Implement cycle-checking and code generation for redirecting constructors.

frog/leg/tree/nodes.dart

 // 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.
 
 interface Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCatchBlock(CatchBlock node);
   R visitClassNode(ClassNode node);
   R visitConditional(Conditional node);
@@ skipping 513 matching lines @@
 
   accept(Visitor visitor) => visitor.visitFunctionExpression(this);
 
   visitChildren(Visitor visitor) {
     if (name !== null) name.accept(visitor);
     if (parameters !== null) parameters.accept(visitor);
     if (body !== null) body.accept(visitor);
     if (returnType !== null) returnType.accept(visitor);
   }
 
+  bool hasBody() {
+    if (body.asReturn() !== null) return true;
+    NodeList statements = body.asBlock().statements;
+    return (!statements.nodes.isEmpty() ||
+            statements.getBeginToken().kind !== $SEMICOLON);
+  }
+
   Token getBeginToken() {
     Token token = firstBeginToken(modifiers, returnType);
     if (token !== null) return token;
     if (getOrSet !== null) return getOrSet;
     return firstBeginToken(name, parameters);
   }
 
   Token getEndToken() {
     return (body === null) ? parameters.getEndToken() : body.getEndToken();
   }
@@ skipping 922 matching lines @@
   static bool isConstructorRedirect(Send node) {
     return (node.receiver === null &&
             node.selector.asIdentifier() !== null &&
             node.selector.asIdentifier().isThis()) ||
            (node.receiver !== null &&
             node.receiver.asIdentifier() !== null &&
             node.receiver.asIdentifier().isThis() &&
             node.selector.asIdentifier() !== null);
   }
 }