KT-6178 False "Overriden methods are not annotated" when using delegation

#KT-6178 Fixed

compiler/backend/src/org/jetbrains/jet/codegen/AnnotationCodegen.java

@@ -33,6 +33,7 @@ import org.jetbrains.jet.lang.resolve.BindingContext;
 import org.jetbrains.jet.lang.resolve.calls.model.ResolvedCall;
 import org.jetbrains.jet.lang.resolve.constants.*;
 import org.jetbrains.jet.lang.resolve.constants.StringValue;
+import org.jetbrains.jet.lang.resolve.java.JvmAnnotationNames;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.types.Flexibility;
 import org.jetbrains.jet.lang.types.JetType;
@@ -189,7 +190,12 @@ public abstract class AnnotationCodegen {
         if (TypesPackage.isFlexible(type)) {
             // A flexible type whose lower bound in not-null and upper bound is nullable, should not be annotated
             Flexibility flexibility = TypesPackage.flexibility(type);
+
             if (!TypeUtils.isNullableType(flexibility.getLowerBound()) && TypeUtils.isNullableType(flexibility.getUpperBound())) {
+                AnnotationDescriptor notNull = type.getAnnotations().findAnnotation(JvmAnnotationNames.JETBRAINS_NOT_NULL_ANNOTATION);
+                if (notNull != null) {
+                    generateAnnotationIfNotPresent(annotationDescriptorsAlreadyPresent, NotNull.class);
+                }
                 return;
             }
         }
@@ -198,6 +204,10 @@ public abstract class AnnotationCodegen {
 
         Class<?> annotationClass = isNullableType ? Nullable.class : NotNull.class;
 
+        generateAnnotationIfNotPresent(annotationDescriptorsAlreadyPresent, annotationClass);
+    }
+
+    private void generateAnnotationIfNotPresent(Set<String> annotationDescriptorsAlreadyPresent, Class<?> annotationClass) {
         String descriptor = Type.getType(annotationClass).getDescriptor();
         if (!annotationDescriptorsAlreadyPresent.contains(descriptor)) {
             visitAnnotation(descriptor, false).visitEnd();