Synchronized is no more allowed on abstract functions

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/declarationCheckers.kt

@@ -143,6 +143,21 @@ public class VolatileAnnotationChecker : DeclarationChecker {
     }
 }
 
+public class SynchronizedAnnotationChecker : DeclarationChecker {
+
+    override fun check(declaration: JetDeclaration,
+                       descriptor: DeclarationDescriptor,
+                       diagnosticHolder: DiagnosticSink,
+                       bindingContext: BindingContext
+    ) {
+        val synchronizedAnnotation = DescriptorUtils.getSynchronizedAnnotation(descriptor)
+        if (synchronizedAnnotation != null && descriptor is FunctionDescriptor && descriptor.modality == Modality.ABSTRACT) {
+            val annotationEntry = DescriptorToSourceUtils.getSourceFromAnnotation(synchronizedAnnotation) ?: return
+            diagnosticHolder.report(ErrorsJvm.SYNCHRONIZED_ON_ABSTRACT.on(annotationEntry))
+        }
+    }
+}
+
 public class OverloadsAnnotationChecker: DeclarationChecker {
     override fun check(
             declaration: JetDeclaration,

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java

@@ -54,6 +54,7 @@ public class DefaultErrorMessagesJvm implements DefaultErrorMessages.Extension {
         MAP.put(ErrorsJvm.INAPPLICABLE_JVM_NAME, "''JvmName'' annotation is not applicable to this declaration");
         MAP.put(ErrorsJvm.ILLEGAL_JVM_NAME, "Illegal JVM name");
         MAP.put(ErrorsJvm.VOLATILE_ON_VALUE, "''Volatile'' annotation cannot be used on immutable properties");
+        MAP.put(ErrorsJvm.SYNCHRONIZED_ON_ABSTRACT, "''Synchronized'' annotation cannot be used on abstract functions");
         MAP.put(ErrorsJvm.EXTERNAL_DECLARATION_CANNOT_BE_ABSTRACT, "External declaration can not be abstract");
         MAP.put(ErrorsJvm.EXTERNAL_DECLARATION_CANNOT_HAVE_BODY, "External declaration can not have a body");
         MAP.put(ErrorsJvm.EXTERNAL_DECLARATION_IN_INTERFACE, "Members of interfaces can not be external");

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/ErrorsJvm.java

@@ -51,6 +51,7 @@ public interface ErrorsJvm {
     DiagnosticFactory1<JetAnnotationEntry, String> INAPPLICABLE_JVM_FIELD = DiagnosticFactory1.create(ERROR);
 
     DiagnosticFactory0<JetAnnotationEntry> VOLATILE_ON_VALUE = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<JetAnnotationEntry> SYNCHRONIZED_ON_ABSTRACT = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<JetDeclaration> OVERLOADS_WITHOUT_DEFAULT_ARGUMENTS = DiagnosticFactory0.create(WARNING, DECLARATION_SIGNATURE);
     DiagnosticFactory0<JetDeclaration> OVERLOADS_ABSTRACT = DiagnosticFactory0.create(ERROR, DECLARATION_SIGNATURE);

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/platform/JvmPlatformConfigurator.kt

@@ -32,6 +32,7 @@ public object JvmPlatformConfigurator : PlatformConfigurator(
                 PlatformStaticAnnotationChecker(),
                 JvmNameAnnotationChecker(),
                 VolatileAnnotationChecker(),
+                SynchronizedAnnotationChecker(),
                 LocalFunInlineChecker(),
                 ReifiedTypeParameterAnnotationChecker(),
                 NativeFunChecker(),