticconfig/testdata/handler-with-nil-route.md

@@ -0,0 +1,37 @@
+# Handler with nil route
+
+This test verifies that the static analyzer correctly detects a `nil` route.
+
+```au:output au:group=matrix
+valid application github.com/dogmatiq/enginekit/config/staticconfig.App (value unavailable)
+  - valid identity app/e4183527-c234-42d5-8709-3dc8b9d5caa4
+  - invalid integration github.com/dogmatiq/enginekit/config/staticconfig.Integration (value unavailable)
+      - no handles-command routes
+      - valid identity handler/5752bb84-0b65-4a7f-b2fa-bfb77a53a97f
+      - incomplete route
+          - route type is unavailable
+          - message type name is unavailable
+```
+
+```go au:input au:group=matrix
+package app
+
+import "context"
+import "github.com/dogmatiq/dogma"
+
+type Integration struct{}
+
+func (Integration) Configure(c dogma.IntegrationConfigurer) {
+	c.Identity("handler", "5752bb84-0b65-4a7f-b2fa-bfb77a53a97f")
+	c.Routes(nil)
+}
+
+func (Integration) HandleCommand(context.Context, dogma.IntegrationCommandScope, dogma.Command) error { return nil }
+
+type App struct{}
+
+func (App) Configure(c dogma.ApplicationConfigurer) {
+	c.Identity("app", "e4183527-c234-42d5-8709-3dc8b9d5caa4")
+	c.RegisterIntegration(Integration{})
+}
+```