Emit classes using ASTs

sdk/lib/_internal/compiler/implementation/code_buffer.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.
 
 part of dart2js;
 
 class CodeBuffer implements StringBuffer {
   StringBuffer buffer;
   List<CodeBufferMarker> markers;
   int lastBufferOffset = 0;
@@ skipping 27 matching lines @@
       CodeBufferMarker firstMarker = other.markers[0];
       int offsetDelta =
           buffer.length + firstMarker.offsetDelta - lastBufferOffset;
       markers.add(new CodeBufferMarker(offsetDelta,
                                        firstMarker.sourcePosition));
       for (int i = 1; i < other.markers.length; ++i) {
         markers.add(other.markers[i]);
       }
       lastBufferOffset = buffer.length + other.lastBufferOffset;
     }
-    buffer.add(other.toString());
+    buffer.add(other.getText());
   }
 
   CodeBuffer addAll(Collection<Object> objects) {
     for (Object obj in objects) {
       add(obj);
     }
     return this;
   }
 
   CodeBuffer addCharCode(int charCode) {
     return add(new String.fromCharCodes([charCode]));
   }
 
   CodeBuffer clear() {
     buffer.clear();
     markers.clear();
     lastBufferOffset = 0;
     return this;
   }
 
   String toString() {
+    throw "Don't use CodeBuffer.toString() since it drops sourcemap data.";
+  }
+
+  String getText() {
     return buffer.toString();
   }
 
   void beginMappedRange() {
     ++mappedRangeCounter;
   }
 
   void endMappedRange() {
     assert(mappedRangeCounter > 0);
     --mappedRangeCounter;
@@ skipping 13 matching lines @@
     });
   }
 }
 
 class CodeBufferMarker {
   final int offsetDelta;
   final sourcePosition;
 
   CodeBufferMarker(this.offsetDelta, this.sourcePosition);
 }