diff --git a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index 2930cd49f68..67e66415370 100644
--- a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -19,15 +19,21 @@ import java.util.Stack;
 public class ExpressionCodegen extends JetVisitor {
     private final Stack<Label> myLoopStarts = new Stack<Label>();
     private final Stack<Label> myLoopEnds = new Stack<Label>();
+    private final Stack<StackValue> myStack = new Stack<StackValue>();
 
     private final InstructionAdapter v;
     private final JetStandardLibrary stdlib;
     private final FrameMap myMap;
+    private final JetTypeMapper typeMapper;
+    private final Type returnType;
     private final BindingContext bindingContext;
 
-    public ExpressionCodegen(MethodVisitor v, BindingContext bindingContext, JetStandardLibrary stdlib, FrameMap myMap) {
+    public ExpressionCodegen(MethodVisitor v, BindingContext bindingContext, JetStandardLibrary stdlib, FrameMap myMap,
+                             JetTypeMapper typeMapper, Type returnType) {
         this.stdlib = stdlib;
         this.myMap = myMap;
+        this.typeMapper = typeMapper;
+        this.returnType = returnType;
         this.v = new InstructionAdapter(v);
         this.bindingContext = bindingContext;
     }
@@ -37,6 +43,15 @@ public class ExpressionCodegen extends JetVisitor {
         expr.accept(this);
     }
 
+    private void gen(JetElement expr, Type type) {
+        int oldStackDepth = myStack.size();
+        gen(expr);
+        if (myStack.size() == oldStackDepth+1) {
+            StackValue value = myStack.pop();
+            value.put(type, v);
+        }
+    }
+
     @Override
     public void visitExpression(JetExpression expression) {
         throw new UnsupportedOperationException("Codegen for " + expression + " is not yet implemented");
@@ -54,8 +69,9 @@ public class ExpressionCodegen extends JetVisitor {
 
     @Override
     public void visitIfExpression(JetIfExpression expression) {
-        gen(expression.getCondition());
-        unboxBoolean();
+        JetType expressionType = bindingContext.getExpressionType(expression);
+        Type asmType = typeMapper.mapType(expressionType);
+        gen(expression.getCondition(), Type.BOOLEAN_TYPE);
 
         JetExpression thenExpression = expression.getThen();
         JetExpression elseExpression = expression.getElse();
@@ -78,13 +94,13 @@ public class ExpressionCodegen extends JetVisitor {
         Label elseLabel = new Label();
         v.ifeq(elseLabel); // == 0, i.e. false
 
-        gen(thenExpression);
+        gen(thenExpression, asmType);
 
         Label endLabel = new Label();
         v.goTo(endLabel);
         v.mark(elseLabel);
 
-        gen(elseExpression);
+        gen(elseExpression, asmType);
 
         v.mark(endLabel);
     }
@@ -178,6 +194,8 @@ public class ExpressionCodegen extends JetVisitor {
 
     @Override
     public void visitConstantExpression(JetConstantExpression expression) {
+        myStack.push(StackValue.constant(expression.getValue()));
+        /*
         Object value = expression.getValue();
         v.aconst(value);
 
@@ -205,6 +223,7 @@ public class ExpressionCodegen extends JetVisitor {
         else if (value instanceof Double) {
             v.invokestatic("java/lang/Double", "valueOf", "(D)Ljava/lang/Double;");
         }
+        */
     }
 
     @Override
@@ -229,8 +248,11 @@ public class ExpressionCodegen extends JetVisitor {
         for (JetElement statement : statements) {
             if (statement instanceof JetProperty) {
                 JetProperty var = (JetProperty) statement;
-                int index = myMap.leave(bindingContext.getPropertyDescriptor(var));
-                v.visitLocalVariable(var.getName(), getType(var).getDescriptor(), null, blockStart, blockEnd, index);
+                PropertyDescriptor propertyDescriptor = bindingContext.getPropertyDescriptor(var);
+                Type outType = typeMapper.mapType(propertyDescriptor.getOutType());
+
+                int index = myMap.leave(propertyDescriptor);
+                v.visitLocalVariable(var.getName(), outType.getDescriptor(), null, blockStart, blockEnd, index);
             }
         }
 
@@ -240,14 +262,22 @@ public class ExpressionCodegen extends JetVisitor {
     public void visitReturnExpression(JetReturnExpression expression) {
         final JetExpression returnedExpression = expression.getReturnedExpression();
         if (returnedExpression != null) {
-            returnedExpression.accept(this);
-            v.visitInsn(Opcodes.ARETURN);
+            gen(returnedExpression, returnType);
+            v.areturn(returnType);
         }
         else {
             v.visitInsn(Opcodes.RETURN);
         }
     }
 
+    public void returnTopOfStack() {
+        if (myStack.size() > 0) {
+            StackValue value = myStack.pop();
+            value.put(returnType, v);
+            v.areturn(returnType);
+        }
+    }
+
     @Override
     public void visitSimpleNameExpression(JetSimpleNameExpression expression) {
         final DeclarationDescriptor descriptor = bindingContext.resolveReferenceExpression(expression);
@@ -267,7 +297,7 @@ public class ExpressionCodegen extends JetVisitor {
         else {
             int index = myMap.getIndex(descriptor);
             if (index >= 0) {
-                v.visitVarInsn(Opcodes.ALOAD, index);
+                myStack.push(StackValue.local(index, ((PropertyDescriptor) descriptor).getOutType()));
             }
             else {
                 throw new UnsupportedOperationException("don't know how to generate reference " + descriptor);
@@ -277,11 +307,6 @@ public class ExpressionCodegen extends JetVisitor {
 
     @Override
     public void visitCallExpression(JetCallExpression expression) {
-        List<JetArgument> args = expression.getValueArguments();
-        for (JetArgument arg : args) {
-            gen(arg.getArgumentExpression());
-        }
-
         JetExpression callee = expression.getCalleeExpression();
 
         if (callee instanceof JetSimpleNameExpression) {
@@ -290,6 +315,14 @@ public class ExpressionCodegen extends JetVisitor {
                 PsiElement declarationPsiElement = bindingContext.getDeclarationPsiElement(funDescriptor);
                 if (declarationPsiElement instanceof PsiMethod) {
                     PsiMethod method = (PsiMethod) declarationPsiElement;
+                    PsiParameter[] parameters = method.getParameterList().getParameters();
+
+                    List<JetArgument> args = expression.getValueArguments();
+                    for (int i = 0, argsSize = args.size(); i < argsSize; i++) {
+                        JetArgument arg = args.get(i);
+                        gen(arg.getArgumentExpression(), psiTypeToAsm(parameters [i].getType()));
+                    }
+
                     if (method.hasModifierProperty(PsiModifier.STATIC)) {
                         v.visitMethodInsn(Opcodes.INVOKESTATIC,
                                 jvmName(method.getContainingClass()),
@@ -302,7 +335,7 @@ public class ExpressionCodegen extends JetVisitor {
                                           method.getName(),
                                           getMethodDescriptor(method));
                     }
-                    boxIfNeeded(method.getReturnType());
+                    myStack.push(StackValue.onStack(psiTypeToAsm(method.getReturnType())));
                 }
             }
             else {
@@ -422,12 +455,10 @@ public class ExpressionCodegen extends JetVisitor {
                 if (op.getName().equals("plus")) {
                     JetType returnType = ((FunctionDescriptor) op).getUnsubstitutedReturnType();
                     if (returnType.equals(stdlib.getIntType())) {
-                        gen(expression.getLeft());
-                        unbox(PsiType.INT);
-                        gen(expression.getRight());
-                        unbox(PsiType.INT);
+                        gen(expression.getLeft(), Type.INT_TYPE);
+                        gen(expression.getRight(), Type.INT_TYPE);
                         v.add(Type.INT_TYPE);
-                        boxIfNeeded(PsiType.INT);
+                        myStack.push(StackValue.onStack(Type.INT_TYPE));
                         return;
                     }
                 }
@@ -436,24 +467,22 @@ public class ExpressionCodegen extends JetVisitor {
         throw new UnsupportedOperationException("Don't know how to generate binary op " + expression);
     }
 
-    private Type getType(JetProperty var) {
-        return InstructionAdapter.OBJECT_TYPE;  // TODO:
-    }
-
     private boolean isUnitType(JetExpression e) {
         return false; // TODO:!!!
     }
 
     @Override
     public void visitProperty(JetProperty property) {
-        int index = myMap.getIndex(bindingContext.getPropertyDescriptor(property));
+        PropertyDescriptor propertyDescriptor = bindingContext.getPropertyDescriptor(property);
+        int index = myMap.getIndex(propertyDescriptor);
 
         assert index >= 0;
 
         JetExpression initializer = property.getInitializer();
         if (initializer != null) {
-            gen(initializer);
-            v.store(index, getType(property));
+            Type type = typeMapper.mapType(propertyDescriptor.getOutType());
+            gen(initializer, type);
+            v.store(index, type);
         }
     }
 
diff --git a/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java b/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
index 833f89298ab..ec6d515e558 100644
--- a/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
@@ -56,20 +56,21 @@ public class FunctionCodegen {
             frameMap.enter(parameter);
         }
 
-        bodyExpression.accept(new ExpressionCodegen(mv, bindingContext, standardLibrary, frameMap));
-        generateReturn(mv, bodyExpression);
+        ExpressionCodegen codegen = new ExpressionCodegen(mv, bindingContext, standardLibrary, frameMap, typeMapper, returnType);
+        bodyExpression.accept(codegen);
+        generateReturn(mv, bodyExpression, codegen);
         mv.visitMaxs(0, 0);
         mv.visitEnd();
     }
 
-    private void generateReturn(MethodVisitor mv, JetExpression bodyExpression) {
+    private void generateReturn(MethodVisitor mv, JetExpression bodyExpression, ExpressionCodegen codegen) {
         if (!endsWithReturn(bodyExpression)) {
             final JetType expressionType = bindingContext.getExpressionType(bodyExpression);
             if (expressionType.equals(JetStandardClasses.getUnitType())) {
                 mv.visitInsn(Opcodes.RETURN);
             }
             else {
-                mv.visitInsn(Opcodes.ARETURN);
+                codegen.returnTopOfStack();
             }
         }
     }
diff --git a/idea/src/org/jetbrains/jet/codegen/JetTypeMapper.java b/idea/src/org/jetbrains/jet/codegen/JetTypeMapper.java
index 78696d5163a..09d76daa986 100644
--- a/idea/src/org/jetbrains/jet/codegen/JetTypeMapper.java
+++ b/idea/src/org/jetbrains/jet/codegen/JetTypeMapper.java
@@ -18,10 +18,13 @@ public class JetTypeMapper {
             return Type.VOID_TYPE;
         }
         if (jetType.equals(standardLibrary.getIntType())) {
-            return Type.getType(Integer.class);
+            return Type.INT_TYPE;
         }
         if (jetType.equals(standardLibrary.getLongType())) {
-            return Type.getType(Long.class);
+            return Type.LONG_TYPE;
+        }
+        if (jetType.equals(standardLibrary.getBooleanType())) {
+            return Type.BOOLEAN_TYPE;
         }
         if (jetType.equals(standardLibrary.getStringType())) {
             return Type.getType(String.class);
diff --git a/idea/src/org/jetbrains/jet/codegen/StackValue.java b/idea/src/org/jetbrains/jet/codegen/StackValue.java
new file mode 100644
index 00000000000..df855a340d7
--- /dev/null
+++ b/idea/src/org/jetbrains/jet/codegen/StackValue.java
@@ -0,0 +1,76 @@
+package org.jetbrains.jet.codegen;
+
+import org.jetbrains.jet.lang.types.JetType;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.commons.InstructionAdapter;
+
+/**
+ * @author yole
+ */
+public abstract class StackValue {
+    public abstract void put(Type type, InstructionAdapter v);
+
+    public static StackValue local(int index, JetType type) {
+        return new Local(index, type);
+    }
+
+    public static StackValue onStack(Type type) {
+        return new OnStack(type);
+    }
+
+    public static StackValue constant(Object value) {
+        return new Constant(value);
+    }
+
+    public static class Local extends StackValue {
+        private final int index;
+        private final JetType type;
+
+        public Local(int index, JetType type) {
+            this.index = index;
+            this.type = type;
+        }
+
+        @Override
+        public void put(Type type, InstructionAdapter v) {
+            v.load(index, type);
+            // TODO box/unbox
+        }
+    }
+
+    public static class OnStack extends StackValue {
+        private final Type type;
+
+        public OnStack(Type type) {
+            this.type = type;
+        }
+
+        @Override
+        public void put(Type type, InstructionAdapter v) {
+        }
+    }
+
+    public static class Constant extends StackValue {
+        private final Object value;
+
+        public Constant(Object value) {
+            this.value = value;
+        }
+
+        @Override
+        public void put(Type type, InstructionAdapter v) {
+            if (type == Type.INT_TYPE) {
+                if (value instanceof Number) {
+                    v.iconst(((Number) value).intValue());
+                }
+                else {
+                    throw new UnsupportedOperationException("don't know how to put this value");
+                }
+            }
+            // TODO other primitive types
+            else {
+                v.aconst(value);
+            }
+        }
+    }
+}
diff --git a/idea/testData/codegen/assign.jet b/idea/testData/codegen/assign.jet
new file mode 100644
index 00000000000..c552d47eb6c
--- /dev/null
+++ b/idea/testData/codegen/assign.jet
@@ -0,0 +1,5 @@
+fun f(): Int {
+  var x: Int = 1
+  x = x + 1
+  return x
+}
diff --git a/idea/testData/codegen/if.jet b/idea/testData/codegen/if.jet
new file mode 100644
index 00000000000..282a87e267b
--- /dev/null
+++ b/idea/testData/codegen/if.jet
@@ -0,0 +1 @@
+fun foo(b: Boolean): Int { return if (b) 15 else 20 }
\ No newline at end of file
diff --git a/idea/testData/codegen/singleBranchIf.jet b/idea/testData/codegen/singleBranchIf.jet
new file mode 100644
index 00000000000..29001194b38
--- /dev/null
+++ b/idea/testData/codegen/singleBranchIf.jet
@@ -0,0 +1,4 @@
+fun foo(b: Boolean) : Int {
+  if (b) return 15;
+  return 20;
+}
diff --git a/idea/testData/codegen/while.jet b/idea/testData/codegen/while.jet
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java b/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
index 08f44a730ba..c27030a9f7e 100644
--- a/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
@@ -3,6 +3,7 @@ package org.jetbrains.jet.codegen;
 import com.intellij.codeInsight.daemon.LightDaemonAnalyzerTestCase;
 import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.jet.lang.psi.JetProperty;
+import org.objectweb.asm.Type;
 import org.objectweb.asm.util.TraceMethodVisitor;
 
 import java.io.IOException;
@@ -13,36 +14,7 @@ import java.io.StringWriter;
  * @author max
  */
 public class ExpressionGenTest extends LightDaemonAnalyzerTestCase {
-    public void testIntegerZeroExpression() throws Exception {
-        checkCode("0",
-                "LDC 0\n" +
-                "INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;");
-    }
-
     public void testIf() throws Exception {
-        checkCode("if (false) 15 else 20",
-                "LDC false\n" +
-                "INVOKESTATIC java/lang/Boolean.valueOf (Z)Ljava/lang/Boolean;\n" +
-                "INVOKEVIRTUAL java/lang/Boolean.booleanValue ()Z\n" +
-                "IFEQ L0\n" +
-                "LDC 15\n" +
-                "INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;\n" +
-                "GOTO L1\n" +
-                "L0\n" +
-                "LDC 20\n" +
-                "INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;\n" +
-                "L1");
-
-        checkCode("if (false) 15",
-                "LDC false\n" +
-                "INVOKESTATIC java/lang/Boolean.valueOf (Z)Ljava/lang/Boolean;\n" +
-                "INVOKEVIRTUAL java/lang/Boolean.booleanValue ()Z\n" +
-                "IFEQ L0\n" +
-                "LDC 15\n" +
-                "INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;\n" +
-                "POP\n" +
-                "L0");
-
         checkCode("if (false) else 20",
                 "LDC false\n" +
                 "INVOKESTATIC java/lang/Boolean.valueOf (Z)Ljava/lang/Boolean;\n" +
@@ -60,7 +32,7 @@ public class ExpressionGenTest extends LightDaemonAnalyzerTestCase {
         JetProperty p = PsiTreeUtil.getParentOfType(getFile().findElementAt(0), JetProperty.class);
 
         TraceMethodVisitor trace = new TraceMethodVisitor();
-        p.getInitializer().accept(new ExpressionCodegen(trace, null, null, new FrameMap()));
+        p.getInitializer().accept(new ExpressionCodegen(trace, null, null, new FrameMap(), new JetTypeMapper(null), Type.VOID_TYPE));
 
         StringWriter out = new StringWriter();
         trace.print(new PrintWriter(out));
diff --git a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
index ccd078b485a..5c7cae20435 100644
--- a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
@@ -28,8 +28,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         final String text = generateToText();
         System.out.println(text);
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         Object[] args = new Object[] { new String[0] };
         main.invoke(null, args);
     }
@@ -39,8 +38,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         final String text = generateToText();
         System.out.println(text);
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         final Object returnValue = main.invoke(null, new Object[0]);
         assertEquals(new Integer(42), returnValue);
     }
@@ -50,8 +48,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         final String text = generateToText();
         System.out.println(text);
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         final Object returnValue = main.invoke(null, 50);
         assertEquals(new Integer(50), returnValue);
     }
@@ -61,16 +58,15 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         final String text = generateToText();
         System.out.println(text);
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         final Object returnValue = main.invoke(null, 76);
         assertEquals(new Integer(50), returnValue);
     }
 
     public void testCurrentTime() throws Exception {
         loadFile("currentTime.jet");
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        System.out.println(generateToText());
+        final Method main = generateFunction();
         final long returnValue = (Long) main.invoke(null);
         long currentTime = System.currentTimeMillis();
         assertTrue(Math.abs(returnValue - currentTime) <= 1L);
@@ -78,8 +74,8 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
 
     public void testIdentityHashCode() throws Exception {
         loadFile("identityHashCode.jet");
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        System.out.println(generateToText());
+        final Method main = generateFunction();
         Object o = new Object();
         final int returnValue = (Integer) main.invoke(null, o);
         assertEquals(returnValue, System.identityHashCode(o));
@@ -87,8 +83,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
 
     public void testSystemOut() throws Exception {
         loadFile("systemOut.jet");
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         final Object returnValue = main.invoke(null);
         assertEquals(returnValue, System.out);
     }
@@ -98,8 +93,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
 
         System.out.println(generateToText());
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);   // assert that it can be verified
+        generateFunction();  // assert that it can be verified
     }
 
     public void testPlus() throws Exception {
@@ -107,12 +101,37 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
 
         System.out.println(generateToText());
 
-        final Class aClass = generateToClass();
-        final Method main = firstMethod(aClass);
+        final Method main = generateFunction();
         final int returnValue = (Integer) main.invoke(null, 37, 5);
         assertEquals(42, returnValue);
     }
 
+    public void testIf() throws Exception {
+        loadFile("if.jet");
+
+        System.out.println(generateToText());
+        final Method main = generateFunction();
+        assertEquals(15, main.invoke(null, true));
+        assertEquals(20, main.invoke(null, false));
+    }
+
+    public void testSingleBranchIf() throws Exception {
+        loadFile("singleBranchIf.jet");
+
+        System.out.println(generateToText());
+        final Method main = generateFunction();
+        assertEquals(15, main.invoke(null, true));
+        assertEquals(20, main.invoke(null, false));
+    }
+
+    public void testAssign() throws Exception {
+        loadFile("assign.jet");
+
+        System.out.println(generateToText());
+        final Method main = generateFunction();
+        assertEquals(2, main.invoke(null));
+    }
+
     private void loadFile(final String name) {
         myFixture.configureByFile(JetParsingTest.getTestDataDir() + "/codegen/" + name);
     }
@@ -143,7 +162,8 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         return aClass;
     }
 
-    private static Method firstMethod(Class aClass) {
+    private Method generateFunction() {
+        Class aClass = generateToClass();
         return aClass.getMethods()[0];
     }