diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraints.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraints.java
index a8d8ea5d678..cbdd00a7f65 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraints.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraints.java
@@ -17,7 +17,6 @@
 package org.jetbrains.jet.lang.resolve.calls.inference;
 
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.Variance;
 
@@ -27,21 +26,17 @@ import java.util.Set;
  * @author svtk
  */
 public interface TypeConstraints {
-
-    @Nullable
-    JetType getLowerConstraint();
-
-    @Nullable
-    JetType getUpperConstraint();
+    @NotNull
+    Set<JetType> getLowerBounds();
 
     @NotNull
-    Set<JetType> getConflicts();
+    Set<JetType> getUpperBounds();
 
     @NotNull
-    Variance getVariance();
+    Set<JetType> getExactBounds();
 
-    boolean isSuccessful();
+    @NotNull
+    Variance getVarianceOfPosition();
 
     boolean isEmpty();
-
 }
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraintsImpl.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraintsImpl.java
index 62430383547..10e38d7030d 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraintsImpl.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeConstraintsImpl.java
@@ -16,160 +16,65 @@
 
 package org.jetbrains.jet.lang.resolve.calls.inference;
 
-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.descriptors.TypeParameterDescriptor;
-import org.jetbrains.jet.lang.types.CommonSupertypes;
 import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.Variance;
-import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
 
-import java.util.Collections;
 import java.util.Set;
 
 /**
  * @author svtk
  */
 public class TypeConstraintsImpl implements TypeConstraints {
-    private static final TypeConstraintsData EMPTY_CONSTRAINTS_DATA = new TypeConstraintsData(null, null, Collections.<JetType>emptySet());
-    private static class TypeConstraintsData {
-        private final JetType lowerConstraint;
-        private final JetType upperConstraint;
-        private final Set<JetType> conflicts;
+    private final Variance varianceOfPosition;
+    private final Set<JetType> upperBounds = Sets.newLinkedHashSet();
+    private final Set<JetType> lowerBounds = Sets.newLinkedHashSet();
+    private final Set<JetType> exactBounds = Sets.newLinkedHashSet();
 
-        private TypeConstraintsData(JetType lowerConstraint, JetType upperConstraint, Set<JetType> conflicts) {
-            this.lowerConstraint = lowerConstraint;
-            this.upperConstraint = upperConstraint;
-            this.conflicts = conflicts;
-        }
-
-        public JetType getLowerConstraint() {
-            return lowerConstraint;
-        }
-
-        public JetType getUpperConstraint() {
-            return upperConstraint;
-        }
-
-        public Set<JetType> getConflicts() {
-            return conflicts;
-        }
-    }
-
-    private final Variance variance;
-    private TypeConstraintsData typeConstraintsData = EMPTY_CONSTRAINTS_DATA;
-
-    private final Set<JetType> upperConstraints = Sets.newLinkedHashSet();
-    private final Set<JetType> lowerConstraints = Sets.newLinkedHashSet();
-    private final Set<JetType> equalConstraints = Sets.newLinkedHashSet();
-
-    private boolean changed = false;
-
-    public TypeConstraintsImpl(Variance variance) {
-        this.variance = variance;
+    public TypeConstraintsImpl(Variance varianceOfPosition) {
+        this.varianceOfPosition = varianceOfPosition;
     }
 
     @NotNull
     @Override
-    public Variance getVariance() {
-        return variance;
+    public Variance getVarianceOfPosition() {
+        return varianceOfPosition;
     }
 
-    public void addUpperConstraint(@NotNull JetType constraint) {
-        upperConstraints.add(constraint);
-        changed = true;
+    public void addUpperBound(@NotNull JetType type) {
+        upperBounds.add(type);
     }
 
-    public void addLowerConstraint(@NotNull JetType constraint) {
-        lowerConstraints.add(constraint);
-        changed = true;
+    public void addLowerBound(@NotNull JetType type) {
+        lowerBounds.add(type);
     }
 
-    public void addEqualConstraint(@NotNull JetType constraint) {
-        equalConstraints.add(constraint);
-        changed = true;
-    }
-
-    private void updateResult() {
-        if (!changed) {
-            return;
-        }
-        JetType lowerConstraint = null;
-        JetType upperConstraint = null;
-        Set<JetType> conflicts = Sets.newLinkedHashSet();
-        if (!lowerConstraints.isEmpty()) {
-            lowerConstraint = CommonSupertypes.commonSupertype(lowerConstraints);
-        }
-        if (!upperConstraints.isEmpty()) {
-            //todo
-            upperConstraint = upperConstraints.iterator().next();
-        }
-
-        if (lowerConstraint != null && upperConstraint != null && !JetTypeChecker.INSTANCE.isSubtypeOf(lowerConstraint, upperConstraint)) {
-            conflicts.add(lowerConstraint);
-            conflicts.add(upperConstraint);
-        }
-
-        if (equalConstraints.size() > 1) {
-            conflicts.addAll(equalConstraints);
-        }
-        else if (equalConstraints.size() == 1) {
-            JetType value = equalConstraints.iterator().next();
-            if (lowerConstraint != null && !JetTypeChecker.INSTANCE.isSubtypeOf(lowerConstraint, value)) {
-                conflicts.add(lowerConstraint);
-                conflicts.add(value);
-            }
-            if (upperConstraint != null && !JetTypeChecker.INSTANCE.isSubtypeOf(value, upperConstraint)) {
-                conflicts.add(upperConstraint);
-                conflicts.add(value);
-            }
-            lowerConstraint = value;
-            upperConstraint = value;
-        }
-        typeConstraintsData = new TypeConstraintsData(lowerConstraint, upperConstraint, conflicts);
-    }
-
-    @Override
-    public boolean isSuccessful() {
-        updateResult();
-        return typeConstraintsData.getConflicts().isEmpty();
-    }
-
-    @Nullable
-    @Override
-    public JetType getLowerConstraint() {
-        updateResult();
-        return typeConstraintsData.getLowerConstraint();
-    }
-
-    @Nullable
-    @Override
-    public JetType getUpperConstraint() {
-        updateResult();
-        return typeConstraintsData.getUpperConstraint();
-    }
-
-    @NotNull
-    @Override
-    public Set<JetType> getConflicts() {
-        updateResult();
-        return typeConstraintsData.getConflicts();
+    public void addExactBound(@NotNull JetType type) {
+        exactBounds.add(type);
     }
 
     @Override
     public boolean isEmpty() {
-        updateResult();
-        return typeConstraintsData.getLowerConstraint() == null && typeConstraintsData.getUpperConstraint() == null && typeConstraintsData.getConflicts().isEmpty();
+        return upperBounds.isEmpty() && lowerBounds.isEmpty() && exactBounds.isEmpty();
     }
 
+    @NotNull
     @Override
-    public String toString() {
-        return "TypeConstraints{" +
-               "upper=" + getUpperConstraint() +
-               ", lower=" + getLowerConstraint() +
-               ", conflicts=" + getConflicts() +
-               '}';
+    public Set<JetType> getLowerBounds() {
+        return lowerBounds;
+    }
+
+    @NotNull
+    @Override
+    public Set<JetType> getUpperBounds() {
+        return upperBounds;
+    }
+
+    @NotNull
+    @Override
+    public Set<JetType> getExactBounds() {
+        return exactBounds;
     }
 }