simplify AST (idea like)

src/com/google/dart/compiler/backend/js/JsConstructExpressionVisitor.java

@@ -11,7 +11,6 @@ import com.google.dart.compiler.backend.js.ast.*;
  * normally be surrounded by parentheses.
  */
 public class JsConstructExpressionVisitor extends JsVisitor {
-
     public static boolean exec(JsExpression expression) {
         if (JsPrecedenceVisitor.exec(expression) < JsPrecedenceVisitor.PRECEDENCE_NEW) {
             return true;
@@ -21,7 +20,7 @@ public class JsConstructExpressionVisitor extends JsVisitor {
         return visitor.containsInvocation;
     }
 
-  private boolean containsInvocation = false;
+    private boolean containsInvocation;
 
     private JsConstructExpressionVisitor() {
     }
@@ -85,7 +84,7 @@ public class JsConstructExpressionVisitor extends JsVisitor {
      * We only look at nodes that would not normally be surrounded by parentheses.
      */
     @Override
-  public <T extends JsVisitable> T accept(T node) {
+    public <T extends JsNode> T accept(T node) {
         // Assign to Object to prevent 'inconvertible types' compile errors due
         // to http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6548436
         // reproducible in jdk1.6.0_02.

src/com/google/dart/compiler/backend/js/JsFirstExpressionVisitor.java

@@ -112,9 +112,4 @@ public class JsFirstExpressionVisitor extends JsVisitor {
     public boolean visit(JsPrefixOperation x, JsContext ctx) {
         return false;
     }
-
-    @Override
-    public boolean visit(JsRegExp x, JsContext ctx) {
-        return false;
-    }
 }

src/com/google/dart/compiler/backend/js/JsPrecedenceVisitor.java

@@ -10,22 +10,22 @@ import com.google.dart.compiler.backend.js.ast.JsVars.JsVar;
 /**
  * Precedence indices from "JavaScript - The Definitive Guide" 4th Edition (page
  * 57)
- *
+ * <p/>
  * Precedence 17 is for indivisible primaries that either don't have children,
  * or provide their own delimiters.
- *
+ * <p/>
  * Precedence 16 is for really important things that have their own AST classes.
- *
+ * <p/>
  * Precedence 15 is for the new construct.
- *
+ * <p/>
  * Precedence 14 is for unary operators.
- *
+ * <p/>
  * Precedences 12 through 4 are for non-assigning binary operators.
- *
+ * <p/>
  * Precedence 3 is for the tertiary conditional.
- *
+ * <p/>
  * Precedence 2 is for assignments.
- *
+ * <p/>
  * Precedence 1 is for comma operations.
  */
 class JsPrecedenceVisitor extends JsVisitor {
@@ -116,7 +116,7 @@ class JsPrecedenceVisitor extends JsVisitor {
     }
 
     @Override
-  public boolean visit(JsEmpty x, JsContext ctx) {
+    public void visit(JsEmpty x, JsContext ctx) {
         throw new RuntimeException("Only expressions have precedence.");
     }
 
@@ -161,7 +161,8 @@ class JsPrecedenceVisitor extends JsVisitor {
     public boolean visit(JsNameRef x, JsContext ctx) {
         if (x.isLeaf()) {
             answer = 17; // primary
-    } else {
+        }
+        else {
             answer = 16; // property access
         }
         return false;
@@ -174,21 +175,18 @@ class JsPrecedenceVisitor extends JsVisitor {
     }
 
     @Override
-  public boolean visit(JsNullLiteral x, JsContext ctx) {
+    public void visit(JsNullLiteral x, JsContext ctx) {
         answer = 17; // primary
-    return false;
     }
 
     @Override
-    public boolean visit(JsNumberLiteral.JsIntLiteral x, JsContext ctx) {
+    public void visit(JsNumberLiteral.JsIntLiteral x, JsContext ctx) {
         answer = 17; // primary
-        return false;
     }
 
     @Override
-    public boolean visit(JsNumberLiteral.JsDoubleLiteral x, JsContext ctx) {
+    public void visit(JsNumberLiteral.JsDoubleLiteral x, JsContext ctx) {
         answer = 17; // primary
-        return false;
     }
 
     @Override
@@ -226,9 +224,8 @@ class JsPrecedenceVisitor extends JsVisitor {
     }
 
     @Override
-  public boolean visit(JsRegExp x, JsContext ctx) {
+    public void visit(JsRegExp x, JsContext ctx) {
         answer = 17; // primary
-    return false;
     }
 
     @Override
@@ -237,9 +234,8 @@ class JsPrecedenceVisitor extends JsVisitor {
     }
 
     @Override
-  public boolean visit(JsStringLiteral x, JsContext ctx) {
+    public void visit(JsStringLiteral x, JsContext ctx) {
         answer = 17; // primary
-    return false;
     }
 
     @Override

src/com/google/dart/compiler/backend/js/JsRequiresSemiVisitor.java

@@ -55,11 +55,6 @@ public class JsRequiresSemiVisitor extends JsVisitor {
     return false;
   }
 
-  @Override
-  public boolean visit(JsEmpty x, JsContext ctx) {
-    return false;
-  }
-
   @Override
   public boolean visit(JsExpressionStatement x, JsContext ctx) {
     return false;

src/com/google/dart/compiler/backend/js/JsToStringGenerationVisitor.java

@@ -323,7 +323,7 @@ public class JsToStringGenerationVisitor extends JsVisitor {
     public boolean visit(JsCase x, JsContext ctx) {
         p.print(CHARS_CASE);
         space();
-        accept(x.getCaseExpr());
+        accept(x.getCaseExpression());
         _colon();
         newlineOpt();
 
@@ -450,8 +450,7 @@ public class JsToStringGenerationVisitor extends JsVisitor {
     }
 
     @Override
-    public boolean visit(JsEmpty x, JsContext ctx) {
+    public void visit(JsEmpty x, JsContext ctx) {
-        return false;
     }
 
     @Override
@@ -650,12 +649,12 @@ public class JsToStringGenerationVisitor extends JsVisitor {
         p.print(CHARS_NEW);
         space();
 
-        JsExpression ctorExpr = x.getConstructorExpression();
+        JsExpression constructorExpression = x.getConstructorExpression();
-        boolean needsParens = JsConstructExpressionVisitor.exec(ctorExpr);
+        boolean needsParens = JsConstructExpressionVisitor.exec(constructorExpression);
         if (needsParens) {
             leftParen();
         }
-        accept(ctorExpr);
+        accept(constructorExpression);
         if (needsParens) {
             rightParen();
         }
@@ -668,21 +667,18 @@ public class JsToStringGenerationVisitor extends JsVisitor {
     }
 
     @Override
-    public boolean visit(JsNullLiteral x, JsContext ctx) {
+    public void visit(JsNullLiteral x, JsContext ctx) {
         p.print(CHARS_NULL);
-        return false;
     }
 
     @Override
-    public boolean visit(JsIntLiteral x, JsContext ctx) {
+    public void visit(JsIntLiteral x, JsContext ctx) {
         p.print(x.value);
-        return false;
     }
 
     @Override
-    public boolean visit(JsDoubleLiteral x, JsContext ctx) {
+    public void visit(JsDoubleLiteral x, JsContext ctx) {
         p.print(x.value);
-        return false;
     }
 
     @Override
@@ -788,7 +784,7 @@ public class JsToStringGenerationVisitor extends JsVisitor {
     }
 
     @Override
-    public boolean visit(JsRegExp x, JsContext ctx) {
+    public void visit(JsRegExp x, JsContext ctx) {
         _slash();
         p.print(x.getPattern());
         _slash();
@@ -796,13 +792,12 @@ public class JsToStringGenerationVisitor extends JsVisitor {
         if (flags != null) {
             p.print(flags);
         }
-        return false;
     }
 
     @Override
     public boolean visit(JsReturn x, JsContext ctx) {
         p.print(CHARS_RETURN);
-        JsExpression expr = x.getExpr();
+        JsExpression expr = x.getExpression();
         if (expr != null) {
             space();
             accept(expr);
@@ -811,9 +806,8 @@ public class JsToStringGenerationVisitor extends JsVisitor {
     }
 
     @Override
-    public boolean visit(JsStringLiteral x, JsContext ctx) {
+    public void visit(JsStringLiteral x, JsContext ctx) {
         p.print(javaScriptString(x.getValue()));
-        return false;
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/ChameleonJsExpression.java

@@ -1,7 +1,5 @@
 package com.google.dart.compiler.backend.js.ast;
 
-import com.google.dart.compiler.common.SourceInfo;
-
 public class ChameleonJsExpression implements JsExpression {
     private JsExpression expression;
 
@@ -47,8 +45,13 @@ public class ChameleonJsExpression implements JsExpression {
     }
 
     @Override
-    public void traverse(JsVisitor visitor, JsContext context) {
+    public void accept(JsVisitor visitor, JsContext context) {
-        expression.traverse(visitor, context);
+        expression.accept(visitor, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        expression.acceptChildren(visitor, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/HasArguments.java

@@ -10,6 +10,5 @@ import java.util.List;
  * Implemented by JavaScript objects that accept arguments.
  */
 public interface HasArguments extends JsExpression {
-
   List<JsExpression> getArguments();
 }

src/com/google/dart/compiler/backend/js/ast/JsArrayAccess.java

@@ -52,12 +52,14 @@ public final class JsArrayAccess extends JsExpressionImpl {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      arrayExpression = v.accept(arrayExpression);
-      indexExpression = v.accept(indexExpression);
     }
-    v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        arrayExpression = visitor.accept(arrayExpression);
+        indexExpression = visitor.accept(indexExpression);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsArrayLiteral.java

@@ -57,11 +57,13 @@ public final class JsArrayLiteral extends JsLiteral {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            v.acceptWithInsertRemove(expressions);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(expressions);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsBinaryOperation.java

@@ -57,40 +57,31 @@ public final class JsBinaryOperation extends JsExpressionImpl {
         }
         // AND and OR can return nulls
         if (op.isAssignment()) {
-      if (op == JsBinaryOperator.ASG) {
+            return op != JsBinaryOperator.ASG || arg2.isDefinitelyNotNull();
-        return arg2.isDefinitelyNotNull();
-      } else {
-        // All other ASG's are math ops.
-        return true;
-      }
         }
 
-    if (op == JsBinaryOperator.COMMA) {
+        return op == JsBinaryOperator.COMMA && arg2.isDefinitelyNotNull();
-      return arg2.isDefinitelyNotNull();
-    }
-
-    return false;
     }
 
     @Override
     public boolean isDefinitelyNull() {
-    if (op == JsBinaryOperator.AND) {
+        return op == JsBinaryOperator.AND && arg1.isDefinitelyNull();
-      return arg1.isDefinitelyNull();
-    }
-    return false;
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         if (op.isAssignment()) {
-        arg1 = v.acceptLvalue(arg1);
+            arg1 = visitor.acceptLvalue(arg1);
-      } else {
-        arg1 = v.accept(arg1);
         }
-      arg2 = v.accept(arg2);
+        else {
+            arg1 = visitor.accept(arg1);
         }
-    v.endVisit(this, context);
+        arg2 = visitor.accept(arg2);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsBlock.java

@@ -44,11 +44,13 @@ public class JsBlock extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            v.acceptWithInsertRemove(statements);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(statements);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsBreak.java

@@ -22,8 +22,7 @@ public final class JsBreak extends JsContinue {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-        v.endVisit(this, context);
     }
 }

src/com/google/dart/compiler/backend/js/ast/JsCase.java

@@ -8,28 +8,29 @@ package com.google.dart.compiler.backend.js.ast;
  * Represents the JavaScript case statement.
  */
 public final class JsCase extends JsSwitchMember {
-
+    private JsExpression caseExpression;
-  private JsExpression caseExpr;
 
     public JsCase() {
         super();
     }
 
-  public JsExpression getCaseExpr() {
+    public JsExpression getCaseExpression() {
-    return caseExpr;
+        return caseExpression;
     }
 
-  public void setCaseExpr(JsExpression caseExpr) {
+    public void setCaseExpression(JsExpression caseExpression) {
-    this.caseExpr = caseExpr;
+        this.caseExpression = caseExpression;
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      caseExpr = v.accept(caseExpr);
-      v.acceptWithInsertRemove(statements);
     }
-    v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        caseExpression = visitor.accept(caseExpression);
+        super.acceptChildren(visitor, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsCatch.java

@@ -48,15 +48,17 @@ public class JsCatch extends JsNodeImpl implements HasCondition {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      param = v.accept(param);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        param = visitor.accept(param);
         if (condition != null) {
-        condition = v.accept(condition);
+            condition = visitor.accept(condition);
         }
-      body = v.accept(body);
+        body = visitor.accept(body);
-    }
-    v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsConditional.java

@@ -61,13 +61,15 @@ public final class JsConditional extends JsExpressionImpl {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            testExpr = v.accept(testExpr);
-            thenExpr = v.accept(thenExpr);
-            elseExpr = v.accept(elseExpr);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        testExpr = visitor.accept(testExpr);
+        thenExpr = visitor.accept(thenExpr);
+        elseExpr = visitor.accept(elseExpr);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsContext.java

@@ -14,13 +14,13 @@ public interface JsContext {
 
   boolean canRemove();
 
-  void insertAfter(JsVisitable node);
+  void insertAfter(JsNode node);
 
-  void insertBefore(JsVisitable node);
+  void insertBefore(JsNode node);
 
   boolean isLvalue();
 
   void removeMe();
 
-  void replaceMe(JsVisitable node);
+  void replaceMe(JsNode node);
 }

src/com/google/dart/compiler/backend/js/ast/JsContinue.java

@@ -6,9 +6,6 @@ package com.google.dart.compiler.backend.js.ast;
 
 import org.jetbrains.annotations.Nullable;
 
-/**
- * Represents the JavaScript continue statement.
- */
 public class JsContinue extends JsNodeImpl implements JsStatement {
     protected final String label;
 
@@ -26,9 +23,13 @@ public class JsContinue extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-        v.endVisit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsDebugger.java

@@ -13,9 +13,13 @@ public class JsDebugger extends JsNodeImpl implements JsStatement {
   }
 
   @Override
-  public void traverse(JsVisitor v, JsContext context) {
+  public void accept(JsVisitor v, JsContext context) {
     v.visit(this, context);
-    v.endVisit(this, context);
+  }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsDefault.java

@@ -8,17 +8,9 @@ package com.google.dart.compiler.backend.js.ast;
  * Represents the default option in a JavaScript swtich statement.
  */
 public final class JsDefault extends JsSwitchMember {
-
-  public JsDefault() {
-    super();
-  }
-
   @Override
-  public void traverse(JsVisitor v, JsContext context) {
+  public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+    v.visit(this, context);
-      v.acceptWithInsertRemove(statements);
-    }
-    v.endVisit(this, context);
   }
 
   @Override

src/com/google/dart/compiler/backend/js/ast/JsDoWhile.java

@@ -21,11 +21,10 @@ public class JsDoWhile extends JsWhile {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         if (v.visit(this, context)) {
             condition = v.accept(condition);
             body = v.accept(body);
         }
-        v.endVisit(this, context);
     }
 }

src/com/google/dart/compiler/backend/js/ast/JsDocComment.java

@@ -28,10 +28,15 @@ public class JsDocComment extends JsExpressionImpl {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
     }
 
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+
+    }
+
     @Override
     public boolean hasSideEffects() {
         return false;

src/com/google/dart/compiler/backend/js/ast/JsEmpty.java

@@ -4,18 +4,17 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
-/**
- * Represents an empty statement in JavaScript.
- */
 public class JsEmpty extends JsNodeImpl implements JsStatement {
-  // Interned by JsProgram
     JsEmpty() {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-    v.endVisit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsExpression.java

@@ -2,7 +2,7 @@ package com.google.dart.compiler.backend.js.ast;
 
 import com.google.dart.compiler.common.HasSourceInfo;
 
-public interface JsExpression extends JsNode, HasSourceInfo, JsVisitable {
+public interface JsExpression extends JsNode, HasSourceInfo {
     /**
      * Determines whether the expression can cause side effects.
      */

src/com/google/dart/compiler/backend/js/ast/JsExpressionImpl.java

@@ -4,6 +4,8 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
+import java.util.List;
+
 abstract class JsExpressionImpl extends JsNodeImpl implements JsExpression {
     protected JsExpressionImpl() {
     }
@@ -24,4 +26,17 @@ abstract class JsExpressionImpl extends JsNodeImpl implements JsExpression {
     public JsStatement makeStmt() {
         return new JsExpressionStatement(this);
     }
+
+    protected abstract static class JsExpressionHasArguments extends JsExpressionImpl implements HasArguments {
+        protected final List<JsExpression> arguments;
+
+        public JsExpressionHasArguments(List<JsExpression> arguments) {
+            this.arguments = arguments;
+        }
+
+        @Override
+        public List<JsExpression> getArguments() {
+            return arguments;
+        }
+    }
 }

src/com/google/dart/compiler/backend/js/ast/JsExpressionStatement.java

@@ -16,11 +16,13 @@ public final class JsExpressionStatement extends AbstractNode implements JsState
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            expression = v.accept(expression);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        expression = visitor.accept(expression);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsFor.java

@@ -71,27 +71,29 @@ public class JsFor extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         assert (!(initExpression != null && initVars != null));
 
         if (initExpression != null) {
-                initExpression = v.accept(initExpression);
+            initExpression = visitor.accept(initExpression);
         }
         else if (initVars != null) {
-                initVars = v.accept(initVars);
+            initVars = visitor.accept(initVars);
         }
 
         if (condition != null) {
-                condition = v.accept(condition);
+            condition = visitor.accept(condition);
         }
 
         if (incrementExpression != null) {
-                incrementExpression = v.accept(incrementExpression);
+            incrementExpression = visitor.accept(incrementExpression);
         }
-            body = v.accept(body);
+        body = visitor.accept(body);
-        }
-        v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsForIn.java

@@ -8,7 +8,6 @@ package com.google.dart.compiler.backend.js.ast;
  * Represents a JavaScript for..in statement.
  */
 public class JsForIn extends JsNodeImpl implements JsStatement {
-
     private JsStatement body;
     private JsExpression iterExpr;
     private JsExpression objExpr;
@@ -53,15 +52,19 @@ public class JsForIn extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         if (v.visit(this, context)) {
+
+        }
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         if (iterExpr != null) {
-        iterExpr = v.acceptLvalue(iterExpr);
+            iterExpr = visitor.acceptLvalue(iterExpr);
         }
-      objExpr = v.accept(objExpr);
+        objExpr = visitor.accept(objExpr);
-      body = v.accept(body);
+        body = visitor.accept(body);
-    }
-    v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsFunction.java

@@ -90,12 +90,14 @@ public final class JsFunction extends JsLiteral implements HasName {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            v.acceptWithInsertRemove(params);
-            body = v.accept(body);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(params);
+                    body = visitor.accept(body);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsIf.java

@@ -51,16 +51,18 @@ public final class JsIf extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            ifExpression = v.accept(ifExpression);
+    }
-            thenStatement = v.accept(thenStatement);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        ifExpression = visitor.accept(ifExpression);
+                    thenStatement = visitor.accept(thenStatement);
                     if (elseStatement != null) {
-                elseStatement = v.accept(elseStatement);
+                        elseStatement = visitor.accept(elseStatement);
                     }
     }
-        v.endVisit(this, context);
-    }
 
     @Override
     public NodeKind getKind() {

src/com/google/dart/compiler/backend/js/ast/JsInvocation.java

@@ -13,17 +13,16 @@ import java.util.List;
 /**
  * Represents a JavaScript invocation.
  */
-public final class JsInvocation extends JsExpressionImpl implements HasArguments {
+public final class JsInvocation extends JsExpressionImpl.JsExpressionHasArguments {
-    private final List<JsExpression> arguments;
     private JsExpression qualifier;
 
     public JsInvocation() {
-        arguments = new SmartList<JsExpression>();
+        super(new SmartList<JsExpression>());
     }
 
     public JsInvocation(JsExpression qualifier, List<JsExpression> arguments) {
+        super(arguments);
         this.qualifier = qualifier;
-        this.arguments = arguments;
     }
 
     public JsInvocation(JsExpression qualifier, JsExpression arg) {
@@ -68,12 +67,14 @@ public final class JsInvocation extends JsExpressionImpl implements HasArguments
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            qualifier = v.accept(qualifier);
-            v.acceptList(arguments);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        qualifier = visitor.accept(qualifier);
+        visitor.acceptList(arguments);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsLabel.java

@@ -42,11 +42,13 @@ public class JsLabel extends JsNodeImpl implements JsStatement, HasName {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            statement = v.accept(statement);
     }
-        v.endVisit(this, context);
+    
+    @Override
+        public void acceptChildren(JsVisitor visitor, JsContext context) {
+        statement = visitor.accept(statement);
         }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsLiteral.java

@@ -43,9 +43,8 @@ public abstract class JsLiteral extends JsExpressionImpl implements CanBooleanEv
         }
 
         @Override
-        public void traverse(JsVisitor v, JsContext context) {
+        public void accept(JsVisitor v, JsContext context) {
             v.visit(this, context);
-            v.endVisit(this, context);
         }
 
         @Override
@@ -87,9 +86,8 @@ public abstract class JsLiteral extends JsExpressionImpl implements CanBooleanEv
       }
 
       @Override
-      public void traverse(JsVisitor v, JsContext context) {
+      public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-        v.endVisit(this, context);
       }
 
       @Override
@@ -97,4 +95,26 @@ public abstract class JsLiteral extends JsExpressionImpl implements CanBooleanEv
         return NodeKind.BOOLEAN;
       }
     }
+
+    /**
+     * A JavaScript string literal expression.
+     */
+    public abstract static class JsValueLiteral extends JsLiteral {
+        protected JsValueLiteral() {
+        }
+
+        @Override
+        public final boolean hasSideEffects() {
+            return false;
+        }
+
+        @Override
+        public final boolean isLeaf() {
+            return true;
+        }
+
+        @Override
+        public void acceptChildren(JsVisitor visitor, JsContext context) {
+        }
+    }
 }

src/com/google/dart/compiler/backend/js/ast/JsNameRef.java

@@ -56,14 +56,7 @@ public final class JsNameRef extends JsExpressionImpl implements CanBooleanEval,
 
     @Override
     public boolean hasSideEffects() {
-        if (qualifier == null) {
+        return qualifier != null && (!qualifier.isDefinitelyNotNull() || qualifier.hasSideEffects());
-            return false;
-        }
-        if (!qualifier.isDefinitelyNotNull()) {
-            // Could trigger NPE.
-            return true;
-        }
-        return qualifier.hasSideEffects();
     }
 
     @Override
@@ -83,25 +76,17 @@ public final class JsNameRef extends JsExpressionImpl implements CanBooleanEval,
 
     @Override
     public boolean isDefinitelyNull() {
-        if (name != null) {
+        return name != null && (JsLiteral.UNDEFINED.getName() == name);
-            return (JsLiteral.UNDEFINED.getName() == name);
-        }
-        return false;
     }
 
     @Override
     public boolean isLeaf() {
-        if (qualifier == null) {
+        return qualifier == null;
-            return true;
-        }
-        else {
-            return false;
-        }
     }
 
     public void resolve(JsName name) {
         this.name = name;
-        this.ident = null;
+        ident = null;
     }
 
     public void setQualifier(JsExpression qualifier) {
@@ -109,14 +94,16 @@ public final class JsNameRef extends JsExpressionImpl implements CanBooleanEval,
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         if (qualifier != null) {
-                qualifier = v.accept(qualifier);
+                        qualifier = visitor.accept(qualifier);
                     }
     }
-        v.endVisit(this, context);
-    }
 
     @Override
     public NodeKind getKind() {

src/com/google/dart/compiler/backend/js/ast/JsNew.java

@@ -8,29 +8,20 @@ import com.intellij.util.SmartList;
 
 import java.util.List;
 
-/**
+public final class JsNew extends JsExpressionImpl.JsExpressionHasArguments {
- * Represents the JavaScript new expression.
+    private JsExpression constructorExpression;
- */
-public final class JsNew extends JsExpressionImpl implements HasArguments {
-    private final List<JsExpression> arguments;
-    private JsExpression ctorExpression;
 
-    public JsNew(JsExpression ctorExpression) {
+    public JsNew(JsExpression constructorExpression) {
-        this(ctorExpression, new SmartList<JsExpression>());
+        this(constructorExpression, new SmartList<JsExpression>());
     }
 
-    public JsNew(JsExpression ctorExpression, List<JsExpression> arguments) {
+    public JsNew(JsExpression constructorExpression, List<JsExpression> arguments) {
-        this.ctorExpression = ctorExpression;
+        super(arguments);
-        this.arguments = arguments;
+        this.constructorExpression = constructorExpression;
-    }
-
-    @Override
-    public List<JsExpression> getArguments() {
-        return arguments;
     }
 
     public JsExpression getConstructorExpression() {
-        return ctorExpression;
+        return constructorExpression;
     }
 
     @Override
@@ -51,12 +42,14 @@ public final class JsNew extends JsExpressionImpl implements HasArguments {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            ctorExpression = v.accept(ctorExpression);
-            v.acceptList(arguments);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        constructorExpression = visitor.accept(constructorExpression);
+        visitor.acceptList(arguments);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsNode.java

@@ -4,6 +4,16 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
-public interface JsNode extends JsVisitable {
+public interface JsNode {
     NodeKind getKind();
+
+    /**
+     * Causes this object to have the visitor visit itself and its children.
+     *
+     * @param visitor the visitor that should traverse this node
+     * @param context the context of an existing traversal
+     */
+    void accept(JsVisitor visitor, JsContext context);
+
+    void acceptChildren(JsVisitor visitor, JsContext context);
 }

src/com/google/dart/compiler/backend/js/ast/JsNodeImpl.java

@@ -1,7 +1,5 @@
 package com.google.dart.compiler.backend.js.ast;
 
-import com.google.dart.compiler.common.SourceInfo;
-
 abstract class JsNodeImpl extends AbstractNode {
     private Object sourceInfo;
 

src/com/google/dart/compiler/backend/js/ast/JsNullLiteral.java

@@ -4,7 +4,7 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
-public final class JsNullLiteral extends JsValueLiteral {
+public final class JsNullLiteral extends JsLiteral.JsValueLiteral {
     JsNullLiteral() {
     }
 
@@ -29,9 +29,8 @@ public final class JsNullLiteral extends JsValueLiteral {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-        v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsNumberLiteral.java

@@ -4,7 +4,7 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
-public abstract class JsNumberLiteral extends JsValueLiteral {
+public abstract class JsNumberLiteral extends JsLiteral.JsValueLiteral {
     @Override
     public boolean isDefinitelyNotNull() {
         return true;
@@ -38,9 +38,8 @@ public abstract class JsNumberLiteral extends JsValueLiteral {
         }
 
         @Override
-        public void traverse(JsVisitor v, JsContext context) {
+        public void accept(JsVisitor v, JsContext context) {
             v.visit(this, context);
-            v.endVisit(this, context);
         }
 
         public String toString() {
@@ -66,9 +65,8 @@ public abstract class JsNumberLiteral extends JsValueLiteral {
         }
 
         @Override
-        public void traverse(JsVisitor v, JsContext context) {
+        public void accept(JsVisitor v, JsContext context) {
             v.visit(this, context);
-            v.endVisit(this, context);
         }
 
         public String toString() {

src/com/google/dart/compiler/backend/js/ast/JsObjectLiteral.java

@@ -69,11 +69,13 @@ public final class JsObjectLiteral extends JsLiteral {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            v.acceptWithInsertRemove(properties);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(properties);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsParameter.java

@@ -27,9 +27,13 @@ public final class JsParameter extends JsNodeImpl implements HasName {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-    v.endVisit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsPostfixOperation.java

@@ -28,11 +28,8 @@ public final class JsPostfixOperation extends JsUnaryOperation {
   }
 
   @Override
-  public void traverse(JsVisitor v, JsContext context) {
+  public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+    v.visit(this, context);
-      super.traverse(v, context);
-    }
-    v.endVisit(this, context);
   }
 
   @Override

src/com/google/dart/compiler/backend/js/ast/JsPrefixOperation.java

@@ -4,9 +4,6 @@
 
 package com.google.dart.compiler.backend.js.ast;
 
-/**
- * A JavaScript prefix operation.
- */
 public final class JsPrefixOperation extends JsUnaryOperation implements CanBooleanEval {
 
   public JsPrefixOperation(JsUnaryOperator op) {
@@ -35,18 +32,12 @@ public final class JsPrefixOperation extends JsUnaryOperation implements CanBool
       CanBooleanEval eval = (CanBooleanEval) getArg();
       return eval.isBooleanFalse();
     }
-    if (getOperator() == JsUnaryOperator.TYPEOF) {
+      return getOperator() == JsUnaryOperator.TYPEOF;
-      return true;
-    }
-    return false;
   }
 
   @Override
   public boolean isDefinitelyNotNull() {
-    if (getOperator() == JsUnaryOperator.TYPEOF) {
+      return getOperator() == JsUnaryOperator.TYPEOF || getOperator() != JsUnaryOperator.VOID;
-      return true;
-    }
-    return getOperator() != JsUnaryOperator.VOID;
   }
 
   @Override
@@ -55,11 +46,8 @@ public final class JsPrefixOperation extends JsUnaryOperation implements CanBool
   }
 
   @Override
-  public void traverse(JsVisitor v, JsContext context) {
+  public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+    v.visit(this, context);
-      super.traverse(v, context);
-    }
-    v.endVisit(this, context);
   }
 
   @Override

src/com/google/dart/compiler/backend/js/ast/JsProgram.java

@@ -18,7 +18,7 @@ import static com.google.dart.compiler.backend.js.ast.JsNumberLiteral.JsIntLiter
  * A JavaScript program.
  */
 public final class JsProgram extends JsNodeImpl {
-    private final JsEmpty emptyStmt;
+    private final JsEmpty emptyStatement;
 
     private JsProgramFragment[] fragments;
 
@@ -29,19 +29,16 @@ public final class JsProgram extends JsNodeImpl {
     private final Map<String, JsStringLiteral> stringLiteralMap = new THashMap<String, JsStringLiteral>();
     private final JsScope topScope;
 
-    /**
-     * Constructs a JavaScript program object.
-     */
     public JsProgram(String unitId) {
         rootScope = new JsRootScope(this);
         topScope = new JsScope(rootScope, "Global", unitId);
         setFragmentCount(1);
 
-        emptyStmt = new JsEmpty();
+        emptyStatement = new JsEmpty();
     }
 
-    public JsEmpty getEmptyStmt() {
+    public JsEmpty getEmptyStatement() {
-        return emptyStmt;
+        return emptyStatement;
     }
 
     public JsBlock getFragmentBlock(int fragment) {
@@ -112,14 +109,16 @@ public final class JsProgram extends JsNodeImpl {
     }
 
     @Override
-    public void traverse(JsVisitor v, @Nullable JsContext context) {
+    public void accept(JsVisitor v, @Nullable JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
+    }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         for (JsProgramFragment fragment : fragments) {
-                v.accept(fragment);
+            visitor.accept(fragment);
         }
     }
-        v.endVisit(this, context);
-    }
 
     @Override
     public NodeKind getKind() {

src/com/google/dart/compiler/backend/js/ast/JsProgramFragment.java

@@ -8,11 +8,10 @@ package com.google.dart.compiler.backend.js.ast;
  * One independently loadable fragment of a {@link JsProgram}.
  */
 public class JsProgramFragment extends JsNodeImpl {
-
     private final JsGlobalBlock globalBlock;
 
     public JsProgramFragment() {
-    this.globalBlock = new JsGlobalBlock();
+        globalBlock = new JsGlobalBlock();
     }
 
     public JsBlock getGlobalBlock() {
@@ -20,11 +19,13 @@ public class JsProgramFragment extends JsNodeImpl {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      v.accept(globalBlock);
     }
-    v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.accept(globalBlock);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsPropertyInitializer.java

@@ -39,12 +39,14 @@ public class JsPropertyInitializer extends JsNodeImpl {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            labelExpr = v.accept(labelExpr);
-            valueExpr = v.accept(valueExpr);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        labelExpr = visitor.accept(labelExpr);
+                    valueExpr = visitor.accept(valueExpr);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsRegExp.java

@@ -7,8 +7,7 @@ package com.google.dart.compiler.backend.js.ast;
 /**
  * A JavaScript regular expression.
  */
-public final class JsRegExp extends JsValueLiteral {
+public final class JsRegExp extends JsLiteral.JsValueLiteral {
-
     private String flags;
     private String pattern;
 
@@ -44,17 +43,16 @@ public final class JsRegExp extends JsValueLiteral {
     }
 
     public void setFlags(String suffix) {
-    this.flags = suffix;
+        flags = suffix;
     }
 
     public void setPattern(String re) {
-    this.pattern = re;
+        pattern = re;
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
         v.visit(this, context);
-    v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsReturn.java

@@ -8,32 +8,33 @@ package com.google.dart.compiler.backend.js.ast;
  * A JavaScript return statement.
  */
 public final class JsReturn extends JsNodeImpl implements JsStatement {
-
+    private JsExpression expression;
-  private JsExpression expr;
 
     public JsReturn() {
     }
 
-  public JsReturn(JsExpression expr) {
+    public JsReturn(JsExpression expression) {
-    this.expr = expr;
+        this.expression = expression;
     }
 
-  public JsExpression getExpr() {
+    public JsExpression getExpression() {
-    return expr;
+        return expression;
     }
 
-  public void setExpr(JsExpression expr) {
+    public void setExpression(JsExpression expression) {
-    this.expr = expr;
+        this.expression = expression;
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      if (expr != null) {
-        expr = v.accept(expr);
     }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        if (expression != null) {
+                        expression = visitor.accept(expression);
                     }
-    v.endVisit(this, context);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsScope.java

@@ -67,8 +67,8 @@ public class JsScope {
 
     protected JsScope(@Nullable String description) {
         this.description = description;
-        this.parent = null;
+        parent = null;
-        this.scopeId = null;
+        scopeId = null;
     }
 
     /**

src/com/google/dart/compiler/backend/js/ast/JsStringLiteral.java

@@ -7,7 +7,7 @@ package com.google.dart.compiler.backend.js.ast;
 /**
  * A JavaScript string literal expression.
  */
-public final class JsStringLiteral extends JsValueLiteral {
+public final class JsStringLiteral extends JsLiteral.JsValueLiteral {
 
   private final String value;
 
@@ -41,9 +41,8 @@ public final class JsStringLiteral extends JsValueLiteral {
   }
 
   @Override
-  public void traverse(JsVisitor v, JsContext context) {
+  public void accept(JsVisitor v, JsContext context) {
     v.visit(this, context);
-    v.endVisit(this, context);
   }
 
   @Override

src/com/google/dart/compiler/backend/js/ast/JsSwitch.java

@@ -32,12 +32,14 @@ public class JsSwitch extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-    if (v.visit(this, context)) {
+        v.visit(this, context);
-      expr = v.accept(expr);
-      v.acceptWithInsertRemove(cases);
     }
-    v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        expr = visitor.accept(expr);
+        visitor.acceptWithInsertRemove(cases);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsSwitchMember.java

@@ -21,4 +21,9 @@ public abstract class JsSwitchMember extends JsNodeImpl {
     public List<JsStatement> getStatements() {
         return statements;
     }
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(statements);
+    }
 }

src/com/google/dart/compiler/backend/js/ast/JsThrow.java

@@ -23,11 +23,13 @@ public class JsThrow extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            expression = v.accept(expression);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.accept(expression);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsTry.java

@@ -40,7 +40,7 @@ public class JsTry extends JsNodeImpl implements JsStatement {
     }
 
     public void setFinallyBlock(JsBlock block) {
-        this.finallyBlock = block;
+        finallyBlock = block;
     }
 
     public void setTryBlock(JsBlock block) {
@@ -48,16 +48,18 @@ public class JsTry extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            tryBlock = v.accept(tryBlock);
+    }
-            v.acceptWithInsertRemove(catches);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        tryBlock = visitor.accept(tryBlock);
+        visitor.acceptWithInsertRemove(catches);
         if (finallyBlock != null) {
-                finallyBlock = v.accept(finallyBlock);
+            finallyBlock = visitor.accept(finallyBlock);
         }
     }
-        v.endVisit(this, context);
-    }
 
     @Override
     public NodeKind getKind() {

src/com/google/dart/compiler/backend/js/ast/JsUnaryOperation.java

@@ -41,13 +41,14 @@ public abstract class JsUnaryOperation extends JsExpressionImpl {
     }
 
     @Override
-  public void traverse(JsVisitor v, JsContext context) {
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
         if (op.isModifying()) {
             // The delete operator is practically like an assignment of undefined, so
             // for practical purposes we're treating it as an lvalue.
-      arg = v.acceptLvalue(arg);
+            arg = visitor.acceptLvalue(arg);
-    } else {
+        }
-      arg = v.accept(arg);
+        else {
+            arg = visitor.accept(arg);
         }
     }
 }

src/com/google/dart/compiler/backend/js/ast/JsValueLiteral.java

@@ -1,23 +0,0 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-package com.google.dart.compiler.backend.js.ast;
-
-/**
- * A JavaScript string literal expression.
- */
-public abstract class JsValueLiteral extends JsLiteral {
-    protected JsValueLiteral() {
-    }
-
-    @Override
-    public final boolean hasSideEffects() {
-        return false;
-    }
-
-    @Override
-    public final boolean isLeaf() {
-        return true;
-    }
-}

src/com/google/dart/compiler/backend/js/ast/JsVars.java

@@ -81,14 +81,16 @@ public class JsVars extends JsNodeImpl implements JsStatement, Iterable<JsVars.J
         }
 
         @Override
-        public void traverse(JsVisitor v, JsContext context) {
+        public void accept(JsVisitor v, JsContext context) {
-            if (v.visit(this, context)) {
+            v.visit(this, context);
+        }
+
+        @Override
+        public void acceptChildren(JsVisitor visitor, JsContext context) {
             if (initExpression != null) {
-                    initExpression = v.accept(initExpression);
+                initExpression = visitor.accept(initExpression);
             }
         }
-            v.endVisit(this, context);
-        }
 
         @Override
         public NodeKind getKind() {
@@ -116,11 +118,13 @@ public class JsVars extends JsNodeImpl implements JsStatement, Iterable<JsVars.J
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            v.acceptWithInsertRemove(vars);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        visitor.acceptWithInsertRemove(vars);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/JsVisitable.java

@@ -1,17 +0,0 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-package com.google.dart.compiler.backend.js.ast;
-
-import com.google.dart.compiler.common.HasSourceInfo;
-
-public interface JsVisitable extends HasSourceInfo {
-  /**
-   * Causes this object to have the visitor visit itself and its children.
-   * 
-   * @param visitor the visitor that should traverse this node
-   * @param context the context of an existing traversal
-   */
-  void traverse(JsVisitor visitor, JsContext context);
-}

src/com/google/dart/compiler/backend/js/ast/JsVisitor.java

@@ -8,10 +8,7 @@ import com.google.dart.compiler.backend.js.ast.JsVars.JsVar;
 
 import java.util.List;
 
-/**
+public abstract class JsVisitor {
- * Implemented by nodes that will visit child nodes.
- */
-abstract public class JsVisitor {
     protected static final JsContext LVALUE_CONTEXT = new JsContext() {
         @Override
         public boolean canInsert() {
@@ -24,12 +21,12 @@ abstract public class JsVisitor {
         }
 
         @Override
-        public void insertAfter(JsVisitable node) {
+        public void insertAfter(JsNode node) {
             throw new UnsupportedOperationException();
         }
 
         @Override
-        public void insertBefore(JsVisitable node) {
+        public void insertBefore(JsNode node) {
             throw new UnsupportedOperationException();
         }
 
@@ -44,13 +41,12 @@ abstract public class JsVisitor {
         }
 
         @Override
-        public void replaceMe(JsVisitable node) {
+        public void replaceMe(JsNode node) {
             throw new UnsupportedOperationException();
         }
     };
 
     protected static final JsContext UNMODIFIABLE_CONTEXT = new JsContext() {
-
         @Override
         public boolean canInsert() {
             return false;
@@ -62,12 +58,12 @@ abstract public class JsVisitor {
         }
 
         @Override
-        public void insertAfter(JsVisitable node) {
+        public void insertAfter(JsNode node) {
             throw new UnsupportedOperationException();
         }
 
         @Override
-        public void insertBefore(JsVisitable node) {
+        public void insertBefore(JsNode node) {
             throw new UnsupportedOperationException();
         }
 
@@ -82,17 +78,17 @@ abstract public class JsVisitor {
         }
 
         @Override
-        public void replaceMe(JsVisitable node) {
+        public void replaceMe(JsNode node) {
             throw new UnsupportedOperationException();
         }
     };
 
-    public <T extends JsVisitable> T accept(T node) {
+    public <T extends JsNode> T accept(T node) {
         doTraverse(node, UNMODIFIABLE_CONTEXT);
         return node;
     }
 
-    public final <T extends JsVisitable> void acceptList(List<T> collection) {
+    public final <T extends JsNode> void acceptList(List<T> collection) {
         for (T node : collection) {
             doTraverse(node, UNMODIFIABLE_CONTEXT);
         }
@@ -103,138 +99,12 @@ abstract public class JsVisitor {
         return expr;
     }
 
-    public final <T extends JsVisitable> void acceptWithInsertRemove(List<T> collection) {
+    public final <T extends JsNode> void acceptWithInsertRemove(List<T> collection) {
         for (T node : collection) {
             doTraverse(node, UNMODIFIABLE_CONTEXT);
         }
     }
 
-    public void endVisit(JsArrayAccess x, JsContext ctx) {
-    }
-
-    public void endVisit(JsArrayLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsBinaryOperation x, JsContext ctx) {
-    }
-
-    public void endVisit(JsBlock x, JsContext ctx) {
-    }
-
-    public void endVisit(JsLiteral.JsBooleanLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsBreak x, JsContext ctx) {
-    }
-
-    public void endVisit(JsCase x, JsContext ctx) {
-    }
-
-    public void endVisit(JsCatch x, JsContext ctx) {
-    }
-
-    public void endVisit(JsConditional x, JsContext ctx) {
-    }
-
-    public void endVisit(JsContinue x, JsContext ctx) {
-    }
-
-    public void endVisit(JsDebugger x, JsContext ctx) {
-    }
-
-    public void endVisit(JsDefault x, JsContext ctx) {
-    }
-
-    public void endVisit(JsDoWhile x, JsContext ctx) {
-    }
-
-    public void endVisit(JsEmpty x, JsContext ctx) {
-    }
-
-    public void endVisit(JsExpressionStatement x, JsContext ctx) {
-    }
-
-    public void endVisit(JsFor x, JsContext ctx) {
-    }
-
-    public void endVisit(JsForIn x, JsContext ctx) {
-    }
-
-    public void endVisit(JsFunction x, JsContext ctx) {
-    }
-
-    public void endVisit(JsIf x, JsContext ctx) {
-    }
-
-    public void endVisit(JsInvocation x, JsContext ctx) {
-    }
-
-    public void endVisit(JsLabel x, JsContext ctx) {
-    }
-
-    public void endVisit(JsNameRef x, JsContext ctx) {
-    }
-
-    public void endVisit(JsNew x, JsContext ctx) {
-    }
-
-    public void endVisit(JsNullLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsNumberLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsObjectLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsParameter x, JsContext ctx) {
-    }
-
-    public void endVisit(JsPostfixOperation x, JsContext ctx) {
-    }
-
-    public void endVisit(JsPrefixOperation x, JsContext ctx) {
-    }
-
-    public void endVisit(JsProgram x, JsContext ctx) {
-    }
-
-    public void endVisit(JsProgramFragment x, JsContext ctx) {
-    }
-
-    public void endVisit(JsPropertyInitializer x, JsContext ctx) {
-    }
-
-    public void endVisit(JsRegExp x, JsContext ctx) {
-    }
-
-    public void endVisit(JsReturn x, JsContext ctx) {
-    }
-
-    public void endVisit(JsStringLiteral x, JsContext ctx) {
-    }
-
-    public void endVisit(JsSwitch x, JsContext ctx) {
-    }
-
-    public void endVisit(JsLiteral.JsThisRef x, JsContext ctx) {
-    }
-
-    public void endVisit(JsThrow x, JsContext ctx) {
-    }
-
-    public void endVisit(JsTry x, JsContext ctx) {
-    }
-
-    public void endVisit(JsVar x, JsContext ctx) {
-    }
-
-    public void endVisit(JsVars x, JsContext ctx) {
-    }
-
-    public void endVisit(JsWhile x, JsContext ctx) {
-    }
-
     public boolean visit(JsArrayAccess x, JsContext ctx) {
         return true;
     }
@@ -287,8 +157,7 @@ abstract public class JsVisitor {
         return true;
     }
 
-    public boolean visit(JsEmpty x, JsContext ctx) {
+    public void visit(JsEmpty x, JsContext ctx) {
-        return true;
     }
 
     public boolean visit(JsExpressionStatement x, JsContext ctx) {
@@ -327,16 +196,13 @@ abstract public class JsVisitor {
         return true;
     }
 
-    public boolean visit(JsNullLiteral x, JsContext ctx) {
+    public void visit(JsNullLiteral x, JsContext ctx) {
-        return true;
     }
 
-    public boolean visit(JsNumberLiteral.JsIntLiteral x, JsContext ctx) {
+    public void visit(JsNumberLiteral.JsIntLiteral x, JsContext ctx) {
-        return true;
     }
 
-    public boolean visit(JsNumberLiteral.JsDoubleLiteral x, JsContext ctx) {
+    public void visit(JsNumberLiteral.JsDoubleLiteral x, JsContext ctx) {
-        return true;
     }
 
     public boolean visit(JsObjectLiteral x, JsContext ctx) {
@@ -367,16 +233,14 @@ abstract public class JsVisitor {
         return true;
     }
 
-    public boolean visit(JsRegExp x, JsContext ctx) {
+    public void visit(JsRegExp x, JsContext ctx) {
-        return true;
     }
 
     public boolean visit(JsReturn x, JsContext ctx) {
         return true;
     }
 
-    public boolean visit(JsStringLiteral x, JsContext ctx) {
+    public void visit(JsStringLiteral x, JsContext ctx) {
-        return true;
     }
 
     public boolean visit(JsSwitch x, JsContext ctx) {
@@ -411,7 +275,7 @@ abstract public class JsVisitor {
         return true;
     }
 
-    protected void doTraverse(JsVisitable node, JsContext context) {
+    protected void doTraverse(JsNode node, JsContext context) {
-        node.traverse(this, context);
+        node.accept(this, context);
     }
 }

src/com/google/dart/compiler/backend/js/ast/JsWhile.java

@@ -36,12 +36,14 @@ public class JsWhile extends JsNodeImpl implements JsStatement {
     }
 
     @Override
-    public void traverse(JsVisitor v, JsContext context) {
+    public void accept(JsVisitor v, JsContext context) {
-        if (v.visit(this, context)) {
+        v.visit(this, context);
-            condition = v.accept(condition);
-            body = v.accept(body);
     }
-        v.endVisit(this, context);
+
+    @Override
+    public void acceptChildren(JsVisitor visitor, JsContext context) {
+        condition = visitor.accept(condition);
+        body = visitor.accept(body);
     }
 
     @Override

src/com/google/dart/compiler/backend/js/ast/RecursiveJsVisitor.java

@@ -0,0 +1,4 @@
+package com.google.dart.compiler.backend.js.ast;
+
+public abstract class RecursiveJsVisitor extends JsVisitor {
+}