diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/psi/psiUtil/jetPsiUtil.kt b/compiler/frontend/src/org/jetbrains/jet/lang/psi/psiUtil/jetPsiUtil.kt
index 35aca069db8..bd04e0c8a2b 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/psi/psiUtil/jetPsiUtil.kt
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/psi/psiUtil/jetPsiUtil.kt
@@ -87,7 +87,7 @@ fun JetClassOrObject.effectiveDeclarations(): List<JetDeclaration> =
 fun JetClass.isAbstract() = isTrait() || hasModifier(JetTokens.ABSTRACT_KEYWORD)
 
 [suppress("UNCHECKED_CAST")]
-fun <T: PsiElement> PsiElement.replaced(newElement: T): T = replace(newElement)!! as T
+fun <T: PsiElement> PsiElement.replaced(newElement: T): T = replace(newElement) as T
 
 fun JetElement.blockExpressionsOrSingle(): Iterator<JetElement> =
         if (this is JetBlockExpression) getStatements().iterator() else SingleIterator(this)
diff --git a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallHierarchyNodeDescriptor.java b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallHierarchyNodeDescriptor.java
index 2cff620cb9c..9673c8a2ac9 100644
--- a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallHierarchyNodeDescriptor.java
+++ b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallHierarchyNodeDescriptor.java
@@ -58,7 +58,7 @@ public class KotlinCallHierarchyNodeDescriptor extends HierarchyNodeDescriptor i
 
     @Override
     public final boolean isValid(){
-        return myElement != null && myElement.isValid();
+        return myElement.isValid();
     }
 
     @Override
diff --git a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCalleeMethodsTreeStructure.java b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCalleeMethodsTreeStructure.java
index 19b5a99b3ce..615c352d08f 100644
--- a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCalleeMethodsTreeStructure.java
+++ b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCalleeMethodsTreeStructure.java
@@ -23,7 +23,6 @@ import com.intellij.openapi.project.Project;
 import com.intellij.psi.PsiClass;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiMethod;
-import com.intellij.util.ArrayUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.BindingContext;
@@ -93,8 +92,9 @@ public class KotlinCalleeMethodsTreeStructure extends KotlinCallTreeStructure {
         return result;
     }
 
+    @NotNull
     @Override
-    protected Object[] buildChildren(HierarchyNodeDescriptor descriptor) {
+    protected Object[] buildChildren(@NotNull HierarchyNodeDescriptor descriptor) {
         PsiElement targetElement = getTargetElement(descriptor);
 
         // Kotlin class constructor invoked from Java code
@@ -118,14 +118,10 @@ public class KotlinCalleeMethodsTreeStructure extends KotlinCallTreeStructure {
             return buildChildrenByKotlinTarget(descriptor, (JetElement) targetElement);
         }
 
-        if (javaTreeStructure != null) {
-            CallHierarchyNodeDescriptor javaDescriptor = descriptor instanceof CallHierarchyNodeDescriptor
-                                                         ? (CallHierarchyNodeDescriptor) descriptor
-                                                         : ((KotlinCallHierarchyNodeDescriptor)descriptor).getJavaDelegate();
-            return javaTreeStructure.getChildElements(javaDescriptor);
-        }
-
-        return ArrayUtil.EMPTY_OBJECT_ARRAY;
+        CallHierarchyNodeDescriptor javaDescriptor = descriptor instanceof CallHierarchyNodeDescriptor
+                                                     ? (CallHierarchyNodeDescriptor) descriptor
+                                                     : ((KotlinCallHierarchyNodeDescriptor)descriptor).getJavaDelegate();
+        return javaTreeStructure.getChildElements(javaDescriptor);
     }
 
     private Object[] buildChildrenByKotlinTarget(HierarchyNodeDescriptor descriptor, JetElement targetElement) {
diff --git a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallerMethodsTreeStructure.java b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallerMethodsTreeStructure.java
index cb3d2442c75..604c1f3b234 100644
--- a/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallerMethodsTreeStructure.java
+++ b/idea/src/org/jetbrains/jet/plugin/hierarchy/calls/KotlinCallerMethodsTreeStructure.java
@@ -57,8 +57,9 @@ public abstract class KotlinCallerMethodsTreeStructure extends KotlinCallTreeStr
             this.codeBlockForLocalDeclaration = codeBlockForLocalDeclaration;
         }
 
+        @NotNull
         @Override
-        protected Object[] buildChildren(HierarchyNodeDescriptor descriptor) {
+        protected Object[] buildChildren(@NotNull HierarchyNodeDescriptor descriptor) {
             final PsiElement element = getTargetElement(descriptor);
 
             BindingContext bindingContext =
@@ -97,8 +98,9 @@ public abstract class KotlinCallerMethodsTreeStructure extends KotlinCallTreeStr
             this.javaTreeStructure = new CallerMethodsTreeStructure(project, basePsiMethod, scopeType);
         }
 
+        @NotNull
         @Override
-        protected Object[] buildChildren(HierarchyNodeDescriptor descriptor) {
+        protected Object[] buildChildren(@NotNull HierarchyNodeDescriptor descriptor) {
             PsiElement element = getTargetElement(descriptor);
 
             SearchScope searchScope = getSearchScope(scopeType, basePsiClass);
@@ -106,7 +108,7 @@ public abstract class KotlinCallerMethodsTreeStructure extends KotlinCallTreeStr
                     new HashMap<PsiElement, HierarchyNodeDescriptor>();
 
             Object[] javaCallers = null;
-            if (element instanceof PsiMethod && javaTreeStructure != null) {
+            if (element instanceof PsiMethod) {
                 javaCallers = javaTreeStructure.getChildElements(getJavaNodeDescriptor(descriptor));
                 processPsiMethodCallers((PsiMethod) element, descriptor, methodToDescriptorMap, searchScope, true);
             }