diff --git a/idea/src/org/jetbrains/jet/lang/types/ConstructorDescriptorImpl.java b/idea/src/org/jetbrains/jet/lang/types/ConstructorDescriptorImpl.java
index a4c3280dcee..eff4db00ae9 100644
--- a/idea/src/org/jetbrains/jet/lang/types/ConstructorDescriptorImpl.java
+++ b/idea/src/org/jetbrains/jet/lang/types/ConstructorDescriptorImpl.java
@@ -29,7 +29,7 @@ public class ConstructorDescriptorImpl extends FunctionDescriptorImpl implements
     }
 
     public ConstructorDescriptor initialize(@NotNull List<ValueParameterDescriptor> unsubstitutedValueParameters) {
-        super.initialize(Collections.<TypeParameterDescriptor>emptyList(), unsubstitutedValueParameters, JetStandardClasses.getNothingType());
+        super.initialize(Collections.<TypeParameterDescriptor>emptyList(), unsubstitutedValueParameters, getContainingDeclaration().getDefaultType());
         return this;
     }
 
@@ -61,9 +61,11 @@ public class ConstructorDescriptorImpl extends FunctionDescriptorImpl implements
         return Collections.emptyList();
     }
 
-    @NotNull
     @Override
-    public JetType getUnsubstitutedReturnType() {
-        return getContainingDeclaration().getDefaultType();
+    protected FunctionDescriptorImpl createSubstitutedCopy() {
+        return new ConstructorDescriptorImpl(
+                this,
+                Collections.<Attribute>emptyList(), // TODO
+                isPrimary);
     }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorImpl.java b/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorImpl.java
index 4fb2f28a956..a3ad6e3c2a1 100644
--- a/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorImpl.java
+++ b/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorImpl.java
@@ -3,6 +3,7 @@ package org.jetbrains.jet.lang.types;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -78,8 +79,37 @@ public class FunctionDescriptorImpl extends DeclarationDescriptorImpl implements
     }
 
     @Override
-    public FunctionDescriptor substitute(TypeSubstitutor substitutor) {
-        return FunctionDescriptorUtil.substituteFunctionDescriptor(this, substitutor);
+    public final FunctionDescriptor substitute(TypeSubstitutor substitutor) {
+        if (substitutor.isEmpty()) {
+            return this;
+        }
+        FunctionDescriptorImpl substitutedDescriptor;
+        substitutedDescriptor = createSubstitutedCopy();
+
+        List<ValueParameterDescriptor> substitutedValueParameters = FunctionDescriptorUtil.getSubstitutedValueParameters(substitutedDescriptor, this, substitutor);
+        if (substitutedValueParameters == null) {
+            return null;
+        }
+
+        JetType substitutedReturnType = FunctionDescriptorUtil.getSubstitutedReturnType(this, substitutor);
+        if (substitutedReturnType == null) {
+            return null;
+        }
+
+        substitutedDescriptor.initialize(
+                Collections.<TypeParameterDescriptor>emptyList(), // TODO : questionable
+                substitutedValueParameters,
+                substitutedReturnType
+        );
+        return substitutedDescriptor;
+    }
+
+    protected FunctionDescriptorImpl createSubstitutedCopy() {
+        return new FunctionDescriptorImpl(
+                this,
+                // TODO : safeSubstitute
+                getAttributes(),
+                getName());
     }
 
     @Override
diff --git a/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorUtil.java b/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorUtil.java
index ea98c11c019..19b0dace901 100644
--- a/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorUtil.java
+++ b/idea/src/org/jetbrains/jet/lang/types/FunctionDescriptorUtil.java
@@ -58,7 +58,7 @@ public class FunctionDescriptorUtil {
     }
 
     @Nullable
-    private static List<ValueParameterDescriptor> getSubstitutedValueParameters(FunctionDescriptor substitutedDescriptor, @NotNull FunctionDescriptor functionDescriptor, TypeSubstitutor substitutor) {
+    public static List<ValueParameterDescriptor> getSubstitutedValueParameters(FunctionDescriptor substitutedDescriptor, @NotNull FunctionDescriptor functionDescriptor, TypeSubstitutor substitutor) {
         List<ValueParameterDescriptor> result = new ArrayList<ValueParameterDescriptor>();
         List<ValueParameterDescriptor> unsubstitutedValueParameters = functionDescriptor.getUnsubstitutedValueParameters();
         for (int i = 0, unsubstitutedValueParametersSize = unsubstitutedValueParameters.size(); i < unsubstitutedValueParametersSize; i++) {
@@ -81,53 +81,14 @@ public class FunctionDescriptorUtil {
     }
 
     @Nullable
-    private static JetType getSubstitutedReturnType(@NotNull FunctionDescriptor functionDescriptor, TypeSubstitutor substitutor) {
+    public static JetType getSubstitutedReturnType(@NotNull FunctionDescriptor functionDescriptor, TypeSubstitutor substitutor) {
         return substitutor.substitute(functionDescriptor.getUnsubstitutedReturnType(), Variance.OUT_VARIANCE);
     }
 
     @Nullable
     public static FunctionDescriptor substituteFunctionDescriptor(@NotNull List<JetType> typeArguments, @NotNull FunctionDescriptor functionDescriptor) {
         Map<TypeConstructor, TypeProjection> substitutionContext = createSubstitutionContext(functionDescriptor, typeArguments);
-        return substituteFunctionDescriptor(functionDescriptor, TypeSubstitutor.create(substitutionContext));
-    }
-
-    @Nullable
-    public static FunctionDescriptor substituteFunctionDescriptor(FunctionDescriptor functionDescriptor, TypeSubstitutor substitutor) {
-        if (substitutor.isEmpty()) {
-            return functionDescriptor;
-        }
-        FunctionDescriptorImpl substitutedDescriptor;
-        if (functionDescriptor instanceof ConstructorDescriptor) {
-            ConstructorDescriptor original = (ConstructorDescriptor) functionDescriptor;
-
-            substitutedDescriptor = new ConstructorDescriptorImpl(
-                   original, functionDescriptor.getAttributes(), original.isPrimary()
-            );
-        }
-        else {
-            substitutedDescriptor = new FunctionDescriptorImpl(
-                    functionDescriptor,
-                    // TODO : safeSubstitute
-                    functionDescriptor.getAttributes(),
-                    functionDescriptor.getName());
-        }
-
-        List<ValueParameterDescriptor> substitutedValueParameters = getSubstitutedValueParameters(substitutedDescriptor, functionDescriptor, substitutor);
-        if (substitutedValueParameters == null) {
-            return null;
-        }
-
-        JetType substitutedReturnType = getSubstitutedReturnType(functionDescriptor, substitutor);
-        if (substitutedReturnType == null) {
-            return null;
-        }
-
-        substitutedDescriptor.initialize(
-                Collections.<TypeParameterDescriptor>emptyList(), // TODO : questionable
-                substitutedValueParameters,
-                substitutedReturnType
-        );
-        return substitutedDescriptor;
+        return functionDescriptor.substitute(TypeSubstitutor.create(substitutionContext));
     }
 
     @NotNull