diagnotics for invalid anchors to java classes (EA-72518 - assert: JavaPsiClassReferenceElement.getObject)

java/java-impl/src/com/intellij/codeInsight/completion/JavaPsiClassReferenceElement.java

@@ -99,8 +99,12 @@ public class JavaPsiClassReferenceElement extends LookupItem<Object> implements
         return psiClass;
       }
 
-      final PsiClass retrieve = (PsiClass)((PsiAnchor)myClass).retrieve();
-      assert retrieve != null : myQualifiedName;
+      PsiAnchor anchor = (PsiAnchor)myClass;
+      final PsiClass retrieve = (PsiClass)anchor.retrieve();
+      if (retrieve == null) {
+        throw new AssertionError(myQualifiedName + "; anchor=" + anchor + "; diagnostics=" +
+                                 (anchor instanceof PsiAnchor.StubIndexReference ? ((PsiAnchor.StubIndexReference)anchor).diagnoseNull() : null));
+      }
       myCache = new WeakReference<PsiClass>(retrieve);
       return retrieve;
     }

platform/core-impl/src/com/intellij/psi/WrappedElementAnchor.java

@@ -58,6 +58,6 @@ public class WrappedElementAnchor extends PsiAnchor {
 
   @Override
   public String toString() {
-    return "WrappedElementAnchor(" + myBaseAnchor.toString() + ")";
+    return "WrappedElementAnchor(" + myBaseAnchor + "; provider=" + myAnchorProvider + ")";
   }
 }