diff --git a/idea/src/org/jetbrains/jet/lang/types/ClassDescriptor.java b/idea/src/org/jetbrains/jet/lang/types/ClassDescriptor.java
index 84faf016cec..18ca9a27ef9 100644
--- a/idea/src/org/jetbrains/jet/lang/types/ClassDescriptor.java
+++ b/idea/src/org/jetbrains/jet/lang/types/ClassDescriptor.java
@@ -14,7 +14,7 @@ public class ClassDescriptor extends MemberDescriptorImpl implements MemberDomai
 
     public ClassDescriptor(
             List<Annotation> annotations,
-            String name, List<TypeParameterDescriptor> typeParameters, Collection<Type> superclasses) {
+            String name, List<TypeParameterDescriptor> typeParameters, Collection<? extends Type> superclasses) {
         super(annotations, name);
         this.typeConstructor = new TypeConstructor(annotations, name, typeParameters, superclasses);
     }
diff --git a/idea/src/org/jetbrains/jet/lang/types/ClassType.java b/idea/src/org/jetbrains/jet/lang/types/ClassType.java
index 60fd0fe8909..6b04d349aa0 100644
--- a/idea/src/org/jetbrains/jet/lang/types/ClassType.java
+++ b/idea/src/org/jetbrains/jet/lang/types/ClassType.java
@@ -30,4 +30,9 @@ public class ClassType extends TypeImpl {
     public Collection<MemberDescriptor> getMembers() {
         throw new UnsupportedOperationException(); // TODO
     }
+
+    @Override
+    public <R, D> R accept(TypeVisitor<R, D> visitor, D data) {
+        return visitor.visitClassType(this, data);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/JetStandardClasses.java b/idea/src/org/jetbrains/jet/lang/types/JetStandardClasses.java
index 634841fd5f6..6c4b25783f5 100644
--- a/idea/src/org/jetbrains/jet/lang/types/JetStandardClasses.java
+++ b/idea/src/org/jetbrains/jet/lang/types/JetStandardClasses.java
@@ -1,6 +1,10 @@
 package org.jetbrains.jet.lang.types;
 
+import org.jetbrains.annotations.NotNull;
+
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.List;
 
 /**
  * @author abreslav
@@ -24,48 +28,91 @@ public class JetStandardClasses {
     private static final ClassDescriptor DOUBLE  = new ClassDescriptor("Double");
     private static final ClassDescriptor BOOLEAN = new ClassDescriptor("Boolean");
     private static final ClassDescriptor STRING  = new ClassDescriptor("String");
+    private static final ClassDescriptor UNIT    = new ClassDescriptor("Unit");
 
+    public static final int TUPLE_COUNT = 22;
+    private static final ClassDescriptor[] TUPLE = new ClassDescriptor[TUPLE_COUNT];
+    static {
+        for (int i = 0; i < TUPLE_COUNT; i++) {
+            List<TypeParameterDescriptor> parameters = new ArrayList<TypeParameterDescriptor>();
+            for (int j = 0; j < i; j++) {
+                parameters.add(new TypeParameterDescriptor(
+                        Collections.<Annotation>emptyList(),
+                        "T" + j,
+                        Variance.OUT_VARIANCE,
+                        Collections.<Type>emptySet()));
+            }
+            TUPLE[i] = new ClassDescriptor(
+                    Collections.<Annotation>emptyList(),
+                    "Tuple" + i,
+                    parameters,
+                    Collections.singleton(JetStandardClasses.getAnyType()));
+        }
+    }
+
+    @NotNull
     public static ClassDescriptor getAny() {
         return ANY;
     }
 
+    @NotNull
     public static ClassType getAnyType() {
         return ANY_TYPE;
     }
 
+    @NotNull
     public static ClassDescriptor getByte() {
         return BYTE;
     }
 
+    @NotNull
     public static ClassDescriptor getChar() {
         return CHAR;
     }
 
+    @NotNull
     public static ClassDescriptor getShort() {
         return SHORT;
     }
 
+    @NotNull
     public static ClassDescriptor getInt() {
         return INT;
     }
 
+    @NotNull
     public static ClassDescriptor getLong() {
         return LONG;
     }
 
+    @NotNull
     public static ClassDescriptor getFloat() {
         return FLOAT;
     }
 
+    @NotNull
     public static ClassDescriptor getDouble() {
         return DOUBLE;
     }
 
+    @NotNull
     public static ClassDescriptor getBoolean() {
         return BOOLEAN;
     }
 
+    @NotNull
     public static ClassDescriptor getString() {
         return STRING;
     }
+
+    @NotNull
+    public static ClassDescriptor getTuple(int size) {
+        return TUPLE[size];
+    }
+
+    @NotNull
+    public static ClassDescriptor getLabeledTuple(int size) {
+        // TODO
+        return getTuple(size);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java b/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
index 9607dbd5e0d..8940e51dcf0 100644
--- a/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
+++ b/idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java
@@ -6,7 +6,9 @@ import org.jetbrains.jet.JetNodeTypes;
 import org.jetbrains.jet.lang.psi.*;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * @author abreslav
@@ -74,10 +76,6 @@ public class JetTypeChecker {
         return checkSubtypeForTheSameConstructor(closestSupertype, supertype);
     }
 
-    private boolean checkSubtypeForTheSameConstructor(Type closestSupertype, Type supertype) {
-        throw new UnsupportedOperationException(); // TODO
-    }
-
     // This method returns the supertype of the first parameter that has the same constructor
     // as the second parameter, applying the substitution of type arguments to it
     @Nullable
@@ -89,10 +87,44 @@ public class JetTypeChecker {
         for (Type immediateSupertype : constructor.getSupertypes()) {
             Type correspondingSupertype = findCorrespondingSupertype(immediateSupertype, supertype);
             if (correspondingSupertype != null) {
-                return correspondingSupertype;
+                return substituteForParameters(subtype, correspondingSupertype);
             }
         }
         return null;
     }
 
+    private Type substituteForParameters(Type context, Type subject) {
+        Map<TypeParameterDescriptor, TypeProjection> parameterValues = new HashMap<TypeParameterDescriptor, TypeProjection>();
+
+        List<TypeParameterDescriptor> parameters = context.getConstructor().getParameters();
+        List<TypeProjection> contextArguments = context.getArguments();
+        for (int i = 0, parametersSize = parameters.size(); i < parametersSize; i++) {
+            TypeParameterDescriptor parameter = parameters.get(i);
+            TypeProjection value = contextArguments.get(i);
+            parameterValues.put(parameter, value);
+        }
+
+        return substitute(parameterValues, subject);
+    }
+
+    private Type substitute(Map<TypeParameterDescriptor, TypeProjection> parameterValues, Type subject) {
+        List<TypeProjection> newArguments = new ArrayList<TypeProjection>();
+        for (TypeProjection argument : subject.getArguments()) {
+            newArguments.add(new TypeProjection(argument.getProjection(), substitute(parameterValues, argument.getType())));
+        }
+        return specializeType(subject, newArguments);
+    }
+
+    private Type specializeType(Type type, List<TypeProjection> newArguments) {
+        // TODO
+        return type;
+    }
+
+    private boolean checkSubtypeForTheSameConstructor(Type subtype, Type supertype) {
+        assert subtype.getConstructor().equals(supertype.getConstructor());
+
+        // TODO
+        return true;
+    }
+
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/NothingType.java b/idea/src/org/jetbrains/jet/lang/types/NothingType.java
index 9659d8de8a3..7038502bf0b 100644
--- a/idea/src/org/jetbrains/jet/lang/types/NothingType.java
+++ b/idea/src/org/jetbrains/jet/lang/types/NothingType.java
@@ -38,4 +38,9 @@ public class NothingType extends TypeImpl {
     public Collection<MemberDescriptor> getMembers() {
         return Collections.emptySet();
     }
+
+    @Override
+    public <R, D> R accept(TypeVisitor<R, D> visitor, D data) {
+        return visitor.visitNothingType(this, data);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/ThisType.java b/idea/src/org/jetbrains/jet/lang/types/ThisType.java
index 8135e1ac977..bbf04dfc7f7 100644
--- a/idea/src/org/jetbrains/jet/lang/types/ThisType.java
+++ b/idea/src/org/jetbrains/jet/lang/types/ThisType.java
@@ -25,4 +25,9 @@ public class ThisType extends TypeImpl {
     public Collection<MemberDescriptor> getMembers() {
         throw new UnsupportedOperationException(); // TODO
     }
+
+    @Override
+    public <R, D> R accept(TypeVisitor<R, D> visitor, D data) {
+        return visitor.visitThisType(this, data);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/TupleType.java b/idea/src/org/jetbrains/jet/lang/types/TupleType.java
index 8af202b74a0..61a5922b741 100644
--- a/idea/src/org/jetbrains/jet/lang/types/TupleType.java
+++ b/idea/src/org/jetbrains/jet/lang/types/TupleType.java
@@ -10,29 +10,8 @@ import java.util.List;
  */
 public class TupleType extends TypeImpl {
 
-    public static final int TUPLE_COUNT = 22;
-    private static final TypeConstructor[] TUPLE = new TypeConstructor[TUPLE_COUNT];
-
     public static final TupleType UNIT = new TupleType(Collections.<Annotation>emptyList(), Collections.<Type>emptyList());
 
-    static {
-        for (int i = 0; i < TUPLE_COUNT; i++) {
-            List<TypeParameterDescriptor> parameters = new ArrayList<TypeParameterDescriptor>();
-            for (int j = 0; j < i; j++) {
-                parameters.add(new TypeParameterDescriptor(
-                        Collections.<Annotation>emptyList(),
-                        "T" + j,
-                        Variance.OUT_VARIANCE,
-                        Collections.<Type>emptySet()));
-            }
-            TUPLE[i] = new TypeConstructor(
-                    Collections.<Annotation>emptyList(),
-                    "Tuple" + i,
-                    parameters,
-                    Collections.singleton(JetStandardTypes.getAny()));
-        }
-    }
-
     public static TupleType getTupleType(List<Annotation> annotations, List<Type> arguments) {
         if (annotations.isEmpty() && arguments.isEmpty()) {
             return UNIT;
@@ -56,7 +35,7 @@ public class TupleType extends TypeImpl {
 
 
     private TupleType(List<Annotation> annotations, List<Type> arguments) {
-        super(annotations, TUPLE[arguments.size()], toProjections(arguments));
+        super(annotations, JetStandardClasses.getTuple(arguments.size()).getTypeConstructor(), toProjections(arguments));
     }
 
     @Override
@@ -64,6 +43,11 @@ public class TupleType extends TypeImpl {
         throw new UnsupportedOperationException("Not implemented"); // TODO
     }
 
+    @Override
+    public <R, D> R accept(TypeVisitor<R, D> visitor, D data) {
+        return visitor.visitTupleType(this, data);
+    }
+
     private static List<TypeProjection> toProjections(List<Type> arguments) {
         List<TypeProjection> result = new ArrayList<TypeProjection>();
         for (Type argument : arguments) {
diff --git a/idea/src/org/jetbrains/jet/lang/types/Type.java b/idea/src/org/jetbrains/jet/lang/types/Type.java
index 93faf98f626..25f5bc4d98d 100644
--- a/idea/src/org/jetbrains/jet/lang/types/Type.java
+++ b/idea/src/org/jetbrains/jet/lang/types/Type.java
@@ -11,4 +11,8 @@ public interface Type extends Annotated {
     List<TypeProjection> getArguments();
 
     Collection<MemberDescriptor> getMembers();
+
+    <R, D> R accept(TypeVisitor<R, D> visitor, D data);
+    <R> R acceptNoData(TypeVisitor<R, ?> visitor);
+    void acceptVoid(TypeVisitor<?, ?> visitor);
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/TypeConstructor.java b/idea/src/org/jetbrains/jet/lang/types/TypeConstructor.java
index 4577ec0c1f9..37fe781e77d 100644
--- a/idea/src/org/jetbrains/jet/lang/types/TypeConstructor.java
+++ b/idea/src/org/jetbrains/jet/lang/types/TypeConstructor.java
@@ -8,10 +8,10 @@ import java.util.List;
  */
 public class TypeConstructor extends AnnotatedImpl {
     private final List<TypeParameterDescriptor> parameters;
-    private final Collection<Type> supertypes;
+    private final Collection<? extends Type> supertypes;
     private final String debugName;
 
-    public TypeConstructor(List<Annotation> annotations, String debugName, List<TypeParameterDescriptor> parameters, Collection<Type> supertypes) {
+    public TypeConstructor(List<Annotation> annotations, String debugName, List<TypeParameterDescriptor> parameters, Collection<? extends Type> supertypes) {
         super(annotations);
         this.debugName = debugName;
         this.parameters = parameters;
@@ -22,7 +22,7 @@ public class TypeConstructor extends AnnotatedImpl {
         return parameters;
     }
 
-    public Collection<Type> getSupertypes() {
+    public Collection<? extends Type> getSupertypes() {
         return supertypes;
     }
 
diff --git a/idea/src/org/jetbrains/jet/lang/types/TypeImpl.java b/idea/src/org/jetbrains/jet/lang/types/TypeImpl.java
index 26bfec55684..4cf4e32eb86 100644
--- a/idea/src/org/jetbrains/jet/lang/types/TypeImpl.java
+++ b/idea/src/org/jetbrains/jet/lang/types/TypeImpl.java
@@ -43,4 +43,14 @@ public abstract class TypeImpl extends AnnotatedImpl implements Type {
         }
         return stringBuilder;
     }
+
+    @Override
+    public <R> R acceptNoData(TypeVisitor<R, ?> visitor) {
+        return accept(visitor, null);
+    }
+
+    @Override
+    public void acceptVoid(TypeVisitor<?, ?> visitor) {
+        accept(visitor, null);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/TypeVariable.java b/idea/src/org/jetbrains/jet/lang/types/TypeVariable.java
index 39f1bcac2ba..8061ba2f7cd 100644
--- a/idea/src/org/jetbrains/jet/lang/types/TypeVariable.java
+++ b/idea/src/org/jetbrains/jet/lang/types/TypeVariable.java
@@ -19,4 +19,9 @@ public class TypeVariable extends TypeImpl {
     public Collection<MemberDescriptor> getMembers() {
         throw new javax.help.UnsupportedOperationException(); // TODO
     }
+
+    @Override
+    public <R, D> R accept(TypeVisitor<R, D> visitor, D data) {
+        return visitor.visitTypeVariable(this, data);
+    }
 }
diff --git a/idea/src/org/jetbrains/jet/lang/types/TypeVisitor.java b/idea/src/org/jetbrains/jet/lang/types/TypeVisitor.java
new file mode 100644
index 00000000000..27f48335334
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/lang/types/TypeVisitor.java
@@ -0,0 +1,30 @@
+package org.jetbrains.jet.lang.types;
+
+/**
+ * @author abreslav
+ */
+public class TypeVisitor<R, D> {
+    public R visitNothingType(NothingType nothingType, D data) {
+        return visitType(nothingType, data);
+    }
+
+    public R visitTupleType(TupleType tupleType, D data) {
+        return visitType(tupleType, data);
+    }
+
+    public R visitTypeVariable(TypeVariable typeVariable, D data) {
+        return visitType(typeVariable, data);
+    }
+
+    public R visitClassType(ClassType classType, D data) {
+        return visitType(classType, data);
+    }
+
+    public R visitThisType(ThisType thisType, D data) {
+        return visitType(thisType, data);
+    }
+    
+    public R visitType(Type type, D data) {
+        throw new UnsupportedOperationException(); // TODO
+    }
+}
diff --git a/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java b/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
index 9b0b9db7488..d63b5f99fa4 100644
--- a/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
+++ b/idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java
@@ -10,6 +10,7 @@ import org.jetbrains.jet.lang.types.*;
 import org.jetbrains.jet.parsing.JetParsingTest;
 
 import java.io.File;
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -36,6 +37,10 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
                 return JetStandardClasses.getFloat();
             } else if ("Double".equals(name)) {
                 return JetStandardClasses.getDouble();
+            } else if ("Unit".equals(name)) {
+                return JetStandardClasses.getTuple(0);
+            } else if ("Any".equals(name)) {
+                return JetStandardClasses.getAny();
             }
             fail("Type not found: " + name);
             throw new IllegalStateException();
@@ -92,6 +97,17 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         assertSubtype("Double", "Double");
         assertSubtype("Unit", "Unit");
 
+        assertSubtype("Boolean", "Any");
+        assertSubtype("Byte", "Any");
+        assertSubtype("Char", "Any");
+        assertSubtype("Short", "Any");
+        assertSubtype("Int", "Any");
+        assertSubtype("Long", "Any");
+        assertSubtype("Float", "Any");
+        assertSubtype("Double", "Any");
+        assertSubtype("Unit", "Any");
+        assertSubtype("Any", "Any");
+
         assertNotSubtype("Boolean", "Byte");
         assertNotSubtype("Byte", "Short");
         assertNotSubtype("Char", "Int");
@@ -100,7 +116,7 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         assertNotSubtype("Long", "Double");
         assertNotSubtype("Float", "Double");
         assertNotSubtype("Double", "Int");
-        assertNotSubtype("Unit", "Unit");
+        assertNotSubtype("Unit", "Int");
 
         assertSubtype("(Boolean)", "(Boolean)");
         assertSubtype("(Byte)",    "(Byte)");
@@ -128,14 +144,21 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         boolean result = new JetTypeChecker().isSubtypeOf(
                 typeNode1,
                 typeNode2);
-        assertTrue(typeNode1 + " is not a subtype of " + typeNode2, result == expected);
+        String modifier = expected ? "not " : "";
+        assertTrue(typeNode1 + " is " + modifier + "a subtype of " + typeNode2, result == expected);
     }
 
     private Type toType(JetTypeReference typeNode) {
         List<JetAttribute> attributes = typeNode.getAttributes();
         JetTypeElement typeElement = typeNode.getTypeElement();
-        List<JetTypeReference> typeArguments = typeNode.getTypeArguments();
+        List<JetTypeReference> argumentElements = typeNode.getTypeArguments();
 
+        final List<Type> arguments = new ArrayList<Type>();
+        for (JetTypeReference argumentElement : argumentElements) {
+            arguments.add(toType(argumentElement));
+        }
+
+        // TODO annotations
         final Type[] result = new Type[1];
         typeElement.accept(new JetVisitor() {
             @Override
@@ -143,9 +166,15 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
                 result[0] = new ClassType(TypeResolver.INSTANCE.resolveClass(BASIC_SCOPE, type));
             }
 
+            @Override
+            public void visitTupleType(JetTupleType type) {
+                // TODO labels
+                result[0] = TupleType.getTupleType(arguments);
+            }
+
             @Override
             public void visitJetElement(JetElement elem) {
-                throw new IllegalArgumentException();
+                throw new IllegalArgumentException("Unsupported type: " + elem);
             }
         });