Starting with Truth 1.4.3, compiling on Java 11+ with --release 8 produces a warning:

> Task :grpc-interop-testing:compileJava FAILED
warning: unknown enum constant ElementType.MODULE
error: warnings found and -Werror specified
1 error
1 warning

That warning message is maddening, as it tells you no context to track down the source. It's also maddening that it works on Java 8 but not on Java 11+. I am assuming the problem here is triggered by JSpecify's @NullMarked because its the only reference to ElementType.MODULE I've found to this point. And it appears you've already suffered from it in jspecify/jspecify#302

I get the feeling that the only possible solution, other than "don't use MODULE as we wait for Java 8 to die", is a multi-release jar and tools get updated to support them. But I do wonder if Java 8's death beats that to the finish line (not that anyone can predict Java 8's death).

I don't know what you can do about this. But I'm filing this issue to say "this bit me" and for the moment I'll probably use 1.4.2 in gRPC instead of getting on 1.4.3. I was upgrading from 1.1.5 so that's still a net win for a while.