JVM, JVM IR: report error if not all parts of multifile class are @JvmSynthetic

#KT-41884 Fixed

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

@@ -78,6 +78,7 @@ public class DefaultErrorMessagesJvm implements DefaultErrorMessages.Extension {
         MAP.put(JVM_PACKAGE_NAME_NOT_SUPPORTED_IN_FILES_WITH_CLASSES, "''@JvmPackageName'' annotation is not supported for files with class declarations");
 
         MAP.put(STATE_IN_MULTIFILE_CLASS, "Non-const property with backing field or delegate is not allowed in a multi-file class if -Xmultifile-parts-inherit is enabled");
+        MAP.put(NOT_ALL_MULTIFILE_CLASS_PARTS_ARE_JVM_SYNTHETIC, "All of multi-file class parts should be annotated with @JvmSynthetic if at least one of them is");
 
         MAP.put(NO_REFLECTION_IN_CLASS_PATH, "Call uses reflection API which is not found in compilation classpath. " +
                                              "Make sure you have kotlin-reflect.jar in the classpath");

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

@@ -74,6 +74,7 @@ public interface ErrorsJvm {
     DiagnosticFactory0<KtAnnotationEntry> JVM_PACKAGE_NAME_NOT_SUPPORTED_IN_FILES_WITH_CLASSES = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<KtDeclaration> STATE_IN_MULTIFILE_CLASS = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<PsiElement> NOT_ALL_MULTIFILE_CLASS_PARTS_ARE_JVM_SYNTHETIC = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<PsiElement> INTERFACE_CANT_CALL_DEFAULT_METHOD_VIA_SUPER = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<PsiElement> SUBCLASS_CANT_CALL_COMPANION_PROTECTED_NON_STATIC = DiagnosticFactory0.create(ERROR);