diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index 0aa482db4b4..3ab8cc82519 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -35,18 +35,10 @@ import java.util.*;
  * @author alex.tkachman
  */
 public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
-    private static final String CLASS_OBJECT = "java/lang/Object";
-    private static final String CLASS_STRING = "java/lang/String";
-    public static final String CLASS_STRING_BUILDER = "java/lang/StringBuilder";
-    private static final String CLASS_COMPARABLE = "java/lang/Comparable";
 
     private static final String CLASS_NO_PATTERN_MATCHED_EXCEPTION = "jet/NoPatternMatchedException";
     private static final String CLASS_TYPE_CAST_EXCEPTION = "jet/TypeCastException";
 
-    private static final Type OBJECT_TYPE = Type.getType(Object.class);
-    private static final Type THROWABLE_TYPE = Type.getType(Throwable.class);
-    private static final Type STRING_TYPE = Type.getObjectType(CLASS_STRING);
-
     private final Stack<Label> myContinueTargets = new Stack<Label>();
     private final Stack<Label> myBreakTargets = new Stack<Label>();
 
@@ -574,10 +566,10 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                             ? ((JetEscapeStringTemplateEntry) entry).getUnescapedValue()
                             : entry.getText();
                     v.aconst(text);
-                    invokeAppendMethod(STRING_TYPE);
+                    invokeAppendMethod(JetTypeMapper.JL_STRING_TYPE);
                 }
             }
-            v.invokevirtual(CLASS_STRING_BUILDER, "toString", "()Ljava/lang/String;");
+            v.invokevirtual("java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
             return StackValue.onStack(expressionType(expression));
         }
     }
@@ -972,7 +964,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 v.invokevirtual("jet/typeinfo/TypeInfo", "getClassObject", "()Ljava/lang/Object;");
                 v.checkcast(typeMapper.mapType(typeParameterDescriptor.getClassObjectType()));
 
-                return StackValue.onStack(OBJECT_TYPE);
+                return StackValue.onStack(JetTypeMapper.TYPE_OBJECT);
             }
             else {
                 // receiver
@@ -1693,7 +1685,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
 
     private StackValue generateNullSafeEquals(IElementType opToken, boolean leftNullable, boolean rightNullable) {
         if(!leftNullable) {
-            v.invokevirtual(CLASS_OBJECT, "equals", "(Ljava/lang/Object;)Z");
+            v.invokevirtual("java/lang/Object", "equals", "(Ljava/lang/Object;)Z");
             if (opToken == JetTokens.EXCLEQ) {
                 v.iconst(1);
                 v.xor(Type.INT_TYPE);
@@ -1706,7 +1698,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 v.ifnull(rightNull);
                 Label leftNull = new Label();
                 v.ifnull(leftNull);
-                v.invokevirtual(CLASS_OBJECT, "equals", "(Ljava/lang/Object;)Z");
+                v.invokevirtual("java/lang/Object", "equals", "(Ljava/lang/Object;)Z");
                 if (opToken == JetTokens.EXCLEQ || opToken == JetTokens.EXCLEQEQEQ) {
                     v.iconst(1);
                     v.xor(Type.INT_TYPE);
@@ -1731,7 +1723,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 v.pop();
                 Label leftNull = new Label();
                 v.ifnull(leftNull);
-                v.invokevirtual(CLASS_OBJECT, "equals", "(Ljava/lang/Object;)Z");
+                v.invokevirtual("java/lang/Object", "equals", "(Ljava/lang/Object;)Z");
                 if (opToken == JetTokens.EXCLEQ || opToken == JetTokens.EXCLEQEQEQ) {
                     v.iconst(1);
                     v.xor(Type.INT_TYPE);
@@ -1796,7 +1788,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
 
     private StackValue compareExpressionsOnStack(IElementType opToken, Type operandType) {
         if (operandType.getSort() == Type.OBJECT) {
-            v.invokeinterface(CLASS_COMPARABLE, "compareTo", "(Ljava/lang/Object;)I");
+            v.invokeinterface("java/lang/Comparable", "compareTo", "(Ljava/lang/Object;)I");
             v.iconst(0);
             operandType = Type.INT_TYPE;
         }
@@ -1865,7 +1857,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         v.anew(type);
         v.dup();
         Method method = new Method("<init>", Type.VOID_TYPE, new Type[0]);
-        v.invokespecial(CLASS_STRING_BUILDER, method.getName(), method.getDescriptor());
+        v.invokespecial("java/lang/StringBuilder", method.getName(), method.getDescriptor());
     }
 
     public void invokeAppend(final JetExpression expr) {
@@ -1885,7 +1877,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
     public void invokeAppendMethod(Type exprType) {
         Method appendDescriptor = new Method("append", JetTypeMapper.JL_STRING_BUILDER,
                 new Type[] { exprType.getSort() == Type.OBJECT ? JetTypeMapper.TYPE_OBJECT : exprType});
-        v.invokevirtual(CLASS_STRING_BUILDER, "append", appendDescriptor.getDescriptor());
+        v.invokevirtual("java/lang/StringBuilder", "append", appendDescriptor.getDescriptor());
     }
 
     @Override
@@ -2331,7 +2323,7 @@ If finally block is present, its last expression is the value of try expression.
             DeclarationDescriptor descriptor = jetType.getConstructor().getDeclarationDescriptor();
             if (descriptor instanceof ClassDescriptor || descriptor instanceof TypeParameterDescriptor) {
                 Type type = JetTypeMapper.boxType(typeMapper.mapType(jetType));
-                generateInstanceOf(StackValue.expression(OBJECT_TYPE, expression.getLeft(), this), jetType, true);
+                generateInstanceOf(StackValue.expression(JetTypeMapper.TYPE_OBJECT, expression.getLeft(), this), jetType, true);
                 Label isInstance = new Label();
                 v.ifne(isInstance);
                 v.pop();
@@ -2353,7 +2345,7 @@ If finally block is present, its last expression is the value of try expression.
 
     @Override
     public StackValue visitIsExpression(final JetIsExpression expression, StackValue receiver) {
-        final StackValue match = StackValue.expression(OBJECT_TYPE, expression.getLeftHandSide(), this);
+        final StackValue match = StackValue.expression(JetTypeMapper.TYPE_OBJECT, expression.getLeftHandSide(), this);
         return generatePatternMatch(expression.getPattern(), expression.isNegated(), match, null);
     }
 
@@ -2376,7 +2368,7 @@ If finally block is present, its last expression is the value of try expression.
             expressionToMatch.dupReceiver(v);
             expressionToMatch.put(subjectType, v);
             JetExpression condExpression = ((JetExpressionPattern) pattern).getExpression();
-            Type condType = isNumberPrimitive(subjectType) ? expressionType(condExpression) : OBJECT_TYPE;
+            Type condType = isNumberPrimitive(subjectType) ? expressionType(condExpression) : JetTypeMapper.TYPE_OBJECT;
             gen(condExpression, condType);
             return generateEqualsForExpressionsOnStack(JetTokens.EQEQ, subjectType, condType, false, false);
         }
@@ -2407,7 +2399,7 @@ If finally block is present, its last expression is the value of try expression.
         Label lblFail = new Label();
         Label lblDone = new Label();
         expressionToMatch.dupReceiver(v);
-        expressionToMatch.put(OBJECT_TYPE, v);
+        expressionToMatch.put(JetTypeMapper.TYPE_OBJECT, v);
         v.dup();
         final String tupleClassName = "jet/Tuple" + entries.size();
         Type tupleType = Type.getObjectType(tupleClassName);
@@ -2421,7 +2413,7 @@ If finally block is present, its last expression is the value of try expression.
 
         v.mark(lblCheck);
         for (int i = 0; i < entries.size(); i++) {
-            final StackValue tupleField = StackValue.field(OBJECT_TYPE, tupleClassName, "_" + (i + 1), false);
+            final StackValue tupleField = StackValue.field(JetTypeMapper.TYPE_OBJECT, tupleClassName, "_" + (i + 1), false);
             final StackValue stackValue = generatePatternMatch(entries.get(i).getPattern(), false, tupleField, nextEntry);
             stackValue.condJump(lblPopAndFail, true, v);
         }
@@ -2467,7 +2459,7 @@ If finally block is present, its last expression is the value of try expression.
     private void generateInstanceOf(StackValue expressionToGen, JetType jetType, boolean leaveExpressionOnStack) {
         DeclarationDescriptor descriptor = jetType.getConstructor().getDeclarationDescriptor();
         if (!hasTypeInfoForInstanceOf(jetType)) {
-            expressionToGen.put(OBJECT_TYPE, v);
+            expressionToGen.put(JetTypeMapper.TYPE_OBJECT, v);
             if (leaveExpressionOnStack) {
                 v.dup();
             }
@@ -2491,7 +2483,7 @@ If finally block is present, its last expression is the value of try expression.
         }
         else {
             generateTypeInfo(jetType);
-            expressionToGen.put(OBJECT_TYPE, v);
+            expressionToGen.put(JetTypeMapper.TYPE_OBJECT, v);
             if (leaveExpressionOnStack) {
                 v.dupX1();
             }
@@ -2718,7 +2710,7 @@ If finally block is present, its last expression is the value of try expression.
         v.dup();
         generateTypeInfo(new ProjectionErasingJetType(bindingContext.get(BindingContext.EXPRESSION_TYPE, expression)));
         for (JetExpression entry : entries) {
-            gen(entry, OBJECT_TYPE);
+            gen(entry, JetTypeMapper.TYPE_OBJECT);
         }
         v.invokespecial(className, "<init>", signature.toString());
         return StackValue.onStack(tupleType);
diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
index 2d97b6ede04..2e6bda3f6a3 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java
@@ -26,7 +26,7 @@ public class Concat implements IntrinsicMethod {
             codegen.invokeAppend(arguments.get(1));
         }
         
-        v.invokevirtual(ExpressionCodegen.CLASS_STRING_BUILDER, "toString", "()Ljava/lang/String;");
+        v.invokevirtual("java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
         return StackValue.onStack(Type.getObjectType("java/lang/String"));
     }
 }
diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/IntrinsicMethods.java b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/IntrinsicMethods.java
index 2edc35848db..75c951e3fe5 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/IntrinsicMethods.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/IntrinsicMethods.java
@@ -15,7 +15,6 @@ import org.jetbrains.jet.lang.types.JetStandardLibrary;
 import org.jetbrains.jet.lang.types.TypeProjection;
 import org.jetbrains.jet.plugin.JetFileType;
 import org.objectweb.asm.Opcodes;
-import sun.tools.tree.NewArrayExpression;
 
 import java.util.*;
 
@@ -87,7 +86,7 @@ public class IntrinsicMethods {
         declareOverload(myStdLib.getLibraryScope().getFunctions("identityEquals"), 1, EQUALS);
         declareOverload(myStdLib.getLibraryScope().getFunctions("plus"), 1, new StringPlus());
         declareOverload(myStdLib.getLibraryScope().getFunctions("Array"), 1, new NewArray());
-        declareOverload(myStdLib.getLibraryScope().getFunctions("npe"), 0, new NPE());
+        declareOverload(myStdLib.getLibraryScope().getFunctions("sure"), 0, new Sure());
 
         declareIntrinsicFunction("ByteIterator", "next", 0, ITERATOR_NEXT);
         declareIntrinsicFunction("ShortIterator", "next", 0, ITERATOR_NEXT);
diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/NPE.java b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Sure.java
similarity index 84%
rename from compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/NPE.java
rename to compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Sure.java
index c0bd922f973..0019fed155f 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/NPE.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Sure.java
@@ -13,11 +13,11 @@ import java.util.List;
 /**
  * @author alex.tkachman
  */
-public class NPE implements IntrinsicMethod {
+public class Sure implements IntrinsicMethod {
     @Override
     public StackValue generate(ExpressionCodegen codegen, InstructionAdapter v, Type expectedType, PsiElement element, List<JetExpression> arguments, StackValue receiver) {
         receiver.put(JetTypeMapper.TYPE_OBJECT, v);
-        v.invokestatic("jet/runtime/Intrinsics", "npe", "(Ljava/lang/Object;)Ljava/lang/Object;");
+        v.invokestatic("jet/runtime/Intrinsics", "sure", "(Ljava/lang/Object;)Ljava/lang/Object;");
         StackValue.onStack(JetTypeMapper.TYPE_OBJECT).put(expectedType, v);
         return StackValue.onStack(expectedType);
     }
diff --git a/compiler/frontend/src/jet/Library.jet b/compiler/frontend/src/jet/Library.jet
index f085b8012b2..888934c7121 100644
--- a/compiler/frontend/src/jet/Library.jet
+++ b/compiler/frontend/src/jet/Library.jet
@@ -42,7 +42,7 @@ fun Any?.equals(other : Any?) : Boolean// = this === other
 // Returns "null" for null
 fun Any?.toString() : String// = this === other
 
-fun <T : Any> T?.npe() : T
+fun <T : Any> T?.sure() : T
 
 fun String?.plus(other: Any?) : String
 
diff --git a/compiler/testData/checkerWithErrorTypes/quick/regressions/kt600.jet b/compiler/testData/checkerWithErrorTypes/quick/regressions/kt600.jet
index 6cebda6137c..0ca74ae5c33 100644
--- a/compiler/testData/checkerWithErrorTypes/quick/regressions/kt600.jet
+++ b/compiler/testData/checkerWithErrorTypes/quick/regressions/kt600.jet
@@ -1,9 +1,9 @@
 //KT-600 Problem with 'sure' extension function type inference
 // +JDK
 
-fun <T : Any> T?.sure() : T { if (this != null) return this else throw NullPointerException() }
+fun <T : Any> T?._sure() : T { if (this != null) return this else throw NullPointerException() }
 
 fun test() {
     val i : Int? = 10
-    val <!UNUSED_VARIABLE!>i2<!> : Int = i.sure() // inferred type is Int? but Int was excepted
+    val <!UNUSED_VARIABLE!>i2<!> : Int = i._sure() // inferred type is Int? but Int was excepted
 }
diff --git a/compiler/tests/org/jetbrains/jet/runtime/JetNpeTest.java b/compiler/tests/org/jetbrains/jet/runtime/JetNpeTest.java
index cf0ff45814a..51dd11b201b 100644
--- a/compiler/tests/org/jetbrains/jet/runtime/JetNpeTest.java
+++ b/compiler/tests/org/jetbrains/jet/runtime/JetNpeTest.java
@@ -1,7 +1,6 @@
 package org.jetbrains.jet.runtime;
 
 import jet.runtime.Intrinsics;
-import junit.framework.TestCase;
 import org.jetbrains.jet.codegen.CodegenTestCase;
 
 import java.lang.reflect.Method;
@@ -9,8 +8,8 @@ import java.lang.reflect.Method;
 public class JetNpeTest extends CodegenTestCase {
     public void testStackTrace () {
         try {
-            Intrinsics.npe(null);
-            fail("No NPE thrown");
+            Intrinsics.sure(null);
+            fail("No Sure thrown");
         }
         catch (NullPointerException e) {
             StackTraceElement stackTraceElement = e.getStackTrace()[0];
@@ -20,12 +19,13 @@ public class JetNpeTest extends CodegenTestCase {
     }
     
     public void testNotNull () throws Exception {
-        loadText("fun box() = if(10.npe() == 10) \"OK\" else \"fail\"");
+        loadText("fun box() = if(10.sure() == 10) \"OK\" else \"fail\"");
         blackBox();
     }
 
     public void testNull () throws Exception {
-        loadText("fun box() = if(null.npe() == 10) \"OK\" else \"fail\"");
+        loadText("fun box() = if(null.sure() == 10) \"OK\" else \"fail\"");
+        System.out.println(generateToText());
         Method box = generateFunction("box");
         assertThrows(box, NullPointerException.class, null);
     }
diff --git a/stdlib/src/jet/runtime/Intrinsics.java b/stdlib/src/jet/runtime/Intrinsics.java
index 9f26a0f72b5..1011e0ea2a7 100644
--- a/stdlib/src/jet/runtime/Intrinsics.java
+++ b/stdlib/src/jet/runtime/Intrinsics.java
@@ -1,5 +1,7 @@
 package jet.runtime;
 
+import java.util.ArrayList;
+
 /**
  * @author alex.tkachman
  */
@@ -11,7 +13,7 @@ public class Intrinsics {
         return ((self == null) ? "null" : self) + ((other == null) ? "null" : other.toString());
     }
 
-    public static Object npe(Object self) {
+    public static Object sure(Object self) {
         if(self == null)
             return throwNpe();
         return self;
@@ -20,4 +22,30 @@ public class Intrinsics {
     private static Object throwNpe() {
         throw new JetNullPointerException();
     }
+
+    private static Throwable sanitizeStackTrace(Throwable throwable) {
+        StackTraceElement[] stackTrace = throwable.getStackTrace();
+        ArrayList<StackTraceElement> list = new ArrayList<StackTraceElement>();
+        boolean skip = true;
+        for(StackTraceElement ste : stackTrace) {
+            if(!skip) {
+                list.add(ste);
+            }
+            else {
+                if("jet.runtime.Intrinsics".equals(ste.getClassName()) && "sure".equals(ste.getMethodName())) {
+                    skip = false;
+                }
+            }
+        }
+        throwable.setStackTrace(list.toArray(new StackTraceElement[list.size()]));
+        return throwable;
+    }
+
+    private static class JetNullPointerException extends NullPointerException {
+        @Override
+        public synchronized Throwable fillInStackTrace() {
+            super.fillInStackTrace();
+            return sanitizeStackTrace(this);
+        }
+    }
 }
diff --git a/stdlib/src/jet/runtime/JetNullPointerException.java b/stdlib/src/jet/runtime/JetNullPointerException.java
deleted file mode 100644
index ec9c6a0c1d5..00000000000
--- a/stdlib/src/jet/runtime/JetNullPointerException.java
+++ /dev/null
@@ -1,32 +0,0 @@
-package jet.runtime;
-
-import java.util.ArrayList;
-
-/**
-* @author alex.tkachman
-*/
-class JetNullPointerException extends NullPointerException {
-    @Override
-    public synchronized Throwable fillInStackTrace() {
-        super.fillInStackTrace();
-        StackTraceElement[] stackTrace = getStackTrace();
-        ArrayList<StackTraceElement> list = new ArrayList<StackTraceElement>();
-        boolean skip = true;
-        for(StackTraceElement ste : stackTrace) {
-            if(!skip) {
-                list.add(ste);
-            }
-            else {
-                if("jet.runtime.Intrinsics".equals(ste.getClassName()) && "npe".equals(ste.getMethodName())) {
-                    skip = false;
-                }
-            }
-        }
-        setStackTrace(list.toArray(new StackTraceElement[list.size()]));
-        return this;
-    }
-
-    public static void main(String[] args) {
-        Intrinsics.npe(null);
-    }
-}