Smart completion includes object's from scope before searching for inheritors

#KT-6123 Fixed

idea/src/org/jetbrains/jet/plugin/completion/smart/SmartCompletion.kt

@@ -79,11 +79,18 @@ class SmartCompletion(val expression: JetSimpleNameExpression,
         val result = executeInternal() ?: return null
         // TODO: code could be more simple, see KT-5726
         val additionalItems = result.additionalItems.map(::postProcess)
+        val inheritanceSearcher = result.inheritanceSearcher?.let {
+            object : InheritanceItemsSearcher {
+                override fun search(nameFilter: (String) -> Boolean, consumer: (LookupElement) -> Unit) {
+                    it.search(nameFilter, { consumer(postProcess(it)) })
+                }
+            }
+        }
         val filter = result.declarationFilter
         return if (filter != null)
-            Result({ filter(it).map(::postProcess) }, additionalItems, result.inheritanceSearcher)
+            Result({ filter(it).map(::postProcess) }, additionalItems, inheritanceSearcher)
         else
-            Result(null, additionalItems, result.inheritanceSearcher)
+            Result(null, additionalItems, inheritanceSearcher)
     }
 
     private fun executeInternal(): Result? {

idea/src/org/jetbrains/jet/plugin/completion/smart/TypesWithSmartCasts.kt

@@ -62,7 +62,7 @@ class TypesWithSmartCasts(val bindingContext: BindingContext) {
                 }
                 return returnType.toList()
             }
-            else if (descriptor is ClassDescriptor && descriptor.getKind() == ClassKind.ENUM_ENTRY) {
+            else if (descriptor is ClassDescriptor && descriptor.getKind().isSingleton()) {
                 return listOf(descriptor.getDefaultType())
             }
             else {

idea/testData/completion/smart/Object.kt

@@ -0,0 +1,10 @@
+trait I
+
+object O : I
+
+fun foo(): I = <caret>
+
+// EXIST: { lookupString: "O", itemText: "O", tailText: " (<root>)" }
+// EXIST: foo
+// EXIST: object
+// NUMBER: 3

idea/testData/completion/smartMultiFile/NoObjectDuplication/Declarations.kt

@@ -0,0 +1,5 @@
+trait T
+
+object OO : T
+
+// ALLOW_AST_ACCESS

idea/testData/completion/smartMultiFile/NoObjectDuplication/NoObjectDuplication.kt

@@ -0,0 +1,6 @@
+fun foo(): T = <caret>
+
+// EXIST: foo
+// EXIST: { lookupString: "object", itemText: "object: T{...}" }
+// EXIST: { lookupString: "OO", itemText: "OO", tailText: " (<root>)" }
+// NUMBER: 3

idea/tests/org/jetbrains/jet/completion/JvmSmartCompletionTestGenerated.java

@@ -19,7 +19,6 @@ package org.jetbrains.jet.completion;
 import com.intellij.testFramework.TestDataPath;
 import org.jetbrains.jet.JUnit3RunnerWithInners;
 import org.jetbrains.jet.JetTestUtils;
-import org.jetbrains.jet.test.InnerTestClasses;
 import org.jetbrains.jet.test.TestMetadata;
 import org.junit.runner.RunWith;
 
@@ -624,6 +623,12 @@ public class JvmSmartCompletionTestGenerated extends AbstractJvmSmartCompletionT
         doTest(fileName);
     }
 
+    @TestMetadata("Object.kt")
+    public void testObject() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/smart/Object.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("ObjectsFromType.kt")
     public void testObjectsFromType() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/smart/ObjectsFromType.kt");

idea/tests/org/jetbrains/jet/completion/MultiFileSmartCompletionTestGenerated.java

@@ -77,4 +77,10 @@ public class MultiFileSmartCompletionTestGenerated extends AbstractMultiFileSmar
         String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/smartMultiFile/JavaStaticMethodArgument/");
         doTest(fileName);
     }
+
+    @TestMetadata("NoObjectDuplication")
+    public void testNoObjectDuplication() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/testData/completion/smartMultiFile/NoObjectDuplication/");
+        doTest(fileName);
+    }
 }

idea/tests/org/jetbrains/jet/completion/handlers/SmartCompletionHandlerTestGenerated.java

@@ -19,6 +19,7 @@ package org.jetbrains.jet.completion.handlers;
 import com.intellij.testFramework.TestDataPath;
 import org.jetbrains.jet.JUnit3RunnerWithInners;
 import org.jetbrains.jet.JetTestUtils;
+import org.jetbrains.jet.test.InnerTestClasses;
 import org.jetbrains.jet.test.TestMetadata;
 import org.junit.runner.RunWith;