Warn about annotations that targets non-existing accessors

#KT-15453 In Progress

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -250,6 +250,8 @@ public interface Errors {
     DiagnosticFactory1<KtAnnotationEntry, FqName> USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER = DiagnosticFactory1.create(WARNING);
     DiagnosticFactory1<KtAnnotationEntry, String> EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET = DiagnosticFactory1.create(ERROR);
 
+    DiagnosticFactory1<KtAnnotationEntry, String> ANNOTATION_TARGETS_NON_EXISTENT_ACCESSOR = DiagnosticFactory1.create(WARNING);
+
     // Const
     DiagnosticFactory0<PsiElement> CONST_VAL_NOT_TOP_LEVEL_OR_OBJECT = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<PsiElement> CONST_VAL_WITH_GETTER = DiagnosticFactory0.create(ERROR);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -154,6 +154,8 @@ public class DefaultErrorMessages {
         MAP.put(USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER, "Annotation ''{0}'' is not an experimental API marker, therefore its usage in @UseExperimental is ignored", TO_STRING);
         MAP.put(EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET, "Experimental annotation cannot be used on the following code elements: {0}. Please remove these targets", STRING);
 
+        MAP.put(ANNOTATION_TARGETS_NON_EXISTENT_ACCESSOR, "An accessor will not be generated for ''{0}'' so the annotation effectively has a ''SOURCE'' retention", STRING);
+
         MAP.put(REDUNDANT_MODIFIER, "Modifier ''{0}'' is redundant because ''{1}'' is present", TO_STRING, TO_STRING);
         MAP.put(REDUNDANT_OPEN_IN_INTERFACE, "Modifier 'open' is redundant for abstract interface members");
         MAP.put(REDUNDANT_MODIFIER_IN_GETTER, "Visibility modifiers are redundant in getter");