Fix C# optional field reflection when there are regular fields too
Previous tests didn't spot this as each message was either "all
optional" or "all non-optional", at which point there isn't a problem.
diff --git a/csharp/generate_protos.sh b/csharp/generate_protos.sh
index 49a5a42..b663138 100755
--- a/csharp/generate_protos.sh
+++ b/csharp/generate_protos.sh
@@ -45,6 +45,7 @@
# and old_extensions2.proto, which are generated with an older version
# of protoc.
$PROTOC -Isrc -Icsharp/protos \
+ --experimental_allow_proto3_optional \
--csharp_out=csharp/src/Google.Protobuf.Test.TestProtos \
--descriptor_set_out=csharp/src/Google.Protobuf.Test/testprotos.pb \
--include_source_info \
