MultipleExtractedValue.java

// Should we reject it?
public class DoubleExtractor implements ValueExtractor<Multimap<@ExtractedValue ?, @ExtractedValue ?>> {

  @Override
  public void extractValues(Multimap<?, ?> originalValue, ValueExtractor.ValueReceiver receiver) {
    ...
  }
}

RuntimeVsStaticTypeForExtractorResolution.java

class ListValueExtractor implements ValueExtractor<List<@ExtractedValue ?>> {
  ...
}

class ArrayListValueExtractor implements ValueExtractor<ArrayList<@ExtractedValue ?>> {
  ...
}

// Which extractor should be applied? Constraint validator resolution is happening using the runtime type.
// Should the same be done for extractors? This wouldn't allow to cache it per usage, though.
private List<@Valid String> strings = new ArrayList<>();

SameTypeForKeyAndValueMap.java

interface SameTypeForKeyAndValueMap<T> extends Map<T, T> {}

private SameTypeForKeyAndValueMap<@Valid String> stringToStringMap = ...;

SeveralCascades.java

private Map<String, @Valid Integer> intsByString;

public get Map<@Valid String, Integer> getIntsByString() {
  return intsByString;
}

Some corner cases. What should happen in each of them?