diff --git a/compiler/frontend/src/org/jetbrains/jet/checkers/DebugInfoUtil.java b/compiler/frontend/src/org/jetbrains/jet/checkers/DebugInfoUtil.java
index 30d7793613c..5cdf0554c47 100644
--- a/compiler/frontend/src/org/jetbrains/jet/checkers/DebugInfoUtil.java
+++ b/compiler/frontend/src/org/jetbrains/jet/checkers/DebugInfoUtil.java
@@ -26,8 +26,10 @@ import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
 import org.jetbrains.jet.lang.diagnostics.AbstractDiagnosticFactory;
 import org.jetbrains.jet.lang.diagnostics.Diagnostic;
 import org.jetbrains.jet.lang.diagnostics.Errors;
-import org.jetbrains.jet.lang.diagnostics.UnresolvedReferenceDiagnosticFactory;
-import org.jetbrains.jet.lang.psi.*;
+import org.jetbrains.jet.lang.psi.JetReferenceExpression;
+import org.jetbrains.jet.lang.psi.JetSimpleNameExpression;
+import org.jetbrains.jet.lang.psi.JetSuperExpression;
+import org.jetbrains.jet.lang.psi.JetTreeVisitorVoid;
 import org.jetbrains.jet.lang.resolve.BindingContext;
 import org.jetbrains.jet.lang.types.ErrorUtils;
 import org.jetbrains.jet.lang.types.JetType;
@@ -38,8 +40,6 @@ import java.util.Map;
 
 import static org.jetbrains.jet.lang.resolve.BindingContext.*;
 import static org.jetbrains.jet.lexer.JetTokens.*;
-import static org.jetbrains.jet.lexer.JetTokens.ELVIS;
-import static org.jetbrains.jet.lexer.JetTokens.EXCLEXCL;
 
 public class DebugInfoUtil {
     private static final TokenSet EXCLUDED = TokenSet.create(
@@ -62,7 +62,7 @@ public class DebugInfoUtil {
         final Map<JetReferenceExpression, AbstractDiagnosticFactory> markedWithErrorElements = Maps.newHashMap();
         for (Diagnostic diagnostic : bindingContext.getDiagnostics()) {
             AbstractDiagnosticFactory factory = diagnostic.getFactory();
-            if (factory instanceof UnresolvedReferenceDiagnosticFactory) {
+            if (Errors.UNRESOLVED_REFERENCE_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                 markedWithErrorElements.put((JetReferenceExpression) diagnostic.getPsiElement(), factory);
             }
             else if (factory == Errors.SUPER_IS_NOT_AN_EXPRESSION
@@ -130,7 +130,7 @@ public class DebugInfoUtil {
                     }
                 }
                 if (resolved && markedWithError) {
-                    if (factory instanceof UnresolvedReferenceDiagnosticFactory) {
+                    if (Errors.UNRESOLVED_REFERENCE_DIAGNOSTICS.contains(factory)) {
                         debugInfoReporter.reportUnresolvedWithTarget(expression, target);
                     }
                 }
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java b/compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java
index ac20144934c..657eccab687 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java
@@ -16,6 +16,7 @@
 
 package org.jetbrains.jet.lang.diagnostics;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiNameIdentifierOwner;
@@ -531,6 +532,14 @@ public interface Errors {
     DiagnosticFactory1<PsiElement, ClassDescriptor> INACCESSIBLE_OUTER_CLASS_EXPRESSION = DiagnosticFactory1.create(ERROR);
     SimpleDiagnosticFactory<PsiElement> NESTED_CLASS_NOT_ALLOWED = SimpleDiagnosticFactory.create(ERROR);
 
+
+    // Error sets
+    ImmutableSet<? extends AbstractDiagnosticFactory> UNRESOLVED_REFERENCE_DIAGNOSTICS = ImmutableSet.of(
+            UNRESOLVED_REFERENCE, NAMED_PARAMETER_NOT_FOUND);
+    ImmutableSet<? extends AbstractDiagnosticFactory> UNUSED_ELEMENT_DIAGNOSTICS = ImmutableSet.of(
+            UNUSED_VARIABLE, UNUSED_PARAMETER, ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE);
+    ImmutableSet<? extends AbstractDiagnosticFactory> REDECLARATION_DIAGNOSTICS = ImmutableSet.of(
+            REDECLARATION, NAME_SHADOWING);
     ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
     // This field is needed to make the Initializer class load (interfaces cannot have static initializers)
diff --git a/compiler/tests/org/jetbrains/jet/JetTestUtils.java b/compiler/tests/org/jetbrains/jet/JetTestUtils.java
index 59638523f89..9aa967a02e9 100644
--- a/compiler/tests/org/jetbrains/jet/JetTestUtils.java
+++ b/compiler/tests/org/jetbrains/jet/JetTestUtils.java
@@ -40,8 +40,8 @@ import org.jetbrains.jet.codegen.forTestCompile.ForTestPackJdkAnnotations;
 import org.jetbrains.jet.config.CommonConfigurationKeys;
 import org.jetbrains.jet.config.CompilerConfiguration;
 import org.jetbrains.jet.lang.diagnostics.Diagnostic;
+import org.jetbrains.jet.lang.diagnostics.Errors;
 import org.jetbrains.jet.lang.diagnostics.Severity;
-import org.jetbrains.jet.lang.diagnostics.UnresolvedReferenceDiagnosticFactory;
 import org.jetbrains.jet.lang.diagnostics.rendering.DefaultErrorMessages;
 import org.jetbrains.jet.lang.psi.JetFile;
 import org.jetbrains.jet.lang.psi.JetPsiFactory;
@@ -134,7 +134,7 @@ public class JetTestUtils {
 
         @Override
         public void report(@NotNull Diagnostic diagnostic) {
-            if (diagnostic.getFactory() instanceof UnresolvedReferenceDiagnosticFactory) {
+            if (Errors.UNRESOLVED_REFERENCE_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                 throw new IllegalStateException("Unresolved: " + diagnostic.getPsiElement().getText());
             }
         }
diff --git a/compiler/tests/org/jetbrains/jet/resolve/ExpectedResolveData.java b/compiler/tests/org/jetbrains/jet/resolve/ExpectedResolveData.java
index f3642dce155..2201f9ff865 100644
--- a/compiler/tests/org/jetbrains/jet/resolve/ExpectedResolveData.java
+++ b/compiler/tests/org/jetbrains/jet/resolve/ExpectedResolveData.java
@@ -33,7 +33,7 @@ import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
 import org.jetbrains.jet.lang.descriptors.TypeParameterDescriptor;
 import org.jetbrains.jet.lang.diagnostics.Diagnostic;
 import org.jetbrains.jet.lang.diagnostics.DiagnosticUtils;
-import org.jetbrains.jet.lang.diagnostics.UnresolvedReferenceDiagnosticFactory;
+import org.jetbrains.jet.lang.diagnostics.Errors;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.AnalyzerScriptParameter;
 import org.jetbrains.jet.lang.resolve.BindingContext;
@@ -160,7 +160,7 @@ public abstract class ExpectedResolveData {
 
         final Set<PsiElement> unresolvedReferences = Sets.newHashSet();
         for (Diagnostic diagnostic : bindingContext.getDiagnostics()) {
-            if (diagnostic.getFactory() instanceof UnresolvedReferenceDiagnosticFactory) {
+            if (Errors.UNRESOLVED_REFERENCE_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                 unresolvedReferences.add(diagnostic.getPsiElement());
             }
         }
diff --git a/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java b/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
index 0232bd788d5..138ea669557 100644
--- a/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
+++ b/idea/src/org/jetbrains/jet/plugin/highlighter/JetPsiChecker.java
@@ -35,7 +35,9 @@ import com.intellij.xml.util.XmlStringUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.TestOnly;
-import org.jetbrains.jet.lang.diagnostics.*;
+import org.jetbrains.jet.lang.diagnostics.Diagnostic;
+import org.jetbrains.jet.lang.diagnostics.Errors;
+import org.jetbrains.jet.lang.diagnostics.Severity;
 import org.jetbrains.jet.lang.diagnostics.rendering.DefaultErrorMessages;
 import org.jetbrains.jet.lang.psi.JetFile;
 import org.jetbrains.jet.lang.psi.JetReferenceExpression;
@@ -145,7 +147,7 @@ public class JetPsiChecker implements Annotator {
         if (!diagnostic.isValid()) return;
         List<TextRange> textRanges = diagnostic.getTextRanges();
         if (diagnostic.getSeverity() == Severity.ERROR) {
-            if (diagnostic.getFactory() instanceof UnresolvedReferenceDiagnosticFactory) {
+            if (Errors.UNRESOLVED_REFERENCE_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                 JetReferenceExpression referenceExpression = (JetReferenceExpression)diagnostic.getPsiElement();
                 PsiReference reference = referenceExpression.getReference();
                 if (reference instanceof MultiRangeReference) {
@@ -180,7 +182,7 @@ public class JetPsiChecker implements Annotator {
                 return;
             }
 
-            if (diagnostic.getFactory() instanceof RedeclarationDiagnosticFactory) {
+            if (Errors.REDECLARATION_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                 registerQuickFix(markRedeclaration(redeclarations, diagnostic, holder), diagnostic);
                 return;
             }
@@ -202,7 +204,7 @@ public class JetPsiChecker implements Annotator {
                 annotation.setTooltip(getMessage(diagnostic));
                 registerQuickFix(annotation, diagnostic);
 
-                if (diagnostic.getFactory() instanceof UnusedElementDiagnosticFactory) {
+                if (Errors.UNUSED_ELEMENT_DIAGNOSTICS.contains(diagnostic.getFactory())) {
                     annotation.setHighlightType(ProblemHighlightType.LIKE_UNUSED_SYMBOL);
                 }
             }