What version of protobuf and what language are you using?

Version: master, but problem exists since at least 3.11
Language: C++

What operating system (Linux, Windows, ...) and version?

Linux, multiple versions.

What runtime / compiler are you using (e.g., python version or gcc version)

GCC 5.4

What did you do?

Compile the protos in https://github.com/googleapis/googleapis

What did you expect to see

Code compiles correctly

What did you see instead?

https://godbolt.org/z/KrK8vr

Anything else we should know about your project / environment