Implementing reflection in WASM

classlib/src/main/java/org/teavm/classlib/java/lang/reflect/TArray.java

@@ -17,13 +17,13 @@ package org.teavm.classlib.java.lang.reflect;
 
 import org.teavm.classlib.java.lang.*;
 import org.teavm.dependency.PluggableDependency;
+import org.teavm.interop.DelegateTo;
 import org.teavm.javascript.spi.GeneratedBy;
 import org.teavm.platform.PlatformClass;
+import org.teavm.runtime.Allocator;
+import org.teavm.runtime.RuntimeClass;
+import org.teavm.runtime.RuntimeObject;
 
-/**
- *
- * @author Alexey Andreev
- */
 public final class TArray extends TObject {
     @GeneratedBy(ArrayNativeGenerator.class)
     @PluggableDependency(ArrayNativeGenerator.class)
@@ -44,8 +44,14 @@ public final class TArray extends TObject {
 
     @GeneratedBy(ArrayNativeGenerator.class)
     @PluggableDependency(ArrayNativeGenerator.class)
+    @DelegateTo("newInstanceLowLevel")
     private static native TObject newInstanceImpl(PlatformClass componentType, int length);
 
+    @SuppressWarnings("unused")
+    private static RuntimeObject newInstanceLowLevel(RuntimeClass cls, int length) {
+        return Allocator.allocateArray(cls, length).toStructure();
+    }
+
     public static TObject get(TObject array, int index) throws TIllegalArgumentException,
             TArrayIndexOutOfBoundsException {
         if (index < 0 || index >= getLength(array)) {

core/src/main/java/org/teavm/javascript/backend/JavaScriptTarget.java

@@ -39,6 +39,7 @@ import org.teavm.codegen.SourceWriterBuilder;
 import org.teavm.debugging.information.DebugInformationEmitter;
 import org.teavm.debugging.information.SourceLocation;
 import org.teavm.dependency.DependencyChecker;
+import org.teavm.dependency.DependencyListener;
 import org.teavm.dependency.MethodDependency;
 import org.teavm.javascript.Renderer;
 import org.teavm.javascript.RenderingException;
@@ -88,6 +89,11 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
         return Collections.emptyList();
     }
 
+    @Override
+    public List<DependencyListener> getDependencyListeners() {
+        return Collections.emptyList();
+    }
+
     @Override
     public void setController(TeaVMTargetController controller) {
         this.controller = controller;

core/src/main/java/org/teavm/vm/TeaVM.java

@@ -137,6 +137,9 @@ public class TeaVM implements TeaVMHost, ServiceRepository {
         for (ClassHolderTransformer transformer : target.getTransformers()) {
             dependencyChecker.addClassTransformer(transformer);
         }
+        for (DependencyListener listener : target.getDependencyListeners()) {
+            dependencyChecker.addDependencyListener(listener);
+        }
 
         for (TeaVMHostExtension extension : target.getHostExtensions()) {
             for (Class<?> extensionType : getExtensionTypes(extension)) {

core/src/main/java/org/teavm/vm/TeaVMTarget.java

@@ -18,6 +18,7 @@ package org.teavm.vm;
 import java.io.OutputStream;
 import java.util.List;
 import org.teavm.dependency.DependencyChecker;
+import org.teavm.dependency.DependencyListener;
 import org.teavm.model.ClassHolderTransformer;
 import org.teavm.model.ListableClassHolderSource;
 import org.teavm.vm.spi.TeaVMHostExtension;
@@ -25,6 +26,8 @@ import org.teavm.vm.spi.TeaVMHostExtension;
 public interface TeaVMTarget {
     List<ClassHolderTransformer> getTransformers();
 
+    List<DependencyListener> getDependencyListeners();
+
     void setController(TeaVMTargetController controller);
 
     List<TeaVMHostExtension> getHostExtensions();

core/src/main/java/org/teavm/wasm/Example.java

@@ -71,13 +71,13 @@ public final class Example {
         WasmRuntime.print(new Object().hashCode());
         WasmRuntime.print(new Object().hashCode());
 
-        /*List<Integer> list = new ArrayList<>(Arrays.asList(333, 444, 555));
+        List<Integer> list = new ArrayList<>(Arrays.asList(333, 444, 555));
         list.add(1234);
-        list.remove(444);
+        list.remove((Integer) 444);
 
         for (int item : list) {
             WasmRuntime.print(item);
-        }*/
+        }
     }
 
     private static Base instance(int index) {

core/src/main/java/org/teavm/wasm/WasmTarget.java

@@ -15,7 +15,6 @@
  */
 package org.teavm.wasm;
 
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
@@ -29,9 +28,12 @@ import java.util.Set;
 import org.teavm.ast.decompilation.Decompiler;
 import org.teavm.dependency.ClassDependency;
 import org.teavm.dependency.DependencyChecker;
+import org.teavm.dependency.DependencyListener;
 import org.teavm.interop.Address;
+import org.teavm.interop.DelegateTo;
 import org.teavm.interop.Import;
 import org.teavm.interop.StaticInit;
+import org.teavm.model.AnnotationHolder;
 import org.teavm.model.BasicBlock;
 import org.teavm.model.CallLocation;
 import org.teavm.model.ClassHolder;
@@ -59,14 +61,13 @@ import org.teavm.runtime.RuntimeClass;
 import org.teavm.runtime.RuntimeJavaObject;
 import org.teavm.runtime.RuntimeObject;
 import org.teavm.vm.BuildTarget;
-import org.teavm.vm.TeaVM;
-import org.teavm.vm.TeaVMBuilder;
 import org.teavm.vm.TeaVMEntryPoint;
 import org.teavm.vm.TeaVMTarget;
 import org.teavm.vm.TeaVMTargetController;
 import org.teavm.vm.spi.TeaVMHostExtension;
 import org.teavm.wasm.binary.BinaryWriter;
 import org.teavm.wasm.generate.WasmClassGenerator;
+import org.teavm.wasm.generate.WasmDependencyListener;
 import org.teavm.wasm.generate.WasmGenerationContext;
 import org.teavm.wasm.generate.WasmGenerator;
 import org.teavm.wasm.generate.WasmMangling;
@@ -126,6 +127,13 @@ public class WasmTarget implements TeaVMTarget {
         return transformers;
     }
 
+    @Override
+    public List<DependencyListener> getDependencyListeners() {
+        List<DependencyListener> listeners = new ArrayList<>();
+        listeners.add(new WasmDependencyListener());
+        return listeners;
+    }
+
     @Override
     public void contributeDependencies(DependencyChecker dependencyChecker) {
         for (Class type : Arrays.asList(int.class, long.class, float.class, double.class)) {
@@ -171,8 +179,7 @@ public class WasmTarget implements TeaVMTarget {
         VirtualTableProvider vtableProvider = createVirtualTableProvider(classes);
         TagRegistry tagRegistry = new TagRegistry(classes);
         BinaryWriter binaryWriter = new BinaryWriter(256);
-        WasmClassGenerator classGenerator = new WasmClassGenerator(controller.getUnprocessedClassSource(),
+        WasmClassGenerator classGenerator = new WasmClassGenerator(classes, vtableProvider, tagRegistry, binaryWriter);
-                vtableProvider, tagRegistry, binaryWriter);
 
         Decompiler decompiler = new Decompiler(classes, controller.getClassLoader(), new HashSet<>(),
                 new HashSet<>());
@@ -205,7 +212,26 @@ public class WasmTarget implements TeaVMTarget {
                     continue;
                 }
 
-                if (method.hasModifier(ElementModifier.NATIVE)) {
+                MethodHolder implementor = method;
+                AnnotationHolder delegateAnnot = method.getAnnotations().get(DelegateTo.class.getName());
+                if (delegateAnnot != null) {
+                    String methodName = delegateAnnot.getValue("value").getString();
+                    boolean found = false;
+                    for (MethodHolder candidate : cls.getMethods()) {
+                        if (candidate.getName().equals(methodName)) {
+                            if (found) {
+                                controller.getDiagnostics().error(new CallLocation(method.getReference()),
+                                        "Method is delegated to " + methodName + " but several implementations "
+                                        + "found");
+                                break;
+                            }
+                            implementor = candidate;
+                            found = true;
+                        }
+                    }
+                }
+
+                if (implementor.hasModifier(ElementModifier.NATIVE)) {
                     if (context.getImportedMethod(method.getReference()) == null) {
                         CallLocation location = new CallLocation(method.getReference());
                         controller.getDiagnostics().error(location, "Method {{m0}} is native but "
@@ -214,10 +240,10 @@ public class WasmTarget implements TeaVMTarget {
                     module.add(generator.generateNative(method.getReference()));
                     continue;
                 }
-                if (method.getProgram() == null || method.getProgram().basicBlockCount() == 0) {
+                if (implementor.getProgram() == null || implementor.getProgram().basicBlockCount() == 0) {
                     continue;
                 }
-                module.add(generator.generate(method.getReference()));
+                module.add(generator.generate(method.getReference(), implementor));
                 if (controller.wasCancelled()) {
                     return;
                 }
@@ -365,14 +391,4 @@ public class WasmTarget implements TeaVMTarget {
 
         return new VirtualTableProvider(classes, virtualMethods);
     }
-
-    public static void main(String[] args) throws IOException {
-        TeaVM vm = new TeaVMBuilder(new WasmTarget()).build();
-        vm.installPlugins();
-        vm.entryPoint("main", new MethodReference(Example.class, "main", String[].class, void.class));
-        try (OutputStream output = new FileOutputStream(args[0])) {
-            vm.build(output, null);
-            System.err.println("Problems found: " + vm.getProblemProvider().getProblems().size());
-        }
-    }
 }

core/src/main/java/org/teavm/wasm/generate/WasmDependencyListener.java

@@ -0,0 +1,43 @@
+/*
+ *  Copyright 2016 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.wasm.generate;
+
+import org.teavm.dependency.AbstractDependencyListener;
+import org.teavm.dependency.DependencyAgent;
+import org.teavm.dependency.MethodDependency;
+import org.teavm.interop.DelegateTo;
+import org.teavm.model.AnnotationReader;
+import org.teavm.model.CallLocation;
+import org.teavm.model.ClassReader;
+import org.teavm.model.MethodReader;
+
+public class WasmDependencyListener extends AbstractDependencyListener {
+    @Override
+    public void methodReached(DependencyAgent agent, MethodDependency method, CallLocation location) {
+        AnnotationReader delegateAnnot = method.getMethod().getAnnotations().get(DelegateTo.class.getName());
+        if (delegateAnnot != null) {
+            String delegateMethodName = delegateAnnot.getValue("value").getString();
+            ClassReader cls = agent.getClassSource().get(method.getReference().getClassName());
+            for (MethodReader delegate : cls.getMethods()) {
+                if (delegate.getName().equals(delegateMethodName)) {
+                    if (delegate != method.getMethod()) {
+                        agent.linkMethod(delegate.getReference(), location).use();
+                    }
+                }
+            }
+        }
+    }
+}

core/src/main/java/org/teavm/wasm/generate/WasmGenerationVisitor.java

@@ -45,6 +45,7 @@ import org.teavm.ast.MonitorExitStatement;
 import org.teavm.ast.NewArrayExpr;
 import org.teavm.ast.NewExpr;
 import org.teavm.ast.NewMultiArrayExpr;
+import org.teavm.ast.NodeLocation;
 import org.teavm.ast.OperationType;
 import org.teavm.ast.PrimitiveCastExpr;
 import org.teavm.ast.QualificationExpr;
@@ -114,6 +115,7 @@ import org.teavm.wasm.model.expression.WasmSwitch;
 import org.teavm.wasm.model.expression.WasmUnreachable;
 
 class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
+    private static FieldReference tagField = new FieldReference(RuntimeClass.class.getName(), "tag");
     private WasmGenerationContext context;
     private WasmClassGenerator classGenerator;
     private WasmFunction function;
@@ -165,6 +167,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
                         call.getArguments().add(result);
                         expr.getSecondOperand().acceptVisitor(this);
                         call.getArguments().add(result);
+                        call.setLocation(expr.getLocation());
                         result = call;
                         break;
                 }
@@ -215,6 +218,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
                 call.getArguments().add(result);
                 expr.getSecondOperand().acceptVisitor(this);
                 call.getArguments().add(result);
+                call.setLocation(expr.getLocation());
                 result = call;
                 break;
             }
@@ -251,6 +255,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
                     break;
             }
         }
+        result.setLocation(expr.getLocation());
     }
 
     private void generateBinary(WasmIntBinaryOperation intOp, BinaryExpr expr) {
@@ -282,6 +287,8 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
             case DOUBLE:
                 throw new AssertionError("Can't translate operation " + intOp + " for type " + expr.getType());
         }
+
+        result.setLocation(expr.getLocation());
     }
 
     private Class<?> convertType(OperationType type) {
@@ -304,11 +311,15 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         expr.getFirstOperand().acceptVisitor(this);
         WasmBranch branch = new WasmBranch(negate(result), block);
         branch.setResult(new WasmInt32Constant(0));
+        branch.setLocation(expr.getLocation());
+        branch.getResult().setLocation(expr.getLocation());
         block.getBody().add(branch);
 
         expr.getSecondOperand().acceptVisitor(this);
         block.getBody().add(result);
 
+        block.setLocation(expr.getLocation());
+
         result = block;
     }
 
@@ -318,11 +329,15 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         expr.getFirstOperand().acceptVisitor(this);
         WasmBranch branch = new WasmBranch(result, block);
         branch.setResult(new WasmInt32Constant(1));
+        branch.setLocation(expr.getLocation());
+        branch.getResult().setLocation(expr.getLocation());
         block.getBody().add(branch);
 
         expr.getSecondOperand().acceptVisitor(this);
         block.getBody().add(result);
 
+        block.setLocation(expr.getLocation());
+
         result = block;
     }
 
@@ -333,22 +348,28 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
                 expr.getOperand().acceptVisitor(this);
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHL,
                         result, new WasmInt32Constant(24));
+                result.setLocation(expr.getLocation());
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHR_SIGNED,
                         result, new WasmInt32Constant(24));
+                result.setLocation(expr.getLocation());
                 break;
             case INT_TO_SHORT:
                 expr.getOperand().acceptVisitor(this);
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHL,
                         result, new WasmInt32Constant(16));
+                result.setLocation(expr.getLocation());
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHR_SIGNED,
                         result, new WasmInt32Constant(16));
+                result.setLocation(expr.getLocation());
                 break;
             case INT_TO_CHAR:
                 expr.getOperand().acceptVisitor(this);
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHL,
                         result, new WasmInt32Constant(16));
+                result.setLocation(expr.getLocation());
                 result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SHR_UNSIGNED,
                         result, new WasmInt32Constant(16));
+                result.setLocation(expr.getLocation());
                 break;
             case LENGTH:
                 expr.getOperand().acceptVisitor(this);
@@ -364,18 +385,22 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
                     case INT:
                         result = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.SUB,
                                 new WasmInt32Constant(0), result);
+                        result.setLocation(expr.getLocation());
                         break;
                     case LONG:
                         result = new WasmIntBinary(WasmIntType.INT64, WasmIntBinaryOperation.SUB,
                                 new WasmInt64Constant(0), result);
+                        result.setLocation(expr.getLocation());
                         break;
                     case FLOAT:
                         result = new WasmFloatBinary(WasmFloatType.FLOAT32, WasmFloatBinaryOperation.SUB,
                                 new WasmFloat32Constant(0), result);
+                        result.setLocation(expr.getLocation());
                         break;
                     case DOUBLE:
                         result = new WasmFloatBinary(WasmFloatType.FLOAT64, WasmFloatBinaryOperation.SUB,
                                 new WasmFloat64Constant(0), result);
+                        result.setLocation(expr.getLocation());
                         break;
                 }
                 break;
@@ -388,9 +413,13 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
     private WasmExpression generateArrayLength(WasmExpression array) {
         int sizeOffset = classGenerator.getFieldOffset(new FieldReference(RuntimeArray.class.getName(), "size"));
 
-        WasmIntBinary ptr = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD,
+        WasmExpression ptr = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD,
                 array, new WasmInt32Constant(sizeOffset));
-        return new WasmLoadInt32(4, ptr, WasmInt32Subtype.INT32);
+        ptr.setLocation(array.getLocation());
+
+        WasmExpression length = new WasmLoadInt32(4, ptr, WasmInt32Subtype.INT32);
+        length.setLocation(array.getLocation());
+        return length;
     }
 
     @Override
@@ -399,14 +428,16 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         if (left == null) {
             statement.getRightValue().acceptVisitor(this);
             result = new WasmDrop(result);
+            result.setLocation(statement.getLocation());
         } else if (left instanceof VariableExpr) {
             VariableExpr varExpr = (VariableExpr) left;
             WasmLocal local = function.getLocalVariables().get(varExpr.getIndex() - firstVariable);
             statement.getRightValue().acceptVisitor(this);
             result = new WasmSetLocal(local, result);
+            result.setLocation(statement.getLocation());
         } else if (left instanceof QualificationExpr) {
             QualificationExpr lhs = (QualificationExpr) left;
-            storeField(lhs.getQualified(), lhs.getField(), statement.getRightValue());
+            storeField(lhs.getQualified(), lhs.getField(), statement.getRightValue(), statement.getLocation());
         } else if (left instanceof SubscriptExpr) {
             SubscriptExpr lhs = (SubscriptExpr) left;
             storeArrayItem(lhs, statement.getRightValue());
@@ -415,8 +446,8 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         }
     }
 
-    private void storeField(Expr qualified, FieldReference field, Expr value) {
+    private void storeField(Expr qualified, FieldReference field, Expr value, NodeLocation location) {
-        WasmExpression address = getAddress(qualified, field);
+        WasmExpression address = getAddress(qualified, field, location);
         ValueType type = context.getFieldType(field);
         value.acceptVisitor(this);
         if (type instanceof ValueType.Primitive) {
@@ -447,6 +478,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         } else {
             result = new WasmStoreInt32(4, address, result, WasmInt32Subtype.INT32);
         }
+        result.setLocation(location);
     }
 
     private void storeArrayItem(SubscriptExpr leftValue, Expr rightValue) {
@@ -741,7 +773,8 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         } else if (expr.getType() == InvocationType.CONSTRUCTOR) {
             WasmBlock block = new WasmBlock(false);
             WasmLocal tmp = function.getLocalVariables().get(getTemporaryInt32());
-            block.getBody().add(new WasmSetLocal(tmp, allocateObject(expr.getMethod().getClassName())));
+            block.getBody().add(new WasmSetLocal(tmp, allocateObject(expr.getMethod().getClassName(),
+                    expr.getLocation())));
 
             String methodName = WasmMangling.mangleMethod(expr.getMethod());
             WasmCall call = new WasmCall(methodName);
@@ -825,7 +858,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
 
     @Override
     public void visit(QualificationExpr expr) {
-        WasmExpression address = getAddress(expr.getQualified(), expr.getField());
+        WasmExpression address = getAddress(expr.getQualified(), expr.getField(), expr.getLocation());
 
         ValueType type = context.getFieldType(expr.getField());
         if (type instanceof ValueType.Primitive) {
@@ -858,14 +891,25 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         }
     }
 
-    private WasmExpression getAddress(Expr qualified, FieldReference field) {
+    private WasmExpression getAddress(Expr qualified, FieldReference field, NodeLocation location) {
         int offset = classGenerator.getFieldOffset(field);
         if (qualified == null) {
-            return new WasmInt32Constant(offset);
+            WasmExpression result = new WasmInt32Constant(offset);
+            result.setLocation(location);
+            return result;
         } else {
             qualified.acceptVisitor(this);
-            return new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD, result,
+            if (offset != 0) {
-                    new WasmInt32Constant(offset));
+                WasmExpression offsetExpr = new WasmInt32Constant(offset);
+                offsetExpr.setLocation(qualified.getLocation());
+
+                WasmExpression address = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD,
+                        result, offsetExpr);
+                address.setLocation(location);
+                return address;
+            } else {
+                return result;
+            }
         }
     }
 
@@ -878,6 +922,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         WasmBlock wasmTarget = breakTargets.get(target);
         usedBlocks.add(wasmTarget);
         result = new WasmBreak(wasmTarget);
+        result.setLocation(statement.getLocation());
     }
 
     @Override
@@ -889,19 +934,21 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         WasmBlock wasmTarget = continueTargets.get(target);
         usedBlocks.add(wasmTarget);
         result = new WasmBreak(wasmTarget);
+        result.setLocation(statement.getLocation());
     }
 
     @Override
     public void visit(NewExpr expr) {
-        result = allocateObject(expr.getConstructedClass());
+        result = allocateObject(expr.getConstructedClass(), expr.getLocation());
     }
 
-    private WasmExpression allocateObject(String className) {
+    private WasmExpression allocateObject(String className, NodeLocation location) {
         int tag = classGenerator.getClassPointer(ValueType.object(className));
         String allocName = WasmMangling.mangleMethod(new MethodReference(Allocator.class, "allocate",
                 RuntimeClass.class, Address.class));
         WasmCall call = new WasmCall(allocName);
         call.getArguments().add(new WasmInt32Constant(tag));
+        call.setLocation(location);
         return call;
     }
 
@@ -916,6 +963,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         call.getArguments().add(new WasmInt32Constant(classPointer));
         expr.getLength().acceptVisitor(this);
         call.getArguments().add(result);
+        call.setLocation(expr.getLocation());
 
         result = call;
     }
@@ -932,6 +980,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
             result = null;
         }
         result = new WasmReturn(result);
+        result.setLocation(statement.getLocation());
     }
 
     @Override
@@ -944,9 +993,11 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
             Collections.sort(ranges, Comparator.comparingInt(range -> range.lower));
 
             WasmBlock block = new WasmBlock(false);
+            block.setLocation(expr.getLocation());
             WasmLocal tagVar = function.getLocalVariables().get(getTemporaryInt32());
+            int tagOffset = classGenerator.getFieldOffset(tagField);
             WasmExpression tagPtr = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.ADD,
-                    getReferenceToClass(result), new WasmInt32Constant(8));
+                    getReferenceToClass(result), new WasmInt32Constant(tagOffset));
             block.getBody().add(new WasmSetLocal(tagVar, new WasmLoadInt32(4, tagPtr, WasmInt32Subtype.INT32)));
 
             WasmExpression lowerThanMinCond = new WasmIntBinary(WasmIntType.INT32, WasmIntBinaryOperation.LT_SIGNED,
@@ -990,6 +1041,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
     @Override
     public void visit(ThrowStatement statement) {
         WasmBlock block = new WasmBlock(false);
+        block.setLocation(statement.getLocation());
         statement.getException().acceptVisitor(this);
         block.getBody().add(result);
 
@@ -1007,6 +1059,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
     public void visit(InitClassStatement statement) {
         if (classGenerator.hasClinit(statement.getClassName())) {
             result = new WasmCall(WasmMangling.mangleInitializer(statement.getClassName()));
+            result.setLocation(statement.getLocation());
         } else {
             result = null;
         }
@@ -1017,7 +1070,7 @@ class WasmGenerationVisitor implements StatementVisitor, ExprVisitor {
         expr.getValue().acceptVisitor(this);
         result = new WasmConversion(WasmGeneratorUtil.mapType(expr.getSource()),
                 WasmGeneratorUtil.mapType(expr.getTarget()), true, result);
-
+        result.setLocation(expr.getLocation());
     }
 
     @Override

core/src/main/java/org/teavm/wasm/generate/WasmGenerator.java

@@ -24,6 +24,7 @@ import org.teavm.model.ElementModifier;
 import org.teavm.model.FieldReference;
 import org.teavm.model.MethodHolder;
 import org.teavm.model.MethodReference;
+import org.teavm.model.Program;
 import org.teavm.model.ValueType;
 import org.teavm.runtime.RuntimeClass;
 import org.teavm.wasm.model.WasmFunction;
@@ -53,11 +54,11 @@ public class WasmGenerator {
         this.classGenerator = classGenerator;
     }
 
-    public WasmFunction generate(MethodReference methodReference) {
+    public WasmFunction generate(MethodReference methodReference, MethodHolder bodyMethod) {
         ClassHolder cls = classSource.get(methodReference.getClassName());
         MethodHolder method = cls.getMethod(methodReference.getDescriptor());
 
-        RegularMethodNode methodAst = decompiler.decompileRegular(method);
+        RegularMethodNode methodAst = decompiler.decompileRegular(bodyMethod);
         WasmFunction function = new WasmFunction(WasmMangling.mangleMethod(methodReference));
         int firstVariable = method.hasModifier(ElementModifier.STATIC) ? 1 : 0;
         for (int i = firstVariable; i < methodAst.getVariables().size(); ++i) {

core/src/main/java/org/teavm/wasm/model/expression/WasmExpression.java

@@ -15,9 +15,21 @@
  */
 package org.teavm.wasm.model.expression;
 
+import org.teavm.ast.NodeLocation;
+
 public abstract class WasmExpression {
+    private NodeLocation location;
+
     WasmExpression() {
     }
 
+    public NodeLocation getLocation() {
+        return location;
+    }
+
+    public void setLocation(NodeLocation location) {
+        this.location = location;
+    }
+
     public abstract void acceptVisitor(WasmExpressionVisitor visitor);
 }

core/src/main/java/org/teavm/wasm/render/WasmRenderingVisitor.java

@@ -97,7 +97,11 @@ class WasmRenderingVisitor implements WasmExpressionVisitor {
     }
 
     WasmRenderingVisitor line(WasmExpression expression) {
-        return lf().append(expression);
+        if (expression.getLocation() != null) {
+            lf().append(";; " + expression.getLocation().getFileName() + ":" + expression.getLocation().getLine());
+        }
+        lf().append(expression);
+        return this;
     }
 
     WasmRenderingVisitor indent() {

interop/core/src/main/java/org/teavm/interop/DelegateTo.java

@@ -0,0 +1,27 @@
+/*
+ *  Copyright 2016 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.interop;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface DelegateTo {
+    String value();
+}