diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContext.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContext.java
index df52ff2bb47..474f094fb15 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContext.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContext.java
@@ -21,6 +21,7 @@ import com.intellij.psi.PsiElement;
 import jet.runtime.typeinfo.KotlinSignature;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.ReadOnly;
 import org.jetbrains.annotations.TestOnly;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
@@ -261,6 +262,7 @@ public interface BindingContext {
 
     // slice.isCollective() must be true
     @NotNull
+    @ReadOnly
     <K, V> Collection<K> getKeys(WritableSlice<K, V> slice);
 
     /** This method should be used only for debug and testing */
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/CompositeBindingContext.kt b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/CompositeBindingContext.kt
new file mode 100644
index 00000000000..47dbecadb23
--- /dev/null
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/CompositeBindingContext.kt
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2010-2014 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.resolve
+
+import org.jetbrains.jet.util.slicedmap.ReadOnlySlice
+import org.jetbrains.jet.util.slicedmap.WritableSlice
+import com.google.common.collect.ImmutableMap
+import org.jetbrains.jet.lang.diagnostics.Diagnostic
+import com.intellij.psi.PsiElement
+
+class CompositeBindingContext private (
+        private val delegates: List<BindingContext>
+) : BindingContext {
+
+    class object {
+        public fun create(delegates: List<BindingContext>): BindingContext {
+            if (delegates.isEmpty()) return BindingContext.EMPTY
+            if (delegates.size == 1) return delegates.first()
+            return CompositeBindingContext(delegates)
+        }
+    }
+
+    override fun <K, V> get(slice: ReadOnlySlice<K, V>?, key: K?): V? {
+        return delegates.stream().map { it[slice, key] }.firstOrNull { it != null }
+    }
+
+    override fun <K, V> getKeys(slice: WritableSlice<K, V>?): Collection<K> {
+        return delegates.flatMap { it.getKeys(slice) }
+    }
+
+    override fun <K, V> getSliceContents(slice: ReadOnlySlice<K, V>): ImmutableMap<K, V> {
+        val builder = ImmutableMap.builder<K, V>()!!
+        for (delegate in delegates) {
+            builder.putAll(delegate.getSliceContents(slice))
+        }
+        return builder.build()!!
+    }
+
+    override fun getDiagnostics(): Diagnostics {
+        return CompositeDiagnostics(delegates.map { it.getDiagnostics() })
+    }
+
+    private class CompositeDiagnostics(
+            private val delegates: List<Diagnostics>
+    ) : Diagnostics {
+        override fun iterator(): Iterator<Diagnostic> {
+            val emptyStream = listOf<Diagnostic>().stream()
+            return delegates.fold(emptyStream, { r, t -> r + t.stream()}).iterator()
+        }
+
+        override fun all(): Collection<Diagnostic> {
+            return delegates.flatMap { it.all() }
+        }
+
+        override fun forElement(psiElement: PsiElement): Collection<Diagnostic> {
+            return delegates.flatMap { it.forElement(psiElement) }
+        }
+
+        override fun isEmpty(): Boolean {
+            return delegates.all { it.isEmpty() }
+        }
+
+        override fun noSuppression(): Diagnostics {
+            return CompositeDiagnostics(delegates.map { it.noSuppression() })
+        }
+    }
+}