Merge pull request #55223 from mfojtik/fix-proto

Automatic merge from submit-queue (batch tested with PRs 56894, 56940, 55223, 56554, 54985). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Fix protobuf generator for aliases to repeated types

Currently if a type has an alias the generator will fail generating protobuf. This prevents the problem.

```release-note
NONE
```

staging/src/k8s.io/code-generator/cmd/go-to-protobuf/protobuf/generator.go

@@ -516,10 +516,13 @@ func memberTypeToProtobufField(locator ProtobufLocator, field *protoField, t *ty
 				log.Printf("failed to alias: %s %s: err %v", t.Name, t.Underlying.Name, err)
 				return err
 			}
-			if field.Extras == nil {
-				field.Extras = make(map[string]string)
+			// If this is not an alias to a slice, cast to the alias
+			if !field.Repeated {
+				if field.Extras == nil {
+					field.Extras = make(map[string]string)
+				}
+				field.Extras["(gogoproto.casttype)"] = strconv.Quote(locator.CastTypeName(t.Name))
 			}
-			field.Extras["(gogoproto.casttype)"] = strconv.Quote(locator.CastTypeName(t.Name))
 		}
 	case types.Slice:
 		if t.Elem.Name.Name == "byte" && len(t.Elem.Name.Package) == 0 {