diff --git a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpBackrefImpl.java b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpBackrefImpl.java
index 5aa03c2cac45..63bad0e924d7 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpBackrefImpl.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpBackrefImpl.java
@@ -104,6 +104,7 @@ public class RegExpBackrefImpl extends RegExpElementImpl implements RegExpBackre
                 return RegExpBackrefImpl.this.resolve();
             }
             
+            @NotNull
             public Object[] getVariants() {
                 return ArrayUtil.EMPTY_OBJECT_ARRAY;
             }
diff --git a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpPropertyImpl.java b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpPropertyImpl.java
index b4b9cfe87dd1..8f58881c7f96 100644
--- a/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpPropertyImpl.java
+++ b/RegExpSupport/src/org/intellij/lang/regexp/psi/impl/RegExpPropertyImpl.java
@@ -118,6 +118,7 @@ public class RegExpPropertyImpl extends RegExpElementImpl implements RegExpPrope
             return false;
         }
 
+        @NotNull
         public Object[] getVariants() {
             final ASTNode categoryNode = getCategoryNode();
             if (categoryNode != null && categoryNode.getText().startsWith("In") && !categoryNode.getText().startsWith("Intelli")) {
diff --git a/java/compiler/impl/src/com/intellij/compiler/impl/CompileContextExProxy.java b/java/compiler/impl/src/com/intellij/compiler/impl/CompileContextExProxy.java
index e312ca89abe2..5e45940a6e00 100644
--- a/java/compiler/impl/src/com/intellij/compiler/impl/CompileContextExProxy.java
+++ b/java/compiler/impl/src/com/intellij/compiler/impl/CompileContextExProxy.java
@@ -141,11 +141,11 @@ public class CompileContextExProxy implements CompileContextEx {
     return myDelegate.isRebuild();
   }
 
-  public <T> T getUserData(final Key<T> key) {
+  public <T> T getUserData(@NotNull final Key<T> key) {
     return myDelegate.getUserData(key);
   }
 
-  public <T> void putUserData(final Key<T> key, final T value) {
+  public <T> void putUserData(@NotNull final Key<T> key, final T value) {
     myDelegate.putUserData(key, value);
   }
 
diff --git a/java/compiler/impl/src/com/intellij/compiler/impl/CompositeScope.java b/java/compiler/impl/src/com/intellij/compiler/impl/CompositeScope.java
index 3f15c8af5ab3..2b8195fbe556 100644
--- a/java/compiler/impl/src/com/intellij/compiler/impl/CompositeScope.java
+++ b/java/compiler/impl/src/com/intellij/compiler/impl/CompositeScope.java
@@ -89,7 +89,7 @@ public class CompositeScope extends UserDataHolderBase implements CompileScope{
     return modules.toArray(new Module[modules.size()]);
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     for (CompileScope compileScope : myScopes) {
       T userData = compileScope.getUserData(key);
       if (userData != null) {
diff --git a/java/compiler/impl/src/com/intellij/compiler/impl/TrackDependenciesScope.java b/java/compiler/impl/src/com/intellij/compiler/impl/TrackDependenciesScope.java
index 00a37258adf8..a26e5a50ed40 100644
--- a/java/compiler/impl/src/com/intellij/compiler/impl/TrackDependenciesScope.java
+++ b/java/compiler/impl/src/com/intellij/compiler/impl/TrackDependenciesScope.java
@@ -66,7 +66,7 @@ public class TrackDependenciesScope extends UserDataHolderBase implements Compil
     }
   }
 
-  public <T> T getUserData(final Key<T> key) {
+  public <T> T getUserData(@NotNull final Key<T> key) {
     T userData = myDelegate.getUserData(key);
     if (userData != null) {
       return userData;
diff --git a/java/compiler/openapi/src/com/intellij/openapi/compiler/DummyCompileContext.java b/java/compiler/openapi/src/com/intellij/openapi/compiler/DummyCompileContext.java
index 82f02dc6bb91..4a42a17d2966 100644
--- a/java/compiler/openapi/src/com/intellij/openapi/compiler/DummyCompileContext.java
+++ b/java/compiler/openapi/src/com/intellij/openapi/compiler/DummyCompileContext.java
@@ -24,6 +24,7 @@ import com.intellij.openapi.util.Computable;
 import com.intellij.openapi.util.Key;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.pom.Navigatable;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public class DummyCompileContext implements CompileContext {
@@ -99,11 +100,11 @@ public class DummyCompileContext implements CompileContext {
     return null;
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     return null;
   }
 
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
   }
 
   public boolean isMake() {
@@ -113,4 +114,4 @@ public class DummyCompileContext implements CompileContext {
   public boolean isRebuild() {
     return false;
   }
-}
\ No newline at end of file
+}
diff --git a/java/idea-ui/src/com/intellij/facet/impl/ui/FacetEditorContextBase.java b/java/idea-ui/src/com/intellij/facet/impl/ui/FacetEditorContextBase.java
index c54f96d755c0..ac4e67d51576 100644
--- a/java/idea-ui/src/com/intellij/facet/impl/ui/FacetEditorContextBase.java
+++ b/java/idea-ui/src/com/intellij/facet/impl/ui/FacetEditorContextBase.java
@@ -98,7 +98,7 @@ public abstract class FacetEditorContextBase extends UserDataHolderBase implemen
   public abstract ArtifactsStructureConfigurableContext getArtifactsStructureContext();
 
   @Nullable
-  public <T> T getUserData(final Key<T> key) {
+  public <T> T getUserData(@NotNull final Key<T> key) {
     T t = super.getUserData(key);
     if (t == null && myParentContext != null) {
       t = myParentContext.getUserData(key);
diff --git a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsJavaCodeReferenceElementImpl.java b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsJavaCodeReferenceElementImpl.java
index 5708a5780715..57adfbf23042 100644
--- a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsJavaCodeReferenceElementImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsJavaCodeReferenceElementImpl.java
@@ -206,6 +206,7 @@ public class ClsJavaCodeReferenceElementImpl extends ClsElementImpl implements P
            || getManager().areElementsEquivalent(resolve(), element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for references to compiled code");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsReferenceExpressionImpl.java b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsReferenceExpressionImpl.java
index 61c128e1d647..2983154903b6 100644
--- a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsReferenceExpressionImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsReferenceExpressionImpl.java
@@ -145,6 +145,7 @@ public class ClsReferenceExpressionImpl extends ClsElementImpl implements PsiRef
     return myPatternExpression.isReferenceTo(element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     return myPatternExpression.getVariants();
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsTypeParameterReferenceImpl.java b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsTypeParameterReferenceImpl.java
index e1c42bb22e73..2c9c154b800c 100644
--- a/java/java-impl/src/com/intellij/psi/impl/compiled/ClsTypeParameterReferenceImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/compiled/ClsTypeParameterReferenceImpl.java
@@ -146,6 +146,7 @@ public class ClsTypeParameterReferenceImpl extends ClsElementImpl implements Psi
     throw new IncorrectOperationException(CAN_NOT_MODIFY_MESSAGE);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for references to compiled code");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/light/LightClassReference.java b/java/java-impl/src/com/intellij/psi/impl/light/LightClassReference.java
index bbfba0ba65eb..ec5f6e4f8a13 100644
--- a/java/java-impl/src/com/intellij/psi/impl/light/LightClassReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/light/LightClassReference.java
@@ -228,6 +228,7 @@ public class LightClassReference extends LightElement implements PsiJavaCodeRefe
     return getManager().areElementsEquivalent(resolve(), element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for light references");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/light/LightClassReferenceExpression.java b/java/java-impl/src/com/intellij/psi/impl/light/LightClassReferenceExpression.java
index 9baa3097148a..add6df030299 100644
--- a/java/java-impl/src/com/intellij/psi/impl/light/LightClassReferenceExpression.java
+++ b/java/java-impl/src/com/intellij/psi/impl/light/LightClassReferenceExpression.java
@@ -48,6 +48,7 @@ public class LightClassReferenceExpression extends LightClassReference implement
     return getManager().areElementsEquivalent(resolve(), element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for light references");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/light/LightMemberReference.java b/java/java-impl/src/com/intellij/psi/impl/light/LightMemberReference.java
index 898718bffa88..b02a2c66fb82 100644
--- a/java/java-impl/src/com/intellij/psi/impl/light/LightMemberReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/light/LightMemberReference.java
@@ -144,6 +144,7 @@ public class LightMemberReference extends LightElement implements PsiJavaCodeRef
     return element instanceof PsiClass && element.getManager().areElementsEquivalent(resolve(), element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for light references");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/light/LightPackageReference.java b/java/java-impl/src/com/intellij/psi/impl/light/LightPackageReference.java
index 3c7d906efde6..c6b7e8c8a42d 100644
--- a/java/java-impl/src/com/intellij/psi/impl/light/LightPackageReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/light/LightPackageReference.java
@@ -114,6 +114,7 @@ public class LightPackageReference extends LightElement implements PsiJavaCodeRe
     return getManager().areElementsEquivalent(resolve(), element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     throw new RuntimeException("Variants are not available for light references");
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/PsiEnumConstantImpl.java b/java/java-impl/src/com/intellij/psi/impl/source/PsiEnumConstantImpl.java
index 958702a46928..75796c8dd24f 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/PsiEnumConstantImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/PsiEnumConstantImpl.java
@@ -202,6 +202,7 @@ public class PsiEnumConstantImpl extends JavaStubPsiElement<PsiFieldStub> implem
       throw new IncorrectOperationException("Invalid operation");
     }
 
+    @NotNull
     public Object[] getVariants() {
       return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/PsiImportStaticReferenceElementImpl.java b/java/java-impl/src/com/intellij/psi/impl/source/PsiImportStaticReferenceElementImpl.java
index a61ed6a614ba..1528fd1b25dc 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/PsiImportStaticReferenceElementImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/PsiImportStaticReferenceElementImpl.java
@@ -383,6 +383,7 @@ public class PsiImportStaticReferenceElementImpl extends CompositePsiElement imp
     PsiScopesUtil.resolveAndWalk(proc, this, null, true);
   }
 
+  @NotNull
   public Object[] getVariants() {
     // IMPLEMENT[dsl]
     return ArrayUtil.EMPTY_OBJECT_ARRAY;
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/PsiJavaCodeReferenceElementImpl.java b/java/java-impl/src/com/intellij/psi/impl/source/PsiJavaCodeReferenceElementImpl.java
index 2ce9002a3470..1d6aff6e3c01 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/PsiJavaCodeReferenceElementImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/PsiJavaCodeReferenceElementImpl.java
@@ -694,6 +694,7 @@ public class PsiJavaCodeReferenceElementImpl extends CompositePsiElement impleme
     myCachedTextSkipWhiteSpaceAndComments = null;
   }
 
+  @NotNull
   public Object[] getVariants() {
     final ElementFilter filter;
     switch (getKind()) {
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/PsiLabelReference.java b/java/java-impl/src/com/intellij/psi/impl/source/PsiLabelReference.java
index c18ec0be8e82..fe1dac35655c 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/PsiLabelReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/PsiLabelReference.java
@@ -86,6 +86,7 @@ public class PsiLabelReference implements PsiReference{
       return resolve() == element;
     }
 
+    @NotNull
     public Object[] getVariants(){
       final List result = new ArrayList();
       PsiElement context = myStatement;
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocMethodOrFieldRef.java b/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocMethodOrFieldRef.java
index 0798658ad3c3..350ee4ee1644 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocMethodOrFieldRef.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocMethodOrFieldRef.java
@@ -116,6 +116,7 @@ public class PsiDocMethodOrFieldRef extends CompositePsiElement implements PsiDo
         }
 
         return new MyReference(method) {
+          @NotNull
           public PsiElement[] getVariants() {
             final List<PsiMethod> lst = new ArrayList<PsiMethod>();
             for (PsiMethod method : methods) {
@@ -240,6 +241,7 @@ public class PsiDocMethodOrFieldRef extends CompositePsiElement implements PsiDo
       return myReferencee == null ? JavaResolveResult.EMPTY_ARRAY : new JavaResolveResult[]{new CandidateInfo(myReferencee, PsiSubstitutor.EMPTY)};
     }
 
+    @NotNull
     public PsiElement[] getVariants(){
       final List<PsiModifierListOwner> vars = new ArrayList<PsiModifierListOwner>();
       final PsiElement scope = getScope();
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocParamRef.java b/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocParamRef.java
index 1c785c586311..992e92302a3a 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocParamRef.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/javadoc/PsiDocParamRef.java
@@ -100,6 +100,7 @@ public class PsiDocParamRef extends CompositePsiElement implements PsiDocTagValu
         return getManager().areElementsEquivalent(resolve(), element);
       }
 
+      @NotNull
       public Object[] getVariants() {
         final PsiElement firstChild = getFirstChild();
         if (firstChild instanceof PsiDocToken && ((PsiDocToken)firstChild).getTokenType().equals(JavaDocTokenType.DOC_TAG_VALUE_LT)) {
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/MethodPropertyReference.java b/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/MethodPropertyReference.java
index c0d884843bf2..a582a4d69936 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/MethodPropertyReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/MethodPropertyReference.java
@@ -23,6 +23,7 @@ import com.intellij.psi.xml.XmlAttribute;
 import com.intellij.psi.xml.XmlAttributeValue;
 import com.intellij.psi.xml.XmlTag;
 import com.intellij.util.IncorrectOperationException;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -93,6 +94,7 @@ public class MethodPropertyReference extends BasicAttributeValueReference {
     return super.handleElementRename(newElementName);
   }
 
+  @NotNull
   public Object[] getVariants() {
     return JspSpiUtil.getMethodPropertyReferenceVariants(this, resolveClass(), myReadable);
   }
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/PsiPackageReference.java b/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/PsiPackageReference.java
index 57e715307b89..3dc30b5f557e 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/PsiPackageReference.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/PsiPackageReference.java
@@ -46,6 +46,7 @@ public class PsiPackageReference extends PsiPolyVariantReferenceBase<PsiElement>
            (PsiPackage)myReferenceSet.getReference(myIndex - 1).resolve();
   }
 
+  @NotNull
   public Object[] getVariants() {
     final PsiPackage psiPackage = getContext();
     if (psiPackage == null) return ArrayUtil.EMPTY_OBJECT_ARRAY;
@@ -88,4 +89,4 @@ public class PsiPackageReference extends PsiPolyVariantReferenceBase<PsiElement>
   public PackageReferenceSet getReferenceSet() {
     return myReferenceSet;
   }
-}
\ No newline at end of file
+}
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNameValuePairImpl.java b/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNameValuePairImpl.java
index a24afb5db17b..9b0cf8fd6df9 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNameValuePairImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNameValuePairImpl.java
@@ -185,6 +185,7 @@ public class PsiNameValuePairImpl extends CompositePsiElement implements PsiName
         return element instanceof PsiMethod && element.equals(resolve());
       }
 
+      @NotNull
       public Object[] getVariants() {
         return ArrayUtil.EMPTY_OBJECT_ARRAY;
       }
diff --git a/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNewExpressionImpl.java b/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNewExpressionImpl.java
index 379787a85ad1..08b7ec622f15 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNewExpressionImpl.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/tree/java/PsiNewExpressionImpl.java
@@ -160,6 +160,7 @@ public class PsiNewExpressionImpl extends ExpressionPsiElement implements PsiNew
         return null;
       }
 
+      @NotNull
       public Object[] getVariants() {
         return ArrayUtil.EMPTY_OBJECT_ARRAY;
       }
diff --git a/java/java-tests/testSrc/com/intellij/codeInsight/completion/WordCompletionTest.java b/java/java-tests/testSrc/com/intellij/codeInsight/completion/WordCompletionTest.java
index 772d769a79ab..a91ff5ed2da1 100644
--- a/java/java-tests/testSrc/com/intellij/codeInsight/completion/WordCompletionTest.java
+++ b/java/java-tests/testSrc/com/intellij/codeInsight/completion/WordCompletionTest.java
@@ -48,6 +48,7 @@ public class WordCompletionTest extends CompletionTestCase {
             return true;
           }
 
+          @NotNull
           public Object[] getVariants() {
             return new Object[]{"MySoftVariant"};
           }
@@ -66,6 +67,7 @@ public class WordCompletionTest extends CompletionTestCase {
             return false;
           }
 
+          @NotNull
           public Object[] getVariants() {
             return new Object[]{"MyHardVariant"};
           }
diff --git a/platform/lang-api/src/com/intellij/openapi/roots/ProjectRootsTraversing.java b/platform/lang-api/src/com/intellij/openapi/roots/ProjectRootsTraversing.java
index d6391c012be2..8649f0ac31dc 100644
--- a/platform/lang-api/src/com/intellij/openapi/roots/ProjectRootsTraversing.java
+++ b/platform/lang-api/src/com/intellij/openapi/roots/ProjectRootsTraversing.java
@@ -24,6 +24,7 @@ import com.intellij.openapi.util.UserDataHolderBase;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.util.PathUtil;
 import com.intellij.util.PathsList;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.HashSet;
 import java.util.List;
@@ -125,11 +126,11 @@ public class ProjectRootsTraversing {
       myCurrentModuleManager = restored;
     }
 
-    public <T> T getUserData(Key<T> key) {
+    public <T> T getUserData(@NotNull Key<T> key) {
       return myUserData.getUserData(key);
     }
 
-    public <T> void putUserData(Key<T> key, T value) {
+    public <T> void putUserData(@NotNull Key<T> key, T value) {
       myUserData.putUserData(key, value);
     }
 
diff --git a/platform/lang-api/src/com/intellij/psi/PsiReferenceBase.java b/platform/lang-api/src/com/intellij/psi/PsiReferenceBase.java
index 3e150e937ab2..99aeb7473dd5 100644
--- a/platform/lang-api/src/com/intellij/psi/PsiReferenceBase.java
+++ b/platform/lang-api/src/com/intellij/psi/PsiReferenceBase.java
@@ -118,6 +118,7 @@ public abstract class PsiReferenceBase<T extends PsiElement> implements PsiRefer
         return resolveTo;
       }
 
+      @NotNull
       public Object[] getVariants() {
         return EMPTY_ARRAY;
       }
diff --git a/platform/lang-api/src/com/intellij/psi/TokenType.java b/platform/lang-api/src/com/intellij/psi/TokenType.java
index 795d8cd74301..86f287796823 100644
--- a/platform/lang-api/src/com/intellij/psi/TokenType.java
+++ b/platform/lang-api/src/com/intellij/psi/TokenType.java
@@ -16,7 +16,6 @@
 package com.intellij.psi;
 
 import com.intellij.lang.Language;
-import com.intellij.openapi.fileTypes.FileTypes;
 import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.tree.IFileElementType;
 
diff --git a/platform/lang-api/src/com/intellij/psi/util/PsiUtilBase.java b/platform/lang-api/src/com/intellij/psi/util/PsiUtilBase.java
index b4026f9fc6b5..34509ab6cb43 100644
--- a/platform/lang-api/src/com/intellij/psi/util/PsiUtilBase.java
+++ b/platform/lang-api/src/com/intellij/psi/util/PsiUtilBase.java
@@ -254,11 +254,11 @@ public class PsiUtilBase {
         return null;
       }
 
-      public <T> T getUserData(Key<T> key) {
+      public <T> T getUserData(@NotNull Key<T> key) {
         return null;
       }
 
-      public <T> void putUserData(Key<T> key, T value) {
+      public <T> void putUserData(@NotNull Key<T> key, T value) {
 
       }
 
diff --git a/platform/lang-impl/src/com/intellij/codeInspection/reference/RefEntityImpl.java b/platform/lang-impl/src/com/intellij/codeInspection/reference/RefEntityImpl.java
index 1f5492eb9c23..33e2bf36b7ea 100644
--- a/platform/lang-impl/src/com/intellij/codeInspection/reference/RefEntityImpl.java
+++ b/platform/lang-impl/src/com/intellij/codeInspection/reference/RefEntityImpl.java
@@ -28,6 +28,7 @@ import com.intellij.codeInspection.InspectionsBundle;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.util.Key;
 import gnu.trove.THashMap;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
@@ -90,7 +91,7 @@ public abstract class RefEntityImpl implements RefEntity {
   }
   
  @Nullable
-  public <T> T getUserData(Key<T> key){
+  public <T> T getUserData(@NotNull Key<T> key){
     synchronized(this){
       if (myUserMap == null) return null;
       //noinspection unchecked
@@ -106,7 +107,7 @@ public abstract class RefEntityImpl implements RefEntity {
     });
   }
 
-  public <T> void putUserData(Key<T> key, T value){
+  public <T> void putUserData(@NotNull Key<T> key, T value){
     synchronized(this){
       if (myUserMap == null){
         if (value == null) return;
diff --git a/platform/lang-impl/src/com/intellij/injected/editor/RangeMarkerWindow.java b/platform/lang-impl/src/com/intellij/injected/editor/RangeMarkerWindow.java
index a7cecb3acf8b..134eb1c6b5b1 100644
--- a/platform/lang-impl/src/com/intellij/injected/editor/RangeMarkerWindow.java
+++ b/platform/lang-impl/src/com/intellij/injected/editor/RangeMarkerWindow.java
@@ -65,11 +65,11 @@ public class RangeMarkerWindow implements RangeMarkerEx {
     myHostMarker.setGreedyToRight(greedy);
   }
 
-  public <T> T getUserData(final Key<T> key) {
+  public <T> T getUserData(@NotNull final Key<T> key) {
     return myHostMarker.getUserData(key);
   }
 
-  public <T> void putUserData(final Key<T> key, final T value) {
+  public <T> void putUserData(@NotNull final Key<T> key, final T value) {
     myHostMarker.putUserData(key, value);
   }
 
@@ -91,4 +91,4 @@ public class RangeMarkerWindow implements RangeMarkerEx {
   public boolean isGreedyToLeft() {
     return myHostMarker.isGreedyToLeft();
   }
-}
\ No newline at end of file
+}
diff --git a/platform/lang-impl/src/com/intellij/mock/MockPsiManager.java b/platform/lang-impl/src/com/intellij/mock/MockPsiManager.java
index 65ea995863cb..5458638bce6b 100644
--- a/platform/lang-impl/src/com/intellij/mock/MockPsiManager.java
+++ b/platform/lang-impl/src/com/intellij/mock/MockPsiManager.java
@@ -145,11 +145,11 @@ public class MockPsiManager extends PsiManagerEx {
   public void finishBatchFilesProcessingMode() {
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     return null;
   }
 
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
   }
 
   public boolean isDisposed() {
@@ -250,4 +250,4 @@ public class MockPsiManager extends PsiManagerEx {
   public CacheManager getCacheManager() {
     return myCompositeCacheManager;
   }
-}
\ No newline at end of file
+}
diff --git a/platform/lang-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/PsiMultiReference.java b/platform/lang-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/PsiMultiReference.java
index 31b845def30a..c1670b02592f 100644
--- a/platform/lang-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/PsiMultiReference.java
+++ b/platform/lang-impl/src/com/intellij/psi/impl/source/resolve/reference/impl/PsiMultiReference.java
@@ -127,6 +127,7 @@ public class PsiMultiReference implements PsiPolyVariantReference {
     return false;
   }
 
+  @NotNull
   public Object[] getVariants() {
     Set<Object> variants = new HashSet<Object>();
     for(PsiReference ref: myReferences) {
diff --git a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EmptyMarkupModel.java b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EmptyMarkupModel.java
index 907486af825e..eb86a65e1c29 100644
--- a/platform/platform-impl/src/com/intellij/openapi/editor/impl/EmptyMarkupModel.java
+++ b/platform/platform-impl/src/com/intellij/openapi/editor/impl/EmptyMarkupModel.java
@@ -54,11 +54,11 @@ public class EmptyMarkupModel implements MarkupModelEx {
     return RangeHighlighter.EMPTY_ARRAY;
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     return null;
   }
 
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
   }
 
   public void dispose() {
diff --git a/platform/testFramework/src/com/intellij/mock/MockDocument.java b/platform/testFramework/src/com/intellij/mock/MockDocument.java
index 6eee48594df8..07ff7eb4db50 100644
--- a/platform/testFramework/src/com/intellij/mock/MockDocument.java
+++ b/platform/testFramework/src/com/intellij/mock/MockDocument.java
@@ -156,12 +156,12 @@ public class MockDocument implements DocumentEx {
   }
 
   @SuppressWarnings({"unchecked"})
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     return (T)myUserData.get(key);
   }
 
   @SuppressWarnings({"unchecked"})
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
     myUserData.put(key, value);
   }
 
diff --git a/platform/util/src/com/intellij/openapi/util/UserDataHolderBase.java b/platform/util/src/com/intellij/openapi/util/UserDataHolderBase.java
index b2acd934eed1..056dee0267ff 100644
--- a/platform/util/src/com/intellij/openapi/util/UserDataHolderBase.java
+++ b/platform/util/src/com/intellij/openapi/util/UserDataHolderBase.java
@@ -70,12 +70,12 @@ public class UserDataHolderBase implements UserDataHolderEx, Cloneable {
     }
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     final Map<Key, Object> map = myUserMap;
     return map == null ? null : (T)map.get(key);
   }
 
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
     Map<Key, Object> map = getOrCreateMap();
 
     if (value == null) {
diff --git a/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/LanguageReference.java b/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/LanguageReference.java
index 91c903b30694..65b760e0d65a 100644
--- a/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/LanguageReference.java
+++ b/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/LanguageReference.java
@@ -26,6 +26,7 @@ import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.ui.EmptyIcon;
 import org.intellij.plugins.intelliLang.inject.InjectedLanguage;
 import org.intellij.plugins.intelliLang.util.StringLiteralReference;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -47,6 +48,7 @@ final class LanguageReference extends StringLiteralReference {
     return false;
   }
 
+  @NotNull
   public Object[] getVariants() {
     final String[] ids = InjectedLanguage.getAvailableLanguageIDs();
     return ContainerUtil.map2Array(ids, LookupElement.class, new Function<String, LookupElement>() {
diff --git a/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/RegExpEnumReference.java b/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/RegExpEnumReference.java
index 38c5550c8f51..f2c43283e887 100644
--- a/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/RegExpEnumReference.java
+++ b/plugins/IntelliLang/src/org/intellij/plugins/intelliLang/inject/java/RegExpEnumReference.java
@@ -42,6 +42,7 @@ final class RegExpEnumReference extends StringLiteralReference {
     myPattern = pattern;
   }
 
+  @NotNull
   public Object[] getVariants() {
     final Set<String> values = getEnumValues();
     if (values == null || values.size() == 0) {
@@ -68,4 +69,4 @@ final class RegExpEnumReference extends StringLiteralReference {
   private Set<String> getEnumValues() {
     return RegExpUtil.getEnumValues(myValue.getProject(), myPattern);
   }
-}
\ No newline at end of file
+}
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntAttributeReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntAttributeReference.java
index 578ef2bea5ef..22020a7de486 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntAttributeReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntAttributeReference.java
@@ -51,6 +51,7 @@ public class AntAttributeReference extends AntGenericReference {
     return null;
   }
 
+  @NotNull
   public Object[] getVariants() {
     final AntTypeDefinition def = getElement().getTypeDefinition();
     return (def == null) ? EMPTY_ARRAY : def.getAttributes();
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntElementNameReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntElementNameReference.java
index c20fad203729..b2386f52706d 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntElementNameReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntElementNameReference.java
@@ -117,6 +117,7 @@ public class AntElementNameReference extends AntGenericReference {
     return true;
   }
 
+  @NotNull
   public Object[] getVariants() {
     if (getAttribute() != null) {
       return EMPTY_ARRAY; // scriptdef or mactodef params will be handled by XML implementation
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntEntityReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntEntityReference.java
index 3587b5e64e51..2817c3ba8835 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntEntityReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntEntityReference.java
@@ -62,6 +62,7 @@ public class AntEntityReference implements PsiReference {
     return myXmlRef.isReferenceTo(element);
   }
 
+  @NotNull
   public Object[] getVariants() {
     return EMPTY_ARRAY;
   }
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntMacroDefParameterReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntMacroDefParameterReference.java
index e9875c15a2ea..d20fb6294d12 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntMacroDefParameterReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntMacroDefParameterReference.java
@@ -97,6 +97,7 @@ public class AntMacroDefParameterReference extends AntGenericReference {
     return null;
   }
 
+  @NotNull
   @SuppressWarnings({"HardCodedStringLiteral"})
   public Object[] getVariants() {
     final Set<String> variants = StringSetSpinAllocator.alloc();
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntPropertyReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntPropertyReference.java
index b3427d0320ab..8368aa6954d3 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntPropertyReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntPropertyReference.java
@@ -119,6 +119,7 @@ public class AntPropertyReference extends AntGenericReference {
     return AntBundle.message("unknown.property", getCanonicalText());
   }
 
+  @NotNull
   public Object[] getVariants() {
     final AntElement currentElement = getElement();
     final Set<PsiElement> variants = PsiElementSetSpinAllocator.alloc();
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntRefIdReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntRefIdReference.java
index 64981f1b7404..ba26c6183476 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntRefIdReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntRefIdReference.java
@@ -77,6 +77,7 @@ public class AntRefIdReference extends AntGenericReference {
     }
   }
 
+  @NotNull
   public Object[] getVariants() {
     final Set<PsiElement> variants = PsiElementSetSpinAllocator.alloc();
     try {
diff --git a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntTargetReference.java b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntTargetReference.java
index ffe35c35979f..4eb610c7a65f 100644
--- a/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntTargetReference.java
+++ b/plugins/ant/src/com/intellij/lang/ant/psi/impl/reference/AntTargetReference.java
@@ -153,6 +153,7 @@ public class AntTargetReference extends AntGenericReference {
     }
   }
 
+  @NotNull
   public Object[] getVariants() {
     final AntElement element = getElement();
     if (element instanceof AntAntImpl) {
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/groovydoc/psi/impl/GrDocParameterReferenceImpl.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/groovydoc/psi/impl/GrDocParameterReferenceImpl.java
index 3c404ff89079..7d9fecffa82a 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/groovydoc/psi/impl/GrDocParameterReferenceImpl.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/groovydoc/psi/impl/GrDocParameterReferenceImpl.java
@@ -131,6 +131,7 @@ public class GrDocParameterReferenceImpl extends GroovyDocPsiElementImpl impleme
     return getManager().areElementsEquivalent(element, resolve());
   }
 
+  @NotNull
   public Object[] getVariants() {
     final PsiElement owner = GrDocCommentUtil.findDocOwner(this);
     final PsiElement firstChild = getFirstChild();
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/auxiliary/annotation/GrAnnotationNameValuePairImpl.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/auxiliary/annotation/GrAnnotationNameValuePairImpl.java
index 291a41b6201c..39b33c697d3c 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/auxiliary/annotation/GrAnnotationNameValuePairImpl.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/auxiliary/annotation/GrAnnotationNameValuePairImpl.java
@@ -145,6 +145,7 @@ public class GrAnnotationNameValuePairImpl extends GroovyPsiElementImpl implemen
     return element instanceof PsiMethod && getManager().areElementsEquivalent(element, resolve());
   }
 
+  @NotNull
   public Object[] getVariants() {
     GrAnnotation anno = getAnnotation();
     if (anno != null) {
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/GrConstructorInvocationImpl.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/GrConstructorInvocationImpl.java
index 63a2d15ef922..363e43c92a6f 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/GrConstructorInvocationImpl.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/GrConstructorInvocationImpl.java
@@ -160,6 +160,7 @@ public class GrConstructorInvocationImpl extends GroovyPsiElementImpl implements
 
   }
 
+  @NotNull
   public Object[] getVariants() {
     return ArrayUtil.EMPTY_OBJECT_ARRAY;
   }
diff --git a/plugins/maven/src/main/java/org/jetbrains/idea/maven/dom/references/MavenModulePsiReference.java b/plugins/maven/src/main/java/org/jetbrains/idea/maven/dom/references/MavenModulePsiReference.java
index a475a6ca0885..48fde73e1ec1 100644
--- a/plugins/maven/src/main/java/org/jetbrains/idea/maven/dom/references/MavenModulePsiReference.java
+++ b/plugins/maven/src/main/java/org/jetbrains/idea/maven/dom/references/MavenModulePsiReference.java
@@ -56,6 +56,7 @@ public class MavenModulePsiReference extends MavenPsiReference implements LocalQ
     return getPsiFile(file);
   }
 
+  @NotNull
   public Object[] getVariants() {
     List<DomFileElement<MavenDomProjectModel>> files = MavenDomUtil.collectProjectModels(getProject());
 
diff --git a/plugins/testng/src/com/theoryinpractice/testng/TestNGReferenceContributor.java b/plugins/testng/src/com/theoryinpractice/testng/TestNGReferenceContributor.java
index 4a63ce22c848..930feff3bbbe 100644
--- a/plugins/testng/src/com/theoryinpractice/testng/TestNGReferenceContributor.java
+++ b/plugins/testng/src/com/theoryinpractice/testng/TestNGReferenceContributor.java
@@ -109,6 +109,7 @@ public class TestNGReferenceContributor extends PsiReferenceContributor {
       return null;
     }
 
+    @NotNull
     public Object[] getVariants() {
       final List<Object> list = new ArrayList<Object>();
       final PsiClass cls = PsiUtil.getTopLevelClass(getElement());
@@ -159,6 +160,7 @@ public class TestNGReferenceContributor extends PsiReferenceContributor {
       return null;
     }
 
+    @NotNull
     public Object[] getVariants() {
       List<Object> list = new ArrayList<Object>();
       PsiClass cls = PsiUtil.getTopLevelClass(getElement());
@@ -189,6 +191,7 @@ public class TestNGReferenceContributor extends PsiReferenceContributor {
       return null;
     }
 
+    @NotNull
     public Object[] getVariants() {
       List<Object> list = new ArrayList<Object>();
 
diff --git a/plugins/ui-designer/src/com/intellij/uiDesigner/binding/ReferenceInForm.java b/plugins/ui-designer/src/com/intellij/uiDesigner/binding/ReferenceInForm.java
index 0a62834a3ded..3e94d99bad1c 100644
--- a/plugins/ui-designer/src/com/intellij/uiDesigner/binding/ReferenceInForm.java
+++ b/plugins/ui-designer/src/com/intellij/uiDesigner/binding/ReferenceInForm.java
@@ -25,6 +25,7 @@ import com.intellij.psi.PsiPlainTextFile;
 import com.intellij.psi.PsiReference;
 import com.intellij.util.ArrayUtil;
 import org.jetbrains.annotations.NonNls;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author Eugene Zhuravlev
@@ -75,6 +76,7 @@ public abstract class ReferenceInForm implements PsiReference {
     return resolve() == element;
   }
 
+  @NotNull
   public Object[] getVariants() {
     return ArrayUtil.EMPTY_OBJECT_ARRAY;
   }
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/PrefixReferenceImpl.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/PrefixReferenceImpl.java
index 6d4405a33751..a4f86fddd633 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/PrefixReferenceImpl.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/PrefixReferenceImpl.java
@@ -22,6 +22,7 @@ import org.intellij.lang.xpath.psi.QNameElement;
 
 import com.intellij.lang.ASTNode;
 import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 class PrefixReferenceImpl extends ReferenceBase implements PrefixReference {
@@ -45,6 +46,7 @@ class PrefixReferenceImpl extends ReferenceBase implements PrefixReference {
         return element.equals(resolve());
     }
 
+    @NotNull
     public Object[] getVariants() {
         // handled in XPathCompletionData
         return EMPTY_ARRAY;
@@ -69,4 +71,4 @@ class PrefixReferenceImpl extends ReferenceBase implements PrefixReference {
         final String prefix = getCanonicalText();
         return !namespaceContext.getKnownPrefixes(myProvider.getContextElement()).contains(prefix);
     }
-}
\ No newline at end of file
+}
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/ReferenceBase.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/ReferenceBase.java
index c2887c2f3ddf..877e17e1010d 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/ReferenceBase.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/ReferenceBase.java
@@ -65,6 +65,7 @@ public abstract class ReferenceBase implements PsiReference {
         return Comparing.equal(resolve(), element);
     }
 
+    @NotNull
     public abstract Object[] getVariants();
 
     public boolean isSoft() {
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathFunctionCallImpl.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathFunctionCallImpl.java
index 43e3035dfa52..5be6c8dc1c40 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathFunctionCallImpl.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathFunctionCallImpl.java
@@ -156,6 +156,7 @@ public class XPathFunctionCallImpl extends XPathElementImpl implements XPathFunc
             }
         }
 
+        @NotNull
         public Object[] getVariants() {
             return EMPTY_ARRAY;
         }
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathNodeTestImpl.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathNodeTestImpl.java
index 952a4510ff74..17916be11749 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathNodeTestImpl.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathNodeTestImpl.java
@@ -110,6 +110,7 @@ public class XPathNodeTestImpl extends XPathElementImpl implements XPathNodeTest
             super(element, nameNode);
         }
 
+        @NotNull
         public Object[] getVariants() {
             // handled in XPathCompletionData
             return EMPTY_ARRAY;
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathVariableReferenceImpl.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathVariableReferenceImpl.java
index 261c7479b3bd..580f738e5047 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathVariableReferenceImpl.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/psi/impl/XPathVariableReferenceImpl.java
@@ -133,6 +133,7 @@ public class XPathVariableReferenceImpl extends XPathElementImpl implements XPat
         return false;
     }
 
+    @NotNull
     public Object[] getVariants() {
         return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/AttributeReference.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/AttributeReference.java
index df35fc89239a..2f60e3559541 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/AttributeReference.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/AttributeReference.java
@@ -33,6 +33,7 @@ class AttributeReference extends SimpleAttributeReference {
         mySoft = soft;
     }
 
+    @NotNull
     public Object[] getVariants() {
         return ResolveUtil.collect(myMatcher.variantMatcher());
     }
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ExternalResourceReference.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ExternalResourceReference.java
index c633ad6fd1e9..3548f3f84302 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ExternalResourceReference.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ExternalResourceReference.java
@@ -102,6 +102,7 @@ class ExternalResourceReference implements PsiReference, QuickFixProvider<Extern
         return element == resolve();
     }
 
+    @NotNull
     public Object[] getVariants() {
         return myResourceManager.getResourceUrls(null, false);
     }
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ModeReference.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ModeReference.java
index b28d84643769..7cb48dc53c23 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ModeReference.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/ModeReference.java
@@ -64,6 +64,7 @@ class ModeReference extends SimpleAttributeReference implements PsiPolyVariantRe
         return myImplicitModeElement.getModeRange();
     }
 
+    @NotNull
     public Object[] getVariants() {
         final PsiFile containingFile = myAttribute.getContainingFile();
         if (containingFile instanceof XmlFile && XsltSupport.isXsltFile(containingFile)) {
@@ -146,6 +147,7 @@ class ModeReference extends SimpleAttributeReference implements PsiPolyVariantRe
             super(attribute);
         }
 
+        @NotNull
         public Object[] getVariants() {
             return getPrefixCompletions(myAttribute);
         }
@@ -231,4 +233,4 @@ class ModeReference extends SimpleAttributeReference implements PsiPolyVariantRe
             return "Undefined mode ''{0}''";
         }
     }
-}
\ No newline at end of file
+}
diff --git a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/SelfReference.java b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/SelfReference.java
index 824acf711165..5eaf0e6d5e11 100644
--- a/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/SelfReference.java
+++ b/plugins/xpath/xpath-lang/src/org/intellij/lang/xpath/xslt/impl/references/SelfReference.java
@@ -64,6 +64,7 @@ class SelfReference implements PsiReference {
         return false;
     }
 
+    @NotNull
     public Object[] getVariants() {
         return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
diff --git a/xml/dom-impl/src/com/intellij/util/xml/impl/DomFileElementImpl.java b/xml/dom-impl/src/com/intellij/util/xml/impl/DomFileElementImpl.java
index a4d19f215895..ed1d87dc4f25 100644
--- a/xml/dom-impl/src/com/intellij/util/xml/impl/DomFileElementImpl.java
+++ b/xml/dom-impl/src/com/intellij/util/xml/impl/DomFileElementImpl.java
@@ -353,11 +353,11 @@ public class DomFileElementImpl<T extends DomElement> implements DomFileElement<
     getRootElement().accept(visitor);
   }
 
-  public <T> T getUserData(Key<T> key) {
+  public <T> T getUserData(@NotNull Key<T> key) {
     return (T)myUserData.get(key);
   }
 
-  public <T> void putUserData(Key<T> key, T value) {
+  public <T> void putUserData(@NotNull Key<T> key, T value) {
     myUserData.put(key, value);
   }
 
diff --git a/xml/dom-impl/src/com/intellij/util/xml/impl/GenericDomValueReference.java b/xml/dom-impl/src/com/intellij/util/xml/impl/GenericDomValueReference.java
index 4877c1bbdef5..d01679d80738 100644
--- a/xml/dom-impl/src/com/intellij/util/xml/impl/GenericDomValueReference.java
+++ b/xml/dom-impl/src/com/intellij/util/xml/impl/GenericDomValueReference.java
@@ -177,6 +177,7 @@ public class GenericDomValueReference<T> extends PsiReferenceBase<XmlElement> im
     return null;
   }
 
+  @NotNull
   public Object[] getVariants() {
     final Converter<T> converter = getConverter();
     if (converter instanceof EnumConverter || converter == ResolvingConverter.BOOLEAN_CONVERTER) {
diff --git a/xml/dom-impl/src/com/intellij/util/xml/impl/GenericValueReferenceProvider.java b/xml/dom-impl/src/com/intellij/util/xml/impl/GenericValueReferenceProvider.java
index 4a9a36133de6..9fea4de86318 100644
--- a/xml/dom-impl/src/com/intellij/util/xml/impl/GenericValueReferenceProvider.java
+++ b/xml/dom-impl/src/com/intellij/util/xml/impl/GenericValueReferenceProvider.java
@@ -172,6 +172,7 @@ public class GenericValueReferenceProvider extends PsiReferenceProvider {
 
     if (ReflectionCache.isAssignable(Integer.class, clazz)) {
       return new PsiReference[]{new GenericDomValueReference<Integer>((GenericDomValue<Integer>)domValue) {
+        @NotNull
         public Object[] getVariants() {
           return new Object[]{"0"};
         }
diff --git a/xml/dom-openapi/src/com/intellij/util/xml/converters/DelimitedListConverter.java b/xml/dom-openapi/src/com/intellij/util/xml/converters/DelimitedListConverter.java
index 8f490a2d9054..e8b12e646afb 100644
--- a/xml/dom-openapi/src/com/intellij/util/xml/converters/DelimitedListConverter.java
+++ b/xml/dom-openapi/src/com/intellij/util/xml/converters/DelimitedListConverter.java
@@ -185,6 +185,7 @@ public abstract class DelimitedListConverter<T> extends ResolvingConverter<List<
       return resolveReference(convertString(value, myContext), myContext);
     }
 
+    @NotNull
     public Object[] getVariants() {
       return getReferenceVariants(myContext, myGenericDomValue);
     }
@@ -260,4 +261,4 @@ public abstract class DelimitedListConverter<T> extends ResolvingConverter<List<
     return superHandleElementRename.fun(newName);
   }
 
-}
\ No newline at end of file
+}
diff --git a/xml/dom-openapi/src/com/intellij/util/xml/converters/QuotedValueConverter.java b/xml/dom-openapi/src/com/intellij/util/xml/converters/QuotedValueConverter.java
index dac501ff75b3..ec028e6b0456 100644
--- a/xml/dom-openapi/src/com/intellij/util/xml/converters/QuotedValueConverter.java
+++ b/xml/dom-openapi/src/com/intellij/util/xml/converters/QuotedValueConverter.java
@@ -143,6 +143,7 @@ public abstract class QuotedValueConverter<T> extends ResolvingConverter<T> impl
       return multiResolveReference(convertString(value, myContext), myContext);
     }
 
+    @NotNull
     public Object[] getVariants() {
       return getReferenceVariants(myContext, myGenericDomValue, getRangeInElement());
     }
diff --git a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/AttributeValueSelfReference.java b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/AttributeValueSelfReference.java
index 7a687801d24f..9ecba6f551a2 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/AttributeValueSelfReference.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/AttributeValueSelfReference.java
@@ -18,6 +18,7 @@ package com.intellij.psi.impl.source.resolve.reference.impl.providers;
 import com.intellij.openapi.util.TextRange;
 import com.intellij.psi.PsiElement;
 import com.intellij.util.ArrayUtil;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -41,6 +42,7 @@ public class AttributeValueSelfReference extends BasicAttributeValueReference {
     return myElement;
   }
 
+  @NotNull
   public Object[] getVariants() {
     return ArrayUtil.EMPTY_OBJECT_ARRAY;
   }
diff --git a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/DtdReferencesProvider.java b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/DtdReferencesProvider.java
index b3a385933adb..66a3b512b747 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/DtdReferencesProvider.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/DtdReferencesProvider.java
@@ -136,6 +136,7 @@ public class DtdReferencesProvider extends PsiReferenceProvider {
       return myElement.getManager().areElementsEquivalent(element, resolve());
     }
 
+    @NotNull
     public Object[] getVariants() {
       final XmlNSDescriptor rootTagNSDescriptor = getNsDescriptor();
       return rootTagNSDescriptor != null ?
@@ -226,6 +227,7 @@ public class DtdReferencesProvider extends PsiReferenceProvider {
       return myElement.getManager().areElementsEquivalent(resolve(), element);
     }
 
+    @NotNull
     public Object[] getVariants() {
       return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
diff --git a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/IdRefReference.java b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/IdRefReference.java
index 1c884cde28e0..c8ec76e80668 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/IdRefReference.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/IdRefReference.java
@@ -157,6 +157,7 @@ public class IdRefReference extends BasicAttributeValueReference {
     return result[0];
   }
 
+  @NotNull
   public Object[] getVariants() {
     final List<String> result = new LinkedList<String>();
 
diff --git a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/SchemaReferencesProvider.java b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/SchemaReferencesProvider.java
index 35d215cd7583..068b66c16d6a 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/SchemaReferencesProvider.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/SchemaReferencesProvider.java
@@ -116,6 +116,7 @@ public class SchemaReferencesProvider extends PsiReferenceProvider {
       }
     }
 
+    @NotNull
     public Object[] getVariants() {
       return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
@@ -170,6 +171,7 @@ public class SchemaReferencesProvider extends PsiReferenceProvider {
       return myElement.getManager().areElementsEquivalent(resolve(), element);
     }
 
+    @NotNull
     public Object[] getVariants() {
       return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
@@ -454,6 +456,7 @@ public class SchemaReferencesProvider extends PsiReferenceProvider {
       }
     }
 
+    @NotNull
     public Object[] getVariants() {
       final XmlTag tag = PsiTreeUtil.getParentOfType(myElement, XmlTag.class);
       if (tag == null) return null;
diff --git a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/URIReferenceProvider.java b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/URIReferenceProvider.java
index 6dbcab0dbda9..860cad0634d9 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/URIReferenceProvider.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/resolve/reference/impl/providers/URIReferenceProvider.java
@@ -88,6 +88,7 @@ public class URIReferenceProvider extends PsiReferenceProvider {
       return myReference.resolve();
     }
 
+    @NotNull
     public Object[] getVariants() {
       return ArrayUtil.EMPTY_OBJECT_ARRAY;
     }
diff --git a/xml/impl/src/com/intellij/psi/impl/source/xml/TagNameReference.java b/xml/impl/src/com/intellij/psi/impl/source/xml/TagNameReference.java
index b1a0683c35ab..80270442197b 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/xml/TagNameReference.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/xml/TagNameReference.java
@@ -169,6 +169,7 @@ public class TagNameReference implements PsiReference {
     return getElement().getManager().areElementsEquivalent(element, resolve());
   }
 
+  @NotNull
   public Object[] getVariants(){
     final PsiElement element = getElement();
     if(!myStartTagFlag){
diff --git a/xml/impl/src/com/intellij/psi/impl/source/xml/XmlAttributeImpl.java b/xml/impl/src/com/intellij/psi/impl/source/xml/XmlAttributeImpl.java
index f0c74823fe05..a4a329875749 100644
--- a/xml/impl/src/com/intellij/psi/impl/source/xml/XmlAttributeImpl.java
+++ b/xml/impl/src/com/intellij/psi/impl/source/xml/XmlAttributeImpl.java
@@ -420,6 +420,7 @@ public class XmlAttributeImpl extends XmlElementImpl implements XmlAttribute {
       return getManager().areElementsEquivalent(element, resolve());
     }
 
+    @NotNull
     public Object[] getVariants() {
       final List<MutableLookupElement<String>> variants = new ArrayList<MutableLookupElement<String>>();
 
diff --git a/xml/impl/src/com/intellij/xml/util/AnchorReference.java b/xml/impl/src/com/intellij/xml/util/AnchorReference.java
index 1b8bff853027..e829e1df2ff5 100644
--- a/xml/impl/src/com/intellij/xml/util/AnchorReference.java
+++ b/xml/impl/src/com/intellij/xml/util/AnchorReference.java
@@ -196,6 +196,7 @@ class AnchorReference implements PsiReference, EmptyResolveMessageProvider {
     return myElement.getManager().areElementsEquivalent(element,resolve());
   }
 
+  @NotNull
   public Object[] getVariants() {
     final Map<String, XmlTag> idMap = getIdMap();
     if (idMap == null) return ArrayUtil.EMPTY_OBJECT_ARRAY;