Consider the following:
When the compiler accesses the annotations of a pre-compiled Example through the ClassNode Sample, the AnnotationCollector mode attribute is null. This can be problematic for AST transformations which rely on the Groovy model for the annotation metadata.
In my real-world example, I had a record type, which has the implicit annotation RecordType. When I added an explicit TupleConstructor annotation, the attributes were not merged, so I received duplicate processing of TupleConstructor and therefore duplicate constructors.