fix for index operation unparses

lib/compiler/implementation/tree/unparser.dart

 // Copyright (c) 2012, 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.
 
 class Unparser implements Visitor {
   StringBuffer sb;
   final bool printDebugInfo;
 
   Unparser([this.printDebugInfo = false]);
 
@@ skipping 161 matching lines @@
 
   visitReturn(Return node) {
     add(node.beginToken.value);
     if (node.hasExpression) {
       sb.add(' ');
       visit(node.expression);
     }
     if (node.endToken !== null) add(node.endToken.value);
   }
 
-
   unparseSendPart(Send node) {
     if (node.isPrefix) {
       visit(node.selector);
     }
     if (node.receiver !== null) {
       visit(node.receiver);
       if (node.selector is !Operator) sb.add('.');
     }
     if (!node.isPrefix) {
       visit(node.selector);
     }
   }
 
   visitSend(Send node) {
     unparseSendPart(node);
     visit(node.argumentsNode);
   }
 
+  // Special case for assignments like "list[0] = 1".
+  visitListIndexSet(SendSet node) {
+    visit(node.receiver);
+    sb.add('[');
+    sb.add(node.arguments.head);
+    sb.add(']');
+    add(node.assignmentOperator.token.value);
+    NodeList tailArguments = new NodeList(
+        node.argumentsNode.beginToken, node.argumentsNode.nodes.tail, node.argumentsNode.endToken,
+        node.argumentsNode.delimiter);
+    visit(tailArguments);
+  }
+
   visitSendSet(SendSet node) {
-    unparseSendPart(node);
-    add(node.assignmentOperator.token.value);
-    visit(node.argumentsNode);
+    Operator op = node.selector.asOperator();
+    bool isListIndex = op !== null && op.source.stringValue == '[]';

[Anton Muhin, 2012/05/24 16:59:58]

I believe we have exactly the same problem for expressions like l[0], e.g. var x
= l[0].  So solution should be in unparseSendPart

+    if (isListIndex) {
+      visitListIndexSet(node);
+    } else {
+      unparseSendPart(node);
+      add(node.assignmentOperator.token.value);
+      visit(node.argumentsNode);
+    }
   }
 
   visitThrow(Throw node) {
     add(node.throwToken.value);
     if (node.expression !== null) {
       sb.add(' ');
       visit(node.expression);
     }
     node.endToken.value.printOn(sb);
   }
@@ skipping 188 matching lines @@
       sb.add(' ');
     }
     visit(node.name);
     if (node.typeParameters !== null) {
       visit(node.typeParameters);
     }
     visit(node.formals);
     add(node.endToken.value);
   }
 }