fix for index operation unparses

lib/compiler/implementation/tree/unparser.dart

Index: lib/compiler/implementation/tree/unparser.dart
diff --git a/lib/compiler/implementation/tree/unparser.dart b/lib/compiler/implementation/tree/unparser.dart
index 05b24260254451bb67f314f740ba13b5e4956b95..2ee401b1d781e7261b6680f2c9d3aff17f59f877 100644
--- a/lib/compiler/implementation/tree/unparser.dart
+++ b/lib/compiler/implementation/tree/unparser.dart
@@ -179,7 +179,6 @@ class Unparser implements Visitor {
     if (node.endToken !== null) add(node.endToken.value);
   }
 
-
   unparseSendPart(Send node) {
     if (node.isPrefix) {
       visit(node.selector);
@@ -188,7 +187,7 @@ class Unparser implements Visitor {
       visit(node.receiver);
       if (node.selector is !Operator) sb.add('.');
     }
-    if (!node.isPrefix) {
+    if (!node.isPrefix && !node.isIndex) {
       visit(node.selector);
     }
   }
@@ -198,10 +197,27 @@ class Unparser implements Visitor {
     visit(node.argumentsNode);
   }
 
-  visitSendSet(SendSet node) {
-    unparseSendPart(node);
+  // Special case for assignments like "list[0] = 1".

[ahe, 2012/05/30 10:03:12]

This should be a doc comment.

[Roman, 2012/05/30 10:44:04]

Done.

+  visitListIndexSet(SendSet node) {

[ahe, 2012/05/30 10:03:12]

This is not a visitor method. So it should be named for it it does. For example:

unparseIndexedSet

[Roman, 2012/05/30 10:44:04]

Done.

+    visit(node.receiver);
+    sb.add('[');
+    sb.add(node.arguments.head);
+    sb.add(']');
     add(node.assignmentOperator.token.value);
-    visit(node.argumentsNode);
+    NodeList tailArguments = new NodeList(

[Roman, 2012/05/30 09:09:55]

not sure about this one. beginToken and endToken would be incorrect, but we need
to unparse the rest of arguments.

[ahe, 2012/05/30 10:03:12]

I don't like constructing fake AST nodes just for unparsing. How about:

String delimiter = (node.argumentsNode.delimiter === null) ? " " :
"${node.argumentsNode.delimiter} ";

node.argumentsNode.nodes.tail.printOn(sb, delimiter);

You could possibly share this with visitNodeList.

[Roman, 2012/05/30 10:44:04]

Done.

+        node.argumentsNode.beginToken, node.argumentsNode.nodes.tail,
+        node.argumentsNode.endToken, node.argumentsNode.delimiter);
+    visit(tailArguments);
+  }
+
+  visitSendSet(SendSet node) {
+    if (node.isIndex) {
+      visitListIndexSet(node);
+    } else {
+      unparseSendPart(node);
+      add(node.assignmentOperator.token.value);
+      visit(node.argumentsNode);
+    }
   }
 
   visitThrow(Throw node) {