diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/AbstractNamespaceDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/AbstractNamespaceDescriptorImpl.java
index ea495607b24..97aeafbb5b2 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/AbstractNamespaceDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/AbstractNamespaceDescriptorImpl.java
@@ -27,7 +27,7 @@ import java.util.List;
 /**
  * @author abreslav
  */
-public abstract class AbstractNamespaceDescriptorImpl extends DeclarationDescriptorImpl implements NamespaceDescriptor {
+public abstract class AbstractNamespaceDescriptorImpl extends DeclarationDescriptorNonRootImpl implements NamespaceDescriptor {
     private NamespaceType namespaceType;
 
     public AbstractNamespaceDescriptorImpl(
@@ -44,6 +44,7 @@ public abstract class AbstractNamespaceDescriptorImpl extends DeclarationDescrip
     }
 
     @Override
+    @NotNull
     public NamespaceDescriptorParent getContainingDeclaration() {
         return (NamespaceDescriptorParent) super.getContainingDeclaration();
     }
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/CallableDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/CallableDescriptor.java
index 53100ad2694..eadb34b2156 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/CallableDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/CallableDescriptor.java
@@ -28,7 +28,7 @@ import java.util.Set;
 /**
 * @author abreslav
 */
-public interface CallableDescriptor extends DeclarationDescriptorWithVisibility {
+public interface CallableDescriptor extends DeclarationDescriptorWithVisibility, DeclarationDescriptorNonRoot {
     @NotNull
     ReceiverDescriptor getReceiverParameter();
 
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassDescriptorImpl.java
index 23bf950930e..837d71f6bc7 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassDescriptorImpl.java
@@ -32,7 +32,7 @@ import java.util.*;
 /**
  * @author abreslav
  */
-public class ClassDescriptorImpl extends DeclarationDescriptorImpl implements ClassDescriptorFromSource {
+public class ClassDescriptorImpl extends DeclarationDescriptorNonRootImpl implements ClassDescriptorFromSource {
     private TypeConstructor typeConstructor;
 
     private JetScope memberDeclarations;
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassOrNamespaceDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassOrNamespaceDescriptor.java
index 2c3ed9b09ed..78d21a88f8f 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassOrNamespaceDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassOrNamespaceDescriptor.java
@@ -19,5 +19,5 @@ package org.jetbrains.jet.lang.descriptors;
 /**
  * @author Stepan Koltsov
  */
-public interface ClassOrNamespaceDescriptor extends DeclarationDescriptor {
+public interface ClassOrNamespaceDescriptor extends DeclarationDescriptorNonRoot {
 }
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassifierDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassifierDescriptor.java
index f2b0db00f6b..519aaa4828d 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassifierDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ClassifierDescriptor.java
@@ -24,7 +24,7 @@ import org.jetbrains.jet.lang.types.TypeConstructor;
 /**
  * @author abreslav
  */
-public interface ClassifierDescriptor extends DeclarationDescriptor {
+public interface ClassifierDescriptor extends DeclarationDescriptorNonRoot {
     @NotNull
     TypeConstructor getTypeConstructor();
 
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorImpl.java
index 189b140577f..fe049778a17 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorImpl.java
@@ -17,7 +17,6 @@
 package org.jetbrains.jet.lang.descriptors;
 
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotatedImpl;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
 import org.jetbrains.jet.lang.resolve.name.Name;
@@ -26,19 +25,16 @@ import org.jetbrains.jet.resolve.DescriptorRenderer;
 import java.util.List;
 
 /**
- * @author abreslav
+ * @author Stepan Koltsov
  */
 public abstract class DeclarationDescriptorImpl extends AnnotatedImpl implements Named, DeclarationDescriptor {
 
     @NotNull
     private final Name name;
-    private final DeclarationDescriptor containingDeclaration;
 
-    public DeclarationDescriptorImpl(@Nullable DeclarationDescriptor containingDeclaration, @NotNull List<AnnotationDescriptor> annotations, @NotNull Name name) {
+    public DeclarationDescriptorImpl(@NotNull List<AnnotationDescriptor> annotations, @NotNull Name name) {
         super(annotations);
-
         this.name = name;
-        this.containingDeclaration = containingDeclaration;
     }
 
     @NotNull
@@ -53,11 +49,6 @@ public abstract class DeclarationDescriptorImpl extends AnnotatedImpl implements
         return this;
     }
 
-    @Override
-    public DeclarationDescriptor getContainingDeclaration() {
-        return containingDeclaration;
-    }
-
     @Override
     public void acceptVoid(DeclarationDescriptorVisitor<Void, Void> visitor) {
         accept(visitor, null);
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRoot.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRoot.java
new file mode 100644
index 00000000000..123019df146
--- /dev/null
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRoot.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2012 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.descriptors;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * @author Stepan Koltsov
+ */
+public interface DeclarationDescriptorNonRoot extends DeclarationDescriptor {
+
+    @Override
+    @NotNull
+    DeclarationDescriptor getContainingDeclaration();
+
+}
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRootImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRootImpl.java
new file mode 100644
index 00000000000..480cd02958f
--- /dev/null
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/DeclarationDescriptorNonRootImpl.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2010-2012 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.jet.lang.descriptors;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
+import org.jetbrains.jet.lang.resolve.name.Name;
+
+import java.util.List;
+
+/**
+ * @author abreslav
+ */
+public abstract class DeclarationDescriptorNonRootImpl
+        extends DeclarationDescriptorImpl
+        implements DeclarationDescriptorNonRoot {
+
+    @NotNull
+    private final DeclarationDescriptor containingDeclaration;
+
+    public DeclarationDescriptorNonRootImpl(
+            @NotNull DeclarationDescriptor containingDeclaration,
+            @NotNull List<AnnotationDescriptor> annotations,
+            @NotNull Name name) {
+        super(annotations, name);
+
+        this.containingDeclaration = containingDeclaration;
+    }
+
+    @Override
+    @NotNull
+    public DeclarationDescriptor getContainingDeclaration() {
+        return containingDeclaration;
+    }
+
+}
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/FunctionDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/FunctionDescriptorImpl.java
index f0df94e84be..a342dce8bcb 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/FunctionDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/FunctionDescriptorImpl.java
@@ -39,7 +39,7 @@ import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor
 /**
  * @author abreslav
  */
-public abstract class FunctionDescriptorImpl extends DeclarationDescriptorImpl implements FunctionDescriptor {
+public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRootImpl implements FunctionDescriptor {
 
     protected List<TypeParameterDescriptor> typeParameters;
     protected List<ValueParameterDescriptor> unsubstitutedValueParameters;
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/MemberDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/MemberDescriptor.java
index 76ceb86ca5e..6d694233955 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/MemberDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/MemberDescriptor.java
@@ -21,7 +21,7 @@ import org.jetbrains.annotations.NotNull;
 /**
  * @author abreslav
  */
-public interface MemberDescriptor extends DeclarationDescriptor, DeclarationDescriptorWithVisibility {
+public interface MemberDescriptor extends DeclarationDescriptorNonRoot, DeclarationDescriptorWithVisibility {
     @NotNull
     Modality getModality();
 
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ModuleDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ModuleDescriptor.java
index d483071fc2b..f7e51290833 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ModuleDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ModuleDescriptor.java
@@ -17,6 +17,7 @@
 package org.jetbrains.jet.lang.descriptors;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
 import org.jetbrains.jet.lang.resolve.name.Name;
 import org.jetbrains.jet.lang.types.TypeSubstitutor;
@@ -29,8 +30,8 @@ import java.util.Collections;
 public class ModuleDescriptor extends DeclarationDescriptorImpl implements ClassOrNamespaceDescriptor, NamespaceDescriptorParent {
     private NamespaceDescriptor rootNamepsace;
 
-    public ModuleDescriptor(Name name) {
-        super(null, Collections.<AnnotationDescriptor>emptyList(), name);
+    public ModuleDescriptor(@NotNull Name name) {
+        super(Collections.<AnnotationDescriptor>emptyList(), name);
         if (!name.isSpecial()) {
             throw new IllegalArgumentException("module name must be special: " + name);
         }
@@ -43,6 +44,12 @@ public class ModuleDescriptor extends DeclarationDescriptorImpl implements Class
         this.rootNamepsace = rootNs;
     }
 
+    @Override
+    @Nullable
+    public DeclarationDescriptor getContainingDeclaration() {
+        return null;
+    }
+
     public NamespaceDescriptor getRootNamespace() {
         return rootNamepsace;
     }
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/PropertyAccessorDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/PropertyAccessorDescriptor.java
index 844c47fbaa0..493ffbccaf4 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/PropertyAccessorDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/PropertyAccessorDescriptor.java
@@ -30,7 +30,7 @@ import java.util.Set;
 /**
  * @author abreslav
  */
-public abstract class PropertyAccessorDescriptor extends DeclarationDescriptorImpl implements FunctionDescriptor, MemberDescriptor {
+public abstract class PropertyAccessorDescriptor extends DeclarationDescriptorNonRootImpl implements FunctionDescriptor, MemberDescriptor {
 
     private final boolean hasBody;
     private final boolean isDefault;
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ScriptDescriptor.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ScriptDescriptor.java
index eb9ff460d60..bbc88078e17 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ScriptDescriptor.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/ScriptDescriptor.java
@@ -31,7 +31,7 @@ import java.util.List;
 /**
  * @author Stepan Koltsov
  */
-public class ScriptDescriptor extends DeclarationDescriptorImpl {
+public class ScriptDescriptor extends DeclarationDescriptorNonRootImpl {
     private static final Name NAME = Name.special("<script>");
 
     private final int priority;
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/TypeParameterDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/TypeParameterDescriptorImpl.java
index de949fcab80..ba84669b19b 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/TypeParameterDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/TypeParameterDescriptorImpl.java
@@ -35,7 +35,7 @@ import java.util.Set;
 /**
  * @author abreslav
  */
-public class TypeParameterDescriptorImpl extends DeclarationDescriptorImpl implements TypeParameterDescriptor {
+public class TypeParameterDescriptorImpl extends DeclarationDescriptorNonRootImpl implements TypeParameterDescriptor {
     public static TypeParameterDescriptor createWithDefaultBound(
             @NotNull DeclarationDescriptor containingDeclaration,
             @NotNull List<AnnotationDescriptor> annotations,
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/VariableDescriptorImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/VariableDescriptorImpl.java
index 4939698e41d..292928d4168 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/VariableDescriptorImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/descriptors/VariableDescriptorImpl.java
@@ -30,7 +30,7 @@ import java.util.Set;
 /**
  * @author abreslav
  */
-public abstract class VariableDescriptorImpl extends DeclarationDescriptorImpl implements VariableDescriptor {
+public abstract class VariableDescriptorImpl extends DeclarationDescriptorNonRootImpl implements VariableDescriptor {
     private JetType outType;
 
     public VariableDescriptorImpl(