3 files changed, 10 insertions, 2 deletions
diff --git a/src/com/google/doclava/ClassInfo.java b/src/com/google/doclava/ClassInfo.java
index a5ee7d4..8dde5c6 100644
--- a/src/com/google/doclava/ClassInfo.java
+++ b/src/com/google/doclava/ClassInfo.java
@@ -2092,9 +2092,12 @@ public class ClassInfo extends DocInfo implements ContainerInfo, Comparable, Sco
         /*
          * Similarly to the above, do not fail if this "new" method is really an override of an
          * existing superclass method.
+         * But we should fail if this is overriding an abstract method, because method's
+         * abstractness affects how users use it. See also Stubs.methodIsOverride().
          */
         MethodInfo mi = ClassInfo.overriddenMethod(mInfo, this);
-        if (mi == null) {
+        if (mi == null ||
+            mi.isAbstract() != mInfo.isAbstract()) {
           Errors.error(Errors.ADDED_METHOD, mInfo.position(), "Added public method "
               + mInfo.qualifiedName());
           consistent = false;
diff --git a/src/com/google/doclava/Errors.java b/src/com/google/doclava/Errors.java
index 84df16b..156de66 100644
--- a/src/com/google/doclava/Errors.java
+++ b/src/com/google/doclava/Errors.java
@@ -172,6 +172,7 @@ public class Errors {
   public static final Error INVALID_CONTENT_TYPE = new Error(119, ERROR);
   public static final Error INVALID_SAMPLE_INDEX = new Error(120, ERROR);
   public static final Error HIDDEN_TYPE_PARAMETER = new Error(121, HIDDEN);
+  public static final Error PRIVATE_SUPERCLASS = new Error(122, ERROR);
 
   public static final Error[] ERRORS =
       {UNRESOLVED_LINK, BAD_INCLUDE_TAG, UNKNOWN_TAG, UNKNOWN_PARAM_TAG_NAME,
@@ -183,7 +184,7 @@ public class Errors {
           CHANGED_TRANSIENT, CHANGED_VOLATILE, CHANGED_TYPE, CHANGED_VALUE, CHANGED_SUPERCLASS,
           CHANGED_SCOPE, CHANGED_ABSTRACT, CHANGED_THROWS, CHANGED_NATIVE, CHANGED_CLASS,
           CHANGED_DEPRECATED, CHANGED_SYNCHRONIZED, ADDED_FINAL_UNINSTANTIABLE, REMOVED_FINAL,
-          BROKEN_SINCE_FILE, INVALID_CONTENT_TYPE, HIDDEN_TYPE_PARAMETER};
+          BROKEN_SINCE_FILE, INVALID_CONTENT_TYPE, HIDDEN_TYPE_PARAMETER, PRIVATE_SUPERCLASS};
 
   public static boolean setErrorLevel(int code, int level) {
     for (Error e : ERRORS) {
diff --git a/src/com/google/doclava/Stubs.java b/src/com/google/doclava/Stubs.java
index bc5e586..44f1277 100644
--- a/src/com/google/doclava/Stubs.java
+++ b/src/com/google/doclava/Stubs.java
@@ -294,6 +294,10 @@ public class Stubs {
             + " stripped of unavailable superclass " + supr.qualifiedName());
       } else {
         cantStripThis(supr, notStrippable, "6:" + cl.realSuperclass().name() + cl.qualifiedName());
+        if (supr.isPrivate()) {
+          Errors.error(Errors.PRIVATE_SUPERCLASS, cl.position(), "Public class "
+              + cl.qualifiedName() + " extends private class " + supr.qualifiedName());
+        }
       }
     }
   }