Nullable and Nothing supported

idea/src/org/jetbrains/jet/lang/types/JetStandardClasses.java

@@ -8,12 +8,12 @@ import java.util.*;
  * @author abreslav
  */
 public class JetStandardClasses {
-    private static final TypeConstructor NOTHING = new TypeConstructor(
+
+    private static ClassDescriptor NOTHING_CLASS = new ClassDescriptor(
             Collections.<Attribute>emptyList(),
             "Nothing",
             Collections.<TypeParameterDescriptor>emptyList(),
             new AbstractCollection<Type>() {
-
                 @Override
                 public boolean contains(Object o) {
                     return o instanceof Type;
@@ -28,7 +28,8 @@ public class JetStandardClasses {
                 public int size() {
                     throw new UnsupportedOperationException();
                 }
-            });
+            }
+    );
 
     private static final ClassDescriptor ANY = new ClassDescriptor(
             Collections.<Attribute>emptyList(),
@@ -85,8 +86,13 @@ public class JetStandardClasses {
     private static final Type BOOLEAN_TYPE = new TypeImpl(getBoolean().getTypeConstructor(), STUB);
     private static final Type STRING_TYPE = new TypeImpl(getString().getTypeConstructor(), STUB);
     private static final Type UNIT_TYPE = new TypeImpl(getTuple(0).getTypeConstructor(), STUB);
-    private static final Type NOTHING_TYPE = new TypeImpl(NOTHING, STUB);
+    private static final Type NOTHING_TYPE = new TypeImpl(getNothing().getTypeConstructor(), STUB);
-    private static final Type NULLABLE_NOTHING_TYPE = new TypeImpl(Collections.<Attribute>emptyList(), NOTHING, true, Collections.<TypeProjection>emptyList(), TypeMemberDomain.EMPTY);
+    private static final Type NULLABLE_NOTHING_TYPE = new TypeImpl(
+            Collections.<Attribute>emptyList(),
+            getNothing().getTypeConstructor(),
+            true,
+            Collections.<TypeProjection>emptyList(),
+            TypeMemberDomain.EMPTY);
 
     @NotNull
     public static ClassDescriptor getAny() {
@@ -143,6 +149,11 @@ public class JetStandardClasses {
         return STRING;
     }
 
+    @NotNull
+    public static ClassDescriptor getNothing() {
+        return NOTHING_CLASS;
+    }
+
     @NotNull
     public static ClassDescriptor getTuple(int size) {
         return TUPLE[size];

idea/src/org/jetbrains/jet/lang/types/JetTypeChecker.java

@@ -75,6 +75,9 @@ public class JetTypeChecker {
         if (!supertype.isNullable() && subtype.isNullable()) {
             return false;
         }
+        if (subtype.getConstructor() == JetStandardClasses.getNothing().getTypeConstructor()) {
+            return true;
+        }
         @Nullable Type closestSupertype = findCorrespondingSupertype(subtype, supertype);
         if (closestSupertype == null) {
             return false;

idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java

@@ -177,6 +177,25 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         assertSubtype("Derived_T<Any>", "Base_T<in Int>");
     }
 
+    public void testNullable() throws Exception {
+        assertSubtype("Any?", "Any?");
+        assertSubtype("Any", "Any?");
+        assertNotSubtype("Any?", "Any");
+        assertSubtype("Int", "Any?");
+        assertSubtype("Int?", "Any?");
+        assertNotSubtype("Int?", "Any");
+    }
+
+    public void testNothing() throws Exception {
+        assertSubtype("Nothing", "Any");
+        assertSubtype("Nothing?", "Any?");
+        assertNotSubtype("Nothing?", "Any");
+
+        assertSubtype("Nothing", "Int");
+        assertSubtype("Nothing?", "Int?");
+        assertNotSubtype("Nothing?", "Int");
+    }
+
     public void testImplicitConversions() throws Exception {
         assertConvertibleTo("1", JetStandardClasses.getByteType());
     }
@@ -254,6 +273,8 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
                     return JetStandardClasses.getTuple(0);
                 } else if ("Any".equals(name)) {
                     return JetStandardClasses.getAny();
+                } else if ("Nothing".equals(name)) {
+                    return JetStandardClasses.getNothing();
                 }
                 if (CLASSES.isEmpty()) {
                     for (String classDeclaration : CLASS_DECLARATIONS) {