IDEA-86286 Java: bad completion (interface without package?)

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

@@ -46,12 +46,15 @@ public class InheritorsHolder implements Consumer<LookupElement> {
     if (object instanceof PsiClass) {
       final PsiClass psiClass = (PsiClass)object;
       if (JavaCompletionUtil.hasAccessibleInnerClass(psiClass, myPosition)) return;
-
-      ContainerUtil.addIfNotNull(myAddedClasses, getClassName(psiClass));
+      registerClass(psiClass);
     }
     myResult.addElement(AutoCompletionPolicy.NEVER_AUTOCOMPLETE.applyPolicy(lookupElement));
   }
 
+  public void registerClass(PsiClass psiClass) {
+    ContainerUtil.addIfNotNull(myAddedClasses, getClassName(psiClass));
+  }
+
   @Nullable
   private static String getClassName(PsiClass psiClass) {
     String name = psiClass.getQualifiedName();

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

@@ -225,11 +225,11 @@ public class JavaCompletionContributor extends CompletionContributor {
       return;
     }
 
+    final InheritorsHolder inheritors = new InheritorsHolder(position, result);
     if (JavaSmartCompletionContributor.IN_TYPE_ARGS.accepts(position)) {
-      new TypeArgumentCompletionProvider(false).addCompletions(parameters, new ProcessingContext(), result);
+      new TypeArgumentCompletionProvider(false, inheritors).addCompletions(parameters, new ProcessingContext(), result);
     }
 
-    final InheritorsHolder inheritors = new InheritorsHolder(position, result);
     if (JavaSmartCompletionContributor.AFTER_NEW.accepts(position)) {
       new JavaInheritorsGetter(ConstructorInsertHandler.BASIC_INSTANCE).generateVariants(parameters, result.getPrefixMatcher(), inheritors);
     }

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

@@ -286,7 +286,7 @@ public class JavaSmartCompletionContributor extends CompletionContributor {
       }
     });
 
-    extend(CompletionType.SMART, IN_TYPE_ARGS, new TypeArgumentCompletionProvider(true));
+    extend(CompletionType.SMART, IN_TYPE_ARGS, new TypeArgumentCompletionProvider(true, null));
 
 
     extend(CompletionType.SMART, AFTER_NEW, new JavaInheritorsGetter(ConstructorInsertHandler.SMART_INSTANCE));

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

@@ -47,9 +47,11 @@ import static com.intellij.patterns.PsiJavaPatterns.psiElement;
 */
 class TypeArgumentCompletionProvider extends CompletionProvider<CompletionParameters> {
   private final boolean mySmart;
+  @Nullable private final InheritorsHolder myInheritors;
 
-  TypeArgumentCompletionProvider(boolean smart) {
+  TypeArgumentCompletionProvider(boolean smart, @Nullable InheritorsHolder inheritors) {
     mySmart = smart;
+    myInheritors = inheritors;
   }
 
   protected void addCompletions(@NotNull final CompletionParameters parameters, final ProcessingContext processingContext, @NotNull final CompletionResultSet resultSet) {
@@ -71,7 +73,7 @@ class TypeArgumentCompletionProvider extends CompletionProvider<CompletionParame
     }
   }
 
-  private static void fillExpectedTypeArgs(CompletionResultSet resultSet,
+  private void fillExpectedTypeArgs(CompletionResultSet resultSet,
                                            PsiElement context,
                                            final PsiClass actualClass,
                                            final int index,
@@ -98,6 +100,14 @@ class TypeArgumentCompletionProvider extends CompletionProvider<CompletionParame
       typeItems.add(PsiTypeLookupItem.createLookupItem(arg, context));
     }
 
+    if (typeItems.size() == 1 && myInheritors != null) {
+      PsiClass aClass = PsiUtil.resolveClassInClassTypeOnly(typeItems.get(0).getPsiType());
+      if (aClass != null) {
+        JavaCompletionUtil.setShowFQN(typeItems.get(0));
+        myInheritors.registerClass(aClass);
+      }
+    }
+
     resultSet.addElement(new TypeArgsLookupElement(typeItems, globalTail, ConstructorInsertHandler.hasConstructorParameters(actualClass, context)));
   }
 
@@ -208,8 +218,10 @@ class TypeArgumentCompletionProvider extends CompletionProvider<CompletionParame
     public void renderElement(LookupElementPresentation presentation) {
       myTypeItems.get(0).renderElement(presentation);
       presentation.setItemText(getLookupString());
-      presentation.setTailText(null);
-      presentation.setTypeText(null);
+      if (myTypeItems.size() > 1) {
+        presentation.setTailText(null);
+        presentation.setTypeText(null);
+      }
     }
 
     @Override

java/java-tests/testData/codeInsight/completion/normal/DuplicateExpectedTypeInTypeArgumentList.java

@@ -0,0 +1,8 @@
+import java.util.*;
+import java.util.List;
+
+class Zoo {
+  {
+    List<String> l = new ArrayList<Stri<caret>>
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/NormalCompletionTest.groovy

@@ -1294,6 +1294,13 @@ public class ListUtils {
     assert !('return' in myFixture.lookupElementStrings)
   }
 
+  public void testDuplicateExpectedTypeInTypeArgumentList() {
+    configure()
+    def items = myFixture.lookupElements.findAll { it.lookupString == 'String' }
+    assert items.size() == 1
+    assert LookupElementPresentation.renderElement(items[0]).tailText?.contains('java.lang')
+  }
+
   public void testSameSignature() {
     configure()
     lookup.setCurrentItem(myItems[1])