Start new design for interceptors and implement String.charCodeAt with it.

sdk/lib/_internal/compiler/implementation/lib/interceptors.dart

Index: sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/lib/interceptors.dart	(revision 14732)
+++ sdk/lib/_internal/compiler/implementation/lib/interceptors.dart	(working copy)
@@ -6,6 +6,25 @@
 
 #import('dart:collection');
 
+class JSString implements String {

[ahe, 2012/11/12 13:24:11]

Consider moving this to its own file.

[ahe, 2012/11/12 13:24:11]

Document this class.

[ngeoffray, 2012/11/13 11:45:16]

In the long run, this file will only contain interceptor classes.

[ngeoffray, 2012/11/13 11:45:16]

Done.

+  const JSString();
+  int charCodeAt(index) {

[ahe, 2012/11/12 13:24:11]

Add a newline between declarations.

[ngeoffray, 2012/11/13 11:45:16]

Done.

+    if (index is !num) throw new ArgumentError(index);
+    if (index < 0) throw new RangeError.value(index);
+    if (index >= length) throw new RangeError.value(index);
+    return JS('int', r'#.charCodeAt(#)', this, index);
+  }
+}
+
+class ObjectInterceptor {

[ahe, 2012/11/12 13:24:11]

Document this class.  Explain that all its members are synthesized by the
emitter.

[ngeoffray, 2012/11/13 11:45:16]

Done.

+  const ObjectInterceptor();
+}
+
+getInterceptor(obj) {

[ahe, 2012/11/12 13:24:11]

Document as well.

[ngeoffray, 2012/11/13 11:45:16]

Done.

+  if (obj is String) return const JSString();
+  return const ObjectInterceptor();
+}
+
 add$1(var receiver, var value) {
   if (isJsArray(receiver)) {
     checkGrowable(receiver, 'add');
@@ -90,17 +109,6 @@
   return UNINTERCEPTED(receiver.iterator());
 }
 
-charCodeAt(var receiver, int index) {
-  if (receiver is String) {
-    if (index is !num) throw new ArgumentError(index);
-    if (index < 0) throw new RangeError.value(index);
-    if (index >= receiver.length) throw new RangeError.value(index);
-    return JS('int', r'#.charCodeAt(#)', receiver, index);
-  } else {
-    return UNINTERCEPTED(receiver.charCodeAt(index));
-  }
-}
-
 get$isEmpty(receiver) {
   if (receiver is String || isJsArray(receiver)) {
     return JS('bool', r'#.length === 0', receiver);