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

Commencez par le chemin de traitement des annotations de l’extension Java et la sortie generated-sources/annotations/... décrite dans le rapport ; reproduisez l’écart entre Maven et l’IDE en utilisant le processeur d’annotations référencé et GeneratedInterfaceSpecificMapper. Un projet réduit ou une reproduction équivalente est nécessaire, et le travail est considéré comme terminé lorsque Maven se compile toujours tandis que l’IDE ne signale plus le type généré comme non résolu.