unused symbol: should not apply to the public constructors of Externalizable classes (IDEA-120639 )

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/JavaHighlightUtil.java

@@ -27,13 +27,26 @@ import java.util.List;
 
 public class JavaHighlightUtil {
   public static boolean isSerializable(@NotNull PsiClass aClass) {
+    return isSerializable(aClass, "java.io.Serializable");
+  }
+
+  public static boolean isSerializable(@NotNull PsiClass aClass,
+                                       String serializableClassName) {
     Project project = aClass.getManager().getProject();
-    PsiClass serializableClass = JavaPsiFacade.getInstance(project).findClass("java.io.Serializable", aClass.getResolveScope());
+    PsiClass serializableClass = JavaPsiFacade.getInstance(project).findClass(serializableClassName, aClass.getResolveScope());
     return serializableClass != null && aClass.isInheritor(serializableClass, true);
   }
 
   public static boolean isSerializationRelatedMethod(PsiMethod method, PsiClass containingClass) {
-    if (containingClass == null || method.isConstructor()) return false;
+    if (containingClass == null) return false;
+    if (method.isConstructor()) {
+      if (isSerializable(containingClass, "java.io.Externalizable") && 
+          method.getParameterList().getParametersCount() == 0 &&
+          method.hasModifierProperty(PsiModifier.PUBLIC)) {
+        return true;
+      }
+      return false;
+    }
     if (method.hasModifierProperty(PsiModifier.STATIC)) return false;
     @NonNls String name = method.getName();
     PsiParameter[] parameters = method.getParameterList().getParameters();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting7/Externalizable.java

@@ -0,0 +1,36 @@
+import java.io.Externalizable;
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+
+class SerializationProxy implements Externalizable
+{
+  private static final long serialVersionUID = 1L;
+
+  private Object object;
+
+  public SerializationProxy()
+  {
+    // Empty constructor for Externalizable class
+  }
+
+  private <warning descr="Private constructor 'SerializationProxy(java.lang.Object)' is never used">SerializationProxy</warning>(Object object)
+  {
+    this.object = object;
+  }
+
+  public void writeExternal(ObjectOutput out) throws IOException
+  {
+    out.writeObject(this.object);
+  }
+
+  public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
+  {
+    this.object = in.readObject();
+  }
+
+  protected Object readResolve()
+  {
+    return this.object;
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingJdk7Test.java

@@ -180,4 +180,5 @@ public class LightAdvHighlightingJdk7Test extends LightDaemonAnalyzerTestCase {
   public void testIDEA78916() { doTest(false, false); }
   public void testIDEA111420() { doTest(false, false); }
   public void testIDEA111450() { doTest(true, false); }
+  public void testExternalizable() { doTest(true, false); }
 }