Liam writes:

There appears to be a javac8 bug that prevents annotation processors from
visiting annotations on parameters. When repeated annotations were
implemented the annotation scanners in JavacProcessingEnvironment
and JavacRoundEnvironment were modified and the following override was 
added:

@Override
public Set<TypeElement> visitExecutable(ExecutableElement e,
Set<TypeElement> p) {
  // Type parameters are not considered to be enclosed by an executable
  scan(e.getTypeParameters(), p);
  return scan(e.getEnclosedElements(), p);
}

MethodSymbols don't have any enclosed elements, but they do have parameters
(which currently aren't being visited). I think that line was meant to
match the base implementation in ElementScanner:

return scan(e.getParameters(), p);