Fixing compilation

.idea/ant.xml

@@ -18,6 +18,14 @@
       <maximumStackSize value="2" />
       <properties />
     </buildFile>
+    <buildFile url="file://$PROJECT_DIR$/compiler/frontend/buildLexer.xml">
+      <additionalClassPath />
+      <antReference projectDefault="true" />
+      <customJdkName value="" />
+      <maximumHeapSize value="128" />
+      <maximumStackSize value="2" />
+      <properties />
+    </buildFile>
   </component>
 </project>
 

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetNullableType.java

@@ -2,6 +2,7 @@ package org.jetbrains.jet.lang.psi;
 
 import com.intellij.lang.ASTNode;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lexer.JetTokens;
 
 import java.util.List;
@@ -14,7 +15,7 @@ public class JetNullableType extends JetTypeElement {
         super(node);
     }
     
-    @NotNull
+    @Nullable
     public ASTNode getQuestionMarkNode() {
         return getNode().findChildByType(JetTokens.QUEST);
     }