diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/LockBasedStorageManager.java b/core/util.runtime/src/org/jetbrains/jet/storage/LockBasedStorageManager.java
index 0fa35abb0ea..fd63db91d0f 100644
--- a/core/util.runtime/src/org/jetbrains/jet/storage/LockBasedStorageManager.java
+++ b/core/util.runtime/src/org/jetbrains/jet/storage/LockBasedStorageManager.java
@@ -265,7 +265,7 @@ public class LockBasedStorageManager implements StorageManager {
 
         @Override
         @Nullable
-        public V invoke(@NotNull K input) {
+        public V invoke(K input) {
             Object value = cache.get(input);
             if (value != null) return WrappedValues.unescapeExceptionOrNull(value);
 
@@ -306,7 +306,7 @@ public class LockBasedStorageManager implements StorageManager {
 
         @NotNull
         @Override
-        public V invoke(@NotNull K input) {
+        public V invoke(K input) {
             V result = super.invoke(input);
             assert result != null : "compute() returned null";
             return result;
diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNotNull.java b/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNotNull.java
deleted file mode 100644
index 55e853f5640..00000000000
--- a/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNotNull.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright 2010-2013 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.storage;
-
-import jet.Function1;
-import org.jetbrains.annotations.NotNull;
-
-public interface MemoizedFunctionToNotNull<P, R> extends Function1<P, R> {
-    @Override
-    @NotNull
-    R invoke(P p);
-}
diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNullable.java b/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNullable.java
deleted file mode 100644
index 5521c143933..00000000000
--- a/core/util.runtime/src/org/jetbrains/jet/storage/MemoizedFunctionToNullable.java
+++ /dev/null
@@ -1,26 +0,0 @@
-/*
- * Copyright 2010-2013 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.storage;
-
-import jet.Function1;
-import org.jetbrains.annotations.Nullable;
-
-public interface MemoizedFunctionToNullable<P, R> extends Function1<P, R> {
-    @Override
-    @Nullable
-    R invoke(P p);
-}
diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/NullableLazyValue.java b/core/util.runtime/src/org/jetbrains/jet/storage/NullableLazyValue.java
deleted file mode 100644
index 63d3984c51a..00000000000
--- a/core/util.runtime/src/org/jetbrains/jet/storage/NullableLazyValue.java
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- * Copyright 2010-2013 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.storage;
-
-import jet.Function0;
-import org.jetbrains.annotations.Nullable;
-
-public interface NullableLazyValue<T> extends Function0<T> {
-    @Override
-    @Nullable
-    T invoke();
-
-    // Needed for proper toString() behaviors
-    boolean isComputed();
-}
diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/StorageManager.java b/core/util.runtime/src/org/jetbrains/jet/storage/StorageManager.java
index 4c37eb9e663..b0bcedd123d 100644
--- a/core/util.runtime/src/org/jetbrains/jet/storage/StorageManager.java
+++ b/core/util.runtime/src/org/jetbrains/jet/storage/StorageManager.java
@@ -19,6 +19,7 @@ package org.jetbrains.jet.storage;
 import jet.Function0;
 import jet.Function1;
 import jet.Unit;
+import jet.runtime.typeinfo.KotlinSignature;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -33,6 +34,8 @@ public interface StorageManager {
      */
     @NotNull
     <K, V> MemoizedFunctionToNotNull<K, V> createMemoizedFunction(@NotNull Function1<K, V> compute);
+    @KotlinSignature(
+            "fun <K, V> createMemoizedFunctionWithNullableValues(compute: (K) -> V?): MemoizedFunctionToNullable<K, V>")
     @NotNull
     <K, V> MemoizedFunctionToNullable<K, V> createMemoizedFunctionWithNullableValues(@NotNull Function1<K, V> compute);
 
diff --git a/core/util.runtime/src/org/jetbrains/jet/storage/NotNullLazyValue.java b/core/util.runtime/src/org/jetbrains/jet/storage/storage.kt
similarity index 58%
rename from core/util.runtime/src/org/jetbrains/jet/storage/NotNullLazyValue.java
rename to core/util.runtime/src/org/jetbrains/jet/storage/storage.kt
index ff0c0ef95d2..e6e0e2ff875 100644
--- a/core/util.runtime/src/org/jetbrains/jet/storage/NotNullLazyValue.java
+++ b/core/util.runtime/src/org/jetbrains/jet/storage/storage.kt
@@ -14,16 +14,17 @@
  * limitations under the License.
  */
 
-package org.jetbrains.jet.storage;
+package org.jetbrains.jet.storage
 
-import jet.Function0;
-import org.jetbrains.annotations.NotNull;
+public trait MemoizedFunctionToNotNull<P, R: Any> : Function1<P, R>
+public trait MemoizedFunctionToNullable<P, R: Any> : Function1<P, R?>
 
-public interface NotNullLazyValue<T> extends Function0<T> {
-    @Override
-    @NotNull
-    T invoke();
-
-    // Needed for proper toString() behaviors
-    boolean isComputed();
+public trait NotNullLazyValue<T: Any> : Function0<T> {
+    fun isComputed(): Boolean
 }
+
+public trait NullableLazyValue<T: Any> : Function0<T?> {
+    fun isComputed(): Boolean
+}
+
+fun <T> NotNullLazyValue<T>.get(_this: Any?, p: PropertyMetadata): T = invoke()
diff --git a/core/util.runtime/util.runtime.iml b/core/util.runtime/util.runtime.iml
index 4815fceb3bf..cd88404a500 100644
--- a/core/util.runtime/util.runtime.iml
+++ b/core/util.runtime/util.runtime.iml
@@ -9,6 +9,7 @@
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="library" exported="" scope="PROVIDED" name="intellij-core" level="project" />
     <orderEntry type="library" exported="" name="kotlin-runtime" level="project" />
+    <orderEntry type="library" name="annotations" level="project" />
   </component>
 </module>