diff --git a/idea/src/org/jetbrains/jet/lang/CollectingErrorHandler.java b/idea/src/org/jetbrains/jet/lang/CollectingErrorHandler.java
new file mode 100644
index 00000000000..f28dd05c061
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/lang/CollectingErrorHandler.java
@@ -0,0 +1,55 @@
+package org.jetbrains.jet.lang;
+
+import com.google.common.collect.Lists;
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
+import org.jetbrains.jet.lang.psi.JetExpression;
+import org.jetbrains.jet.lang.psi.JetReferenceExpression;
+import org.jetbrains.jet.lang.types.JetType;
+
+import java.util.List;
+
+/**
+ * @author abreslav
+ */
+public class CollectingErrorHandler extends ErrorHandler {
+    private final List<JetDiagnostic> diagnostics;
+
+    public CollectingErrorHandler() {
+        this(Lists.<JetDiagnostic>newArrayList());
+    }
+
+    public CollectingErrorHandler(List<JetDiagnostic> diagnostics) {
+        this.diagnostics = diagnostics;
+    }
+
+    public List<JetDiagnostic> getDiagnostics() {
+        return diagnostics;
+    }
+
+    @Override
+    public void unresolvedReference(@NotNull JetReferenceExpression referenceExpression) {
+        diagnostics.add(new JetDiagnostic.UnresolvedReferenceError(referenceExpression));
+    }
+
+    @Override
+    public void typeMismatch(@NotNull JetExpression expression, @NotNull JetType expectedType, @NotNull JetType actualType) {
+        diagnostics.add(new JetDiagnostic.TypeMismatchError(expression, expectedType, actualType));
+    }
+
+    @Override
+    public void redeclaration(@NotNull DeclarationDescriptor existingDescriptor, @NotNull DeclarationDescriptor redeclaredDescriptor) {
+        diagnostics.add(new JetDiagnostic.RedeclarationError(existingDescriptor, redeclaredDescriptor));
+    }
+
+    @Override
+    public void genericError(@NotNull ASTNode node, @NotNull String errorMessage) {
+        diagnostics.add(new JetDiagnostic.GenericError(node, errorMessage));
+    }
+
+    @Override
+    public void genericWarning(@NotNull ASTNode node, @NotNull String message) {
+        diagnostics.add(new JetDiagnostic.GenericWarning(node, message));
+    }
+}
diff --git a/idea/src/org/jetbrains/jet/lang/ErrorHandlerAdapter.java b/idea/src/org/jetbrains/jet/lang/ErrorHandlerAdapter.java
new file mode 100644
index 00000000000..ba2461c11e6
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/lang/ErrorHandlerAdapter.java
@@ -0,0 +1,44 @@
+package org.jetbrains.jet.lang;
+
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
+import org.jetbrains.jet.lang.psi.JetExpression;
+import org.jetbrains.jet.lang.psi.JetReferenceExpression;
+import org.jetbrains.jet.lang.types.JetType;
+
+/**
+ * @author abreslav
+ */
+public class ErrorHandlerAdapter extends ErrorHandler {
+    protected ErrorHandler worker;
+
+    public ErrorHandlerAdapter(ErrorHandler worker) {
+        this.worker = worker;
+    }
+
+    @Override
+    public void unresolvedReference(@NotNull JetReferenceExpression referenceExpression) {
+        worker.unresolvedReference(referenceExpression);
+    }
+
+    @Override
+    public void typeMismatch(@NotNull JetExpression expression, @NotNull JetType expectedType, @NotNull JetType actualType) {
+        worker.typeMismatch(expression, expectedType, actualType);
+    }
+
+    @Override
+    public void redeclaration(@NotNull DeclarationDescriptor existingDescriptor, @NotNull DeclarationDescriptor redeclaredDescriptor) {
+        worker.redeclaration(existingDescriptor, redeclaredDescriptor);
+    }
+
+    @Override
+    public void genericError(@NotNull ASTNode node, @NotNull String errorMessage) {
+        worker.genericError(node, errorMessage);
+    }
+
+    @Override
+    public void genericWarning(@NotNull ASTNode node, @NotNull String message) {
+        worker.genericWarning(node, message);
+    }
+}
diff --git a/idea/src/org/jetbrains/jet/lang/ErrorHandlerWithRegions.java b/idea/src/org/jetbrains/jet/lang/ErrorHandlerWithRegions.java
new file mode 100644
index 00000000000..92b39db5a62
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/lang/ErrorHandlerWithRegions.java
@@ -0,0 +1,97 @@
+package org.jetbrains.jet.lang;
+
+import com.intellij.lang.ASTNode;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
+import org.jetbrains.jet.lang.psi.JetExpression;
+import org.jetbrains.jet.lang.psi.JetReferenceExpression;
+import org.jetbrains.jet.lang.resolve.AnalyzingUtils;
+import org.jetbrains.jet.lang.types.JetType;
+
+import java.util.Stack;
+
+/**
+ * @author abreslav
+ */
+public class ErrorHandlerWithRegions extends ErrorHandler {
+
+    public class DiagnosticsRegion {
+        private final CollectingErrorHandler errorHandler;
+        private boolean committed = false;
+
+        private DiagnosticsRegion(CollectingErrorHandler errorHandler) {
+            this.errorHandler = errorHandler;
+        }
+
+        public CollectingErrorHandler getErrorHandler() {
+            assert !committed;
+            return errorHandler;
+        }
+
+        public void commit() {
+            assert !committed;
+            AnalyzingUtils.applyHandler(parent, errorHandler.getDiagnostics());
+            committed = true;
+        }
+    }
+
+    private final ErrorHandler parent;
+    private final Stack<CollectingErrorHandler> workers;
+    private ErrorHandler worker;
+
+    public ErrorHandlerWithRegions(ErrorHandler parent) {
+        this.parent = parent;
+        this.worker = parent;
+        this.workers = new Stack<CollectingErrorHandler>();
+    }
+
+    public void openRegion() {
+        CollectingErrorHandler newWorker = new CollectingErrorHandler();
+        workers.push(newWorker);
+        worker = newWorker;
+    }
+
+    public void closeAndCommitCurrentRegion() {
+        assert !workers.isEmpty();
+        CollectingErrorHandler region = workers.pop();
+        AnalyzingUtils.applyHandler(parent, region.getDiagnostics());
+
+        setWorker();
+    }
+
+    public DiagnosticsRegion closeAndReturnCurrentRegion() {
+        assert !workers.isEmpty();
+        CollectingErrorHandler currentWorker = workers.pop();
+        setWorker();
+        return new DiagnosticsRegion(currentWorker);
+    }
+
+    private void setWorker() {
+        worker = workers.isEmpty() ? parent : workers.peek();
+    }
+
+    @Override
+    public void unresolvedReference(@NotNull JetReferenceExpression referenceExpression) {
+        worker.unresolvedReference(referenceExpression);
+    }
+
+    @Override
+    public void typeMismatch(@NotNull JetExpression expression, @NotNull JetType expectedType, @NotNull JetType actualType) {
+        worker.typeMismatch(expression, expectedType, actualType);
+    }
+
+    @Override
+    public void redeclaration(@NotNull DeclarationDescriptor existingDescriptor, @NotNull DeclarationDescriptor redeclaredDescriptor) {
+        worker.redeclaration(existingDescriptor, redeclaredDescriptor);
+    }
+
+    @Override
+    public void genericError(@NotNull ASTNode node, @NotNull String errorMessage) {
+        worker.genericError(node, errorMessage);
+    }
+
+    @Override
+    public void genericWarning(@NotNull ASTNode node, @NotNull String message) {
+        worker.genericWarning(node, message);
+    }
+}
diff --git a/idea/src/org/jetbrains/jet/lang/JetHighlighter.java b/idea/src/org/jetbrains/jet/lang/JetHighlighter.java
index 8689d26f881..74b9383970c 100644
--- a/idea/src/org/jetbrains/jet/lang/JetHighlighter.java
+++ b/idea/src/org/jetbrains/jet/lang/JetHighlighter.java
@@ -7,6 +7,7 @@ import com.intellij.lexer.Lexer;
 import com.intellij.openapi.editor.HighlighterColors;
 import com.intellij.openapi.editor.SyntaxHighlighterColors;
 import com.intellij.openapi.editor.colors.TextAttributesKey;
+import com.intellij.openapi.editor.markup.TextAttributes;
 import com.intellij.openapi.fileTypes.SyntaxHighlighterBase;
 import com.intellij.psi.TokenType;
 import com.intellij.psi.tree.IElementType;
@@ -14,6 +15,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lexer.JetLexer;
 import org.jetbrains.jet.lexer.JetTokens;
 
+import java.awt.*;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -54,7 +56,7 @@ public class JetHighlighter extends SyntaxHighlighterBase {
                                                  SyntaxHighlighterColors.NUMBER.getDefaultAttributes()
                                                 );
 
-    private static final TextAttributesKey JET_STRING = TextAttributesKey.createTextAttributesKey(
+    public static final TextAttributesKey JET_STRING = TextAttributesKey.createTextAttributesKey(
                                                  "JET.STRING",
                                                  SyntaxHighlighterColors.STRING.getDefaultAttributes()
                                                 );
@@ -69,6 +71,14 @@ public class JetHighlighter extends SyntaxHighlighterBase {
                                                     HighlighterColors.BAD_CHARACTER.getDefaultAttributes()
                                                   );
 
+    public static final TextAttributesKey JET_AUTO_CAST_EXPRESSION;
+    static {
+        TextAttributes clone = SyntaxHighlighterColors.STRING.getDefaultAttributes().clone();
+        clone.setFontType(Font.PLAIN);
+// TODO: proper attributes
+        JET_AUTO_CAST_EXPRESSION = TextAttributesKey.createTextAttributesKey("JET.AUTO.CAST.EXPRESSION", clone);
+    }
+
     @NotNull
     public Lexer getHighlightingLexer() {
         return new JetLexer();
diff --git a/idea/src/org/jetbrains/jet/lang/annotations/JetPsiChecker.java b/idea/src/org/jetbrains/jet/lang/annotations/JetPsiChecker.java
index 0fa820c8637..98cf1b16184 100644
--- a/idea/src/org/jetbrains/jet/lang/annotations/JetPsiChecker.java
+++ b/idea/src/org/jetbrains/jet/lang/annotations/JetPsiChecker.java
@@ -88,6 +88,22 @@ public class JetPsiChecker implements Annotator {
                 AnalyzingUtils.applyHandler(errorHandler, bindingContext);
 
                 highlightBackingFields(holder, file, bindingContext);
+
+                file.acceptChildren(new JetVisitor() {
+                    @Override
+                    public void visitExpression(JetExpression expression) {
+                        JetType autoCast = bindingContext.getAutoCastType(expression);
+                        if (autoCast != null) {
+                            holder.createInfoAnnotation(expression, "Automatically cast to " + autoCast).setTextAttributes(JetHighlighter.JET_AUTO_CAST_EXPRESSION);
+                        }
+                        expression.acceptChildren(this);
+                    }
+
+                    @Override
+                    public void visitJetElement(JetElement element) {
+                        element.acceptChildren(this);
+                    }
+                });
             }
             catch (ProcessCanceledException e) {
                 throw e;
diff --git a/idea/src/org/jetbrains/jet/lang/resolve/AnalyzingUtils.java b/idea/src/org/jetbrains/jet/lang/resolve/AnalyzingUtils.java
index cee68e71770..f70838fcbf8 100644
--- a/idea/src/org/jetbrains/jet/lang/resolve/AnalyzingUtils.java
+++ b/idea/src/org/jetbrains/jet/lang/resolve/AnalyzingUtils.java
@@ -22,6 +22,7 @@ import org.jetbrains.jet.lang.psi.JetNamespace;
 import org.jetbrains.jet.lang.resolve.java.JavaPackageScope;
 import org.jetbrains.jet.lang.resolve.java.JavaSemanticServices;
 
+import java.util.Collection;
 import java.util.Collections;
 
 /**
@@ -115,7 +116,12 @@ public class AnalyzingUtils {
     }
 
     public static void applyHandler(@NotNull ErrorHandler errorHandler, @NotNull BindingContext bindingContext) {
-        for (JetDiagnostic jetDiagnostic : bindingContext.getDiagnostics()) {
+        Collection<JetDiagnostic> diagnostics = bindingContext.getDiagnostics();
+        applyHandler(errorHandler, diagnostics);
+    }
+
+    public static void applyHandler(@NotNull ErrorHandler errorHandler, @NotNull Collection<JetDiagnostic> diagnostics) {
+        for (JetDiagnostic jetDiagnostic : diagnostics) {
             jetDiagnostic.acceptHandler(errorHandler);
         }
     }
diff --git a/idea/src/org/jetbrains/jet/lang/resolve/BindingContext.java b/idea/src/org/jetbrains/jet/lang/resolve/BindingContext.java
index 910f0c60e76..bd2c1eb4d7a 100644
--- a/idea/src/org/jetbrains/jet/lang/resolve/BindingContext.java
+++ b/idea/src/org/jetbrains/jet/lang/resolve/BindingContext.java
@@ -1,6 +1,8 @@
 package org.jetbrains.jet.lang.resolve;
 
 import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.JetDiagnostic;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.psi.*;
@@ -41,5 +43,8 @@ public interface BindingContext {
 
     ConstructorDescriptor resolveSuperConstructor(JetDelegatorToSuperCall superCall);
 
+    @Nullable
+    JetType getAutoCastType(@NotNull JetExpression expression);
+
     Collection<JetDiagnostic> getDiagnostics();
 }
diff --git a/idea/src/org/jetbrains/jet/lang/resolve/BindingTrace.java b/idea/src/org/jetbrains/jet/lang/resolve/BindingTrace.java
index 46e2c1db7c0..a1c1d3ef006 100644
--- a/idea/src/org/jetbrains/jet/lang/resolve/BindingTrace.java
+++ b/idea/src/org/jetbrains/jet/lang/resolve/BindingTrace.java
@@ -2,7 +2,7 @@ package org.jetbrains.jet.lang.resolve;
 
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.jet.lang.ErrorHandler;
+import org.jetbrains.jet.lang.ErrorHandlerWithRegions;
 import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
 import org.jetbrains.jet.lang.descriptors.PropertyDescriptor;
 import org.jetbrains.jet.lang.psi.*;
@@ -35,8 +35,10 @@ public interface BindingTrace {
 
     void requireBackingField(@NotNull PropertyDescriptor propertyDescriptor);
 
+    void recordAutoCast(@NotNull JetExpression expression, @NotNull JetType type);
+
     @NotNull
-    ErrorHandler getErrorHandler();
+    ErrorHandlerWithRegions getErrorHandler();
 
     boolean isProcessed(@NotNull JetExpression expression);
 
diff --git a/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceAdapter.java b/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceAdapter.java
index 423961c8998..fa6986bf320 100644
--- a/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceAdapter.java
+++ b/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceAdapter.java
@@ -2,7 +2,7 @@ package org.jetbrains.jet.lang.resolve;
 
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.jet.lang.ErrorHandler;
+import org.jetbrains.jet.lang.ErrorHandlerWithRegions;
 import org.jetbrains.jet.lang.descriptors.DeclarationDescriptor;
 import org.jetbrains.jet.lang.descriptors.PropertyDescriptor;
 import org.jetbrains.jet.lang.psi.*;
@@ -14,6 +14,11 @@ import org.jetbrains.jet.lang.types.JetType;
 public class BindingTraceAdapter implements BindingTrace {
     private final BindingTrace originalTrace;
 
+    @Override
+    public void recordAutoCast(@NotNull JetExpression expression, @NotNull JetType type) {
+        originalTrace.recordAutoCast(expression, type);
+    }
+
     public BindingTraceAdapter(BindingTrace originalTrace) {
         this.originalTrace = originalTrace;
     }
@@ -63,7 +68,7 @@ public class BindingTraceAdapter implements BindingTrace {
 
     @NotNull
     @Override
-    public ErrorHandler getErrorHandler() {
+    public ErrorHandlerWithRegions getErrorHandler() {
         return originalTrace.getErrorHandler();
     }
 
diff --git a/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceContext.java b/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceContext.java
index d170dd17fcc..84bf464b244 100644
--- a/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceContext.java
+++ b/idea/src/org/jetbrains/jet/lang/resolve/BindingTraceContext.java
@@ -3,11 +3,11 @@ package org.jetbrains.jet.lang.resolve;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
-import com.intellij.lang.ASTNode;
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.jetbrains.jet.lang.ErrorHandler;
+import org.jetbrains.jet.lang.CollectingErrorHandler;
+import org.jetbrains.jet.lang.ErrorHandlerWithRegions;
 import org.jetbrains.jet.lang.JetDiagnostic;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.psi.*;
@@ -32,39 +32,15 @@ public class BindingTraceContext implements BindingContext, BindingTrace {
     private final Set<JetElement> statements = new HashSet<JetElement>();
     private final Set<PropertyDescriptor> backingFieldRequired = new HashSet<PropertyDescriptor>();
     private final Set<JetExpression> processed = Sets.newHashSet();
+    private final Map<JetExpression, JetType> autoCasts = Maps.newHashMap();
 
-    private Collection<JetDiagnostic> diagnostics = Lists.newArrayList();
-    private ErrorHandler errorHandler = new ErrorHandler() {
-        @Override
-        public void unresolvedReference(@NotNull JetReferenceExpression referenceExpression) {
-            diagnostics.add(new JetDiagnostic.UnresolvedReferenceError(referenceExpression));
-        }
-
-        @Override
-        public void typeMismatch(@NotNull JetExpression expression, @NotNull JetType expectedType, @NotNull JetType actualType) {
-            diagnostics.add(new JetDiagnostic.TypeMismatchError(expression, expectedType, actualType));
-        }
-
-        @Override
-        public void redeclaration(@NotNull DeclarationDescriptor existingDescriptor, @NotNull DeclarationDescriptor redeclaredDescriptor) {
-            diagnostics.add(new JetDiagnostic.RedeclarationError(existingDescriptor, redeclaredDescriptor));
-        }
-
-        @Override
-        public void genericError(@NotNull ASTNode node, @NotNull String errorMessage) {
-            diagnostics.add(new JetDiagnostic.GenericError(node, errorMessage));
-        }
-
-        @Override
-        public void genericWarning(@NotNull ASTNode node, @NotNull String message) {
-            diagnostics.add(new JetDiagnostic.GenericWarning(node, message));
-        }
-    };
+    private final List<JetDiagnostic> diagnostics = Lists.newArrayList();
+    private final ErrorHandlerWithRegions errorHandler = new ErrorHandlerWithRegions(new CollectingErrorHandler(diagnostics));
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
     @NotNull
-    public ErrorHandler getErrorHandler() {
+    public ErrorHandlerWithRegions getErrorHandler() {
         return errorHandler;
     }
 
@@ -133,6 +109,11 @@ public class BindingTraceContext implements BindingContext, BindingTrace {
         backingFieldRequired.add(propertyDescriptor);
     }
 
+    @Override
+    public void recordAutoCast(@NotNull JetExpression expression, @NotNull JetType type) {
+        safePut(autoCasts, expression, type);
+    }
+
     @Override
     public void recordBlock(JetFunctionLiteralExpression expression) {
         blocks.add(expression);
@@ -281,6 +262,11 @@ public class BindingTraceContext implements BindingContext, BindingTrace {
         return descriptor instanceof ConstructorDescriptor ? (ConstructorDescriptor) descriptor : null;
     }
 
+    @Override
+    public JetType getAutoCastType(@NotNull JetExpression expression) {
+        return autoCasts.get(expression);
+    }
+
     @Override
     public Collection<JetDiagnostic> getDiagnostics() {
         return diagnostics;
diff --git a/idea/src/org/jetbrains/jet/lang/types/DataFlowInfo.java b/idea/src/org/jetbrains/jet/lang/types/DataFlowInfo.java
index c78ce25faed..7a150bf0a89 100644
--- a/idea/src/org/jetbrains/jet/lang/types/DataFlowInfo.java
+++ b/idea/src/org/jetbrains/jet/lang/types/DataFlowInfo.java
@@ -14,10 +14,10 @@ import java.util.*;
 public class DataFlowInfo {
 
     private static DataFlowInfo EMPTY = new DataFlowInfo(ImmutableMap.<VariableDescriptor, NullabilityFlags>of(), Multimaps.forMap(Collections.<VariableDescriptor, JetType>emptyMap()));
-    public static final Supplier<SortedSet<JetType>> SORTED_SET_SUPPLIER = new Supplier<SortedSet<JetType>>() {
+        public static final Supplier<List<JetType>> ARRAY_LIST_SUPPLIER = new Supplier<List<JetType>>() {
         @Override
-        public SortedSet<JetType> get() {
-            return new TreeSet<JetType>();
+        public List<JetType> get() {
+            return Lists.newArrayList();
         }
     };
 
@@ -83,7 +83,7 @@ public class DataFlowInfo {
     public DataFlowInfo isInstanceOf(@NotNull VariableDescriptor variableDescriptor, @NotNull JetType type) {
         Multimap<VariableDescriptor, JetType> newTypeInfo = copyTypeInfo();
         newTypeInfo.put(variableDescriptor, type);
-        return new DataFlowInfo(getEqualsToNullMap(variableDescriptor, false), newTypeInfo);
+        return new DataFlowInfo(getEqualsToNullMap(variableDescriptor, !type.isNullable()), newTypeInfo);
     }
 
     public DataFlowInfo and(DataFlowInfo other) {
@@ -107,7 +107,7 @@ public class DataFlowInfo {
     }
 
     private Multimap<VariableDescriptor, JetType> copyTypeInfo() {
-        Multimap<VariableDescriptor, JetType> newTypeInfo = Multimaps.newSortedSetMultimap(Maps.<VariableDescriptor, Collection<JetType>>newHashMap(), SORTED_SET_SUPPLIER);
+        Multimap<VariableDescriptor, JetType> newTypeInfo = Multimaps.newListMultimap(Maps.<VariableDescriptor, Collection<JetType>>newHashMap(), ARRAY_LIST_SUPPLIER);
         newTypeInfo.putAll(typeInfo);
         return newTypeInfo;
     }
diff --git a/idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java b/idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java
index abba6650322..c92354a6ee8 100644
--- a/idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java
+++ b/idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java
@@ -10,6 +10,7 @@ import com.intellij.psi.tree.IElementType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.JetNodeTypes;
+import org.jetbrains.jet.lang.ErrorHandlerWithRegions;
 import org.jetbrains.jet.lang.JetSemanticServices;
 import org.jetbrains.jet.lang.cfg.JetFlowInformationProvider;
 import org.jetbrains.jet.lang.descriptors.*;
@@ -1346,12 +1347,14 @@ public class JetTypeInferrer {
             condition.accept(new JetVisitor() {
                 @Override
                 public void visitIsExpression(JetIsExpression expression) {
-                    VariableDescriptor variableDescriptor = getVariableDescriptorFromSimpleName(expression.getLeftHandSide());
-                    if (variableDescriptor != null) {
-                        JetPattern pattern = expression.getPattern();
-                        if (pattern instanceof JetTypePattern) {
-                            JetTypePattern jetTypePattern = (JetTypePattern) pattern;
-                            result[0] = dataFlowInfo.isInstanceOf(variableDescriptor, trace.getBindingContext().resolveTypeReference(jetTypePattern.getTypeReference()));
+                    if (conditionValue) {
+                        VariableDescriptor variableDescriptor = getVariableDescriptorFromSimpleName(expression.getLeftHandSide());
+                        if (variableDescriptor != null) {
+                            JetPattern pattern = expression.getPattern();
+                            if (pattern instanceof JetTypePattern) {
+                                JetTypePattern jetTypePattern = (JetTypePattern) pattern;
+                                result[0] = dataFlowInfo.isInstanceOf(variableDescriptor, trace.getBindingContext().resolveTypeReference(jetTypePattern.getTypeReference()));
+                            }
                         }
                     }
                 }
@@ -1642,25 +1645,37 @@ public class JetTypeInferrer {
             JetExpression receiverExpression = expression.getReceiverExpression();
             JetType receiverType = new TypeInferrerVisitorWithNamespaces(scope, false, dataFlowInfo).getType(receiverExpression);
             if (receiverType != null) {
+                ErrorHandlerWithRegions errorHandler = trace.getErrorHandler();
+                errorHandler.openRegion();
                 JetType selectorReturnType = getSelectorReturnType(receiverType, selectorExpression);
-                
-                if (selectorReturnType == null) {
+
+                if (selectorReturnType != null) {
+                    errorHandler.closeAndCommitCurrentRegion();
+                }
+                else {
+                    ErrorHandlerWithRegions.DiagnosticsRegion regionToCommit = errorHandler.closeAndReturnCurrentRegion();
+
                     VariableDescriptor variableDescriptor = getVariableDescriptorFromSimpleName(receiverExpression);
                     if (variableDescriptor != null) {
                         Collection<JetType> possibleTypes = dataFlowInfo.getPossibleTypes(variableDescriptor);
                         for (JetType possibleType : possibleTypes) {
+                            errorHandler.openRegion();
                             selectorReturnType = getSelectorReturnType(possibleType, selectorExpression);
                             if (selectorReturnType != null) {
+                                regionToCommit = errorHandler.closeAndReturnCurrentRegion();
+                                trace.recordAutoCast(receiverExpression, possibleType);
                                 break;
                             }
                         }
                     }
+
+                    regionToCommit.commit();
                 }
 
                 if (expression.getOperationSign() == JetTokens.QUEST) {
                     if (selectorReturnType != null && !isBoolean(selectorReturnType) && selectorExpression != null) {
                         // TODO : more comprehensible error message
-                        trace.getErrorHandler().typeMismatch(selectorExpression, semanticServices.getStandardLibrary().getBooleanType(), selectorReturnType);
+                        errorHandler.typeMismatch(selectorExpression, semanticServices.getStandardLibrary().getBooleanType(), selectorReturnType);
                     }
                     result = TypeUtils.makeNullable(receiverType);
                 }
diff --git a/idea/testData/checker/infos/Autocasts.jet b/idea/testData/checker/infos/Autocasts.jet
new file mode 100644
index 00000000000..b1b7d3f3bfe
--- /dev/null
+++ b/idea/testData/checker/infos/Autocasts.jet
@@ -0,0 +1,41 @@
+class A() {
+  fun foo() {}
+}
+
+class B() : A() {
+  fun bar() {}
+}
+
+fun f9() {
+  val a : A?
+  a?.foo()
+  a?.<error>bar</error>()
+  if (a is B) {
+    <info descr="Automatically cast to B">a</info>.bar()
+    a.foo()
+  }
+  a?.foo()
+  a?.<error>bar</error>()
+  if (!(a is B)) {
+    a?.<error>bar</error>()
+    a?.foo()
+  }
+  if (!(a is B) || <info descr="Automatically cast to B">a</info>.bar() == ()) {
+      a?.<error>bar</error>()
+  }
+  if (!(a is B)) {
+    return;
+  }
+  <info descr="Automatically cast to B">a</info>.bar()
+  a.foo()
+}
+
+fun f10() {
+  val a : A?
+  if (!(a is B)) {
+    return;
+  }
+  if (!(a is B)) {
+    return;
+  }
+}
diff --git a/idea/tests/org/jetbrains/jet/JetTestUtils.java b/idea/tests/org/jetbrains/jet/JetTestUtils.java
index 9944801a755..1649820cef3 100644
--- a/idea/tests/org/jetbrains/jet/JetTestUtils.java
+++ b/idea/tests/org/jetbrains/jet/JetTestUtils.java
@@ -3,6 +3,7 @@ package org.jetbrains.jet;
 import com.intellij.psi.PsiElement;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.ErrorHandler;
+import org.jetbrains.jet.lang.ErrorHandlerWithRegions;
 import org.jetbrains.jet.lang.JetDiagnostic;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.psi.*;
@@ -63,10 +64,15 @@ public class JetTestUtils {
         public void requireBackingField(@NotNull PropertyDescriptor propertyDescriptor) {
         }
 
+        @Override
+        public void recordAutoCast(@NotNull JetExpression expression, @NotNull JetType type) {
+
+        }
+
         @NotNull
         @Override
-        public ErrorHandler getErrorHandler() {
-            return ErrorHandler.DO_NOTHING;
+        public ErrorHandlerWithRegions getErrorHandler() {
+            return new ErrorHandlerWithRegions(ErrorHandler.DO_NOTHING);
         }
 
         @Override
@@ -178,6 +184,11 @@ public class JetTestUtils {
                     throw new UnsupportedOperationException(); // TODO
                 }
 
+                @Override
+                public JetType getAutoCastType(@NotNull JetExpression expression) {
+                    throw new UnsupportedOperationException(); // TODO
+                }
+
                 @Override
                 public Collection<JetDiagnostic> getDiagnostics() {
                     throw new UnsupportedOperationException(); // TODO