diff --git a/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java b/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
index 4c944b8afe6..30c82645c95 100644
--- a/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
+++ b/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
@@ -93,13 +93,13 @@ public class JetTypeChecker {
 
         Map<TypeConstructor, Set<JetType>> commonSupertypes = computeCommonRawSupertypes(typeSet);
         while (commonSupertypes.size() > 1) {
-            HashSet<JetType> merge = new HashSet<JetType>();
+            Set<JetType> merge = new HashSet<JetType>();
             for (Set<JetType> supertypes : commonSupertypes.values()) {
                 merge.addAll(supertypes);
             }
             commonSupertypes = computeCommonRawSupertypes(merge);
         }
-        assert !commonSupertypes.isEmpty() : commonSupertypes;
+        assert !commonSupertypes.isEmpty() : types;
         Map.Entry<TypeConstructor, Set<JetType>> entry = commonSupertypes.entrySet().iterator().next();
         JetType result = computeSupertypeProjections(entry.getKey(), entry.getValue());
 
@@ -413,4 +413,5 @@ public class JetTypeChecker {
         }
         return true;
     }
+
 }
\ No newline at end of file
diff --git a/idea/src/org/jetbrains/jet/lang/types/TypeUtils.java b/idea/src/org/jetbrains/jet/lang/types/TypeUtils.java
index 963c7757422..5066648eea5 100644
--- a/idea/src/org/jetbrains/jet/lang/types/TypeUtils.java
+++ b/idea/src/org/jetbrains/jet/lang/types/TypeUtils.java
@@ -1,5 +1,7 @@
 package org.jetbrains.jet.lang.types;
 
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.resolve.JetScope;
@@ -187,4 +189,35 @@ public class TypeUtils {
     public static TypeProjection makeStarProjection(@NotNull TypeParameterDescriptor parameterDescriptor) {
         return new TypeProjection(Variance.OUT_VARIANCE, parameterDescriptor.getBoundsAsType());
     }
+
+    private static void collectImmediateSupertypes(@NotNull JetType type, @NotNull Collection<JetType> result) {
+        TypeSubstitutor substitutor = TypeSubstitutor.create(type);
+        for (JetType supertype : type.getConstructor().getSupertypes()) {
+            result.add(substitutor.substitute(supertype, Variance.INVARIANT));
+        }
+    }
+
+    @NotNull
+    public static List<JetType> getImmediateSupertypes(@NotNull JetType type) {
+        List<JetType> result = Lists.newArrayList();
+        collectImmediateSupertypes(type, result);
+        return result;
+    }
+
+    private static void collectAllSupertypes(@NotNull JetType type, @NotNull Set<JetType> result) {
+        List<JetType> immediateSupertypes = getImmediateSupertypes(type);
+        result.addAll(immediateSupertypes);
+        for (JetType supertype : immediateSupertypes) {
+            collectAllSupertypes(supertype, result);
+        }
+    }
+
+    @NotNull
+    public static Set<JetType> getAllSupertypes(@NotNull JetType type) {
+        Set<JetType> result = Sets.newLinkedHashSet();
+        collectAllSupertypes(type, result);
+        return result;
+    }
+
+
 }
diff --git a/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java b/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
index 7eb350ed4af..bffb951936a 100644
--- a/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
+++ b/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
@@ -1,5 +1,6 @@
 package org.jetbrains.jet.types;
 
+import com.google.common.collect.Sets;
 import com.intellij.codeInsight.daemon.LightDaemonAnalyzerTestCase;
 import com.intellij.openapi.application.PathManager;
 import com.intellij.openapi.project.Project;
@@ -419,6 +420,24 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         assertType("new WithPredicate()?p", "WithPredicate?");
     }
 
+    public void testSupertypes() throws Exception {
+        assertSupertypes("DDerived1_T<Int>", "Derived_T<Int>", "Base_T<Int>", "Any");
+        assertSupertypes("DDerived2_T<Int>", "Derived_T<Int>", "Base_T<Int>", "Any");
+        assertSupertypes("Derived1_inT<Int>", "Derived_T<Int>", "Base_T<Int>", "Any", "Base_inT<Int>");
+    }
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    private void assertSupertypes(String typeStr, String... supertypeStrs) {
+        Set<JetType> allSupertypes = TypeUtils.getAllSupertypes(makeType(classDefinitions.BASIC_SCOPE, typeStr));
+        Set<JetType> expected = Sets.newHashSet();
+        for (String supertypeStr : supertypeStrs) {
+            JetType supertype = makeType(classDefinitions.BASIC_SCOPE, supertypeStr);
+            expected.add(supertype);
+        }
+        assertEquals(expected, allSupertypes);
+    }
+
     private void assertSubtype(String type1, String type2) {
         assertSubtypingRelation(type1, type2, true);
     }
@@ -509,8 +528,10 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
             "open class Derived_T<T> : Base_T<T>",
             "open class DDerived_T<T> : Derived_T<T>",
             "open class DDerived1_T<T> : Derived_T<T>",
+            "open class DDerived2_T<T> : Derived_T<T>, Base_T<T>",
             "open class Base_inT<in T>",
             "open class Derived_inT<in T> : Base_inT<T>",
+            "open class Derived1_inT<in T> : Base_inT<T>, Derived_T<T>",
             "open class Base_outT<out T>",
             "open class Derived_outT<out T> : Base_outT<T>",
             "class Properties { val p : Int }",