Make first and last getters.

lib/compiler/implementation/js/printer.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 Printer implements NodeVisitor {
   final bool shouldCompressOutput;
   leg.Compiler compiler;
   leg.CodeBuffer outBuffer;
   int indentLevel = 0;
   bool inForInit = false;
@@ skipping 960 matching lines @@
       var codes = <int>[];
       for (var i = 0; i < alphaChars; i++) {
         nameSpaceSize ~/= LETTERS;
         codes.add(nthLetter((n ~/ nameSpaceSize) % LETTERS));
       }
       codes.add(charCodes.$0 + digit);
       newName = new String.fromCharCodes(codes);
     }
     assert(const RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
     nameNumber++;
-    maps.last()[oldName] = newName;
+    maps.last[oldName] = newName;
     return newName;
   }
 }