Annotation processor in project incorrectly yields "[Java] <generated type> cannot be resolved to a type"

I have access to a specific (large) project here which makes use of

@SupportedAnnotationTypes({"the.namespace.TheAnnotation"})
@SupportedSourceVersion(SourceVersion.RELEASE_10)

to create an annotation processor

public class TheAnnotationProcessor extends AbstractProcessor {

for an annotation the.namespace.TheAnnotation in that project

public @interface TheAnnotation {

which produces an interface (e.g. GeneratedInterfaceSpecificMapper, see below) with plenty of default. In the very same project, this annotation is also applied to some classes,

@TheAnnotation(Specific.class)
public class SpecificMapper implements GeneratedInterfaceSpecificMapper {  

Evidently, maven discovers the annotation, the annotation processor, runs code generation through the processor (files appear in generated-sources/annotations/...) and is able to also compile the source files that make use of the GeneratedInterfaceSpecificMapper.

The vscode plugin flags the type GeneratedInterfaceSpecificMapper as faulty, with "[Java] cannot be resolved to a type". This seems to indicate that the vscode plugin is not aware of the generated artefacts in generated-sources/annotations/...

I have had a look at https://www.baeldung.com/java-annotation-processing-builder to see whether this produces the error - alas, that setup there seems to be too clean / too simplistic to trigger the problem.

Environment

• Operating System: Linux Fedora 28
• JDK version: 10.0.2
• Visual Studio Code version: 1.28.2
• Java extension version: java-0.33.0-1252.vsix

Steps To Reproduce

<large project, will try to find time to reduce>

Current Result

• builds fine in maven
• red squiggles in IDE / syntax check failure

Expected Result

• builds fine in maven
• no red squiggles in IDE

Additional Informations

Not sure whether this related to the issues reported for Lombok - e.g #580 or #458

Iniziare dal percorso di elaborazione delle annotazioni dell’estensione Java e dall’output generated-sources/annotations/... descritto nel report; riprodurre la discrepanza tra Maven e l’IDE utilizzando il processore di annotazioni indicato e GeneratedInterfaceSpecificMapper. È necessario un progetto ridotto o una riproduzione equivalente, e il lavoro è completato quando Maven continua a eseguire la build mentre l’IDE non segnala più il tipo generato come non risolto.