dart2js: check for the full getter/setter prefixes (fix #23828)

pkg/compiler/lib/src/js_emitter/full_emitter/nsm_emitter.dart

 // Copyright (c) 2013, 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.js_emitter.full_emitter;
 
 class NsmEmitter extends CodeEmitterHelper {
   final List<Selector> trivialNsmHandlers = <Selector>[];
 
   /// If this is true then we can generate the noSuchMethod handlers at startup
@@ skipping 219 matching lines @@
             : js('j < #', js.number(interceptedSelectors.length));
 
     statements.add(js.statement('''
       // If we are loading a deferred library the object class will not be in
       // the collectedClasses so objectClassObject is undefined, and we skip
       // setting up the names.
       if (objectClassObject) {
         for (var j = 0; j < shortNames.length; j++) {
           var type = 0;
           var shortName = shortNames[j];
-          if (shortName[0] == "${namer.getterPrefix[0]}") type = 1;
-          if (shortName[0] == "${namer.setterPrefix[0]}") type = 2;
+          if (shortName.indexOf("${namer.getterPrefix}") == 0) type = 1;
+          if (shortName.indexOf("${namer.setterPrefix}") == 0) type = 2;
           // Generate call to:
           //
           //     createInvocationMirror(String name, internalName, type,
           //         arguments, argumentNames)
           //
 
           // This 'if' is either a static choice or dynamic choice depending on
           // [isIntercepted].
           if (#isIntercepted) {
             objectClassObject[shortName] =
@@ skipping 130 matching lines @@
   }
 
   String get value {
     if (_cachedValue == null) {
       _cachedValue = _computeDiffEncoding();
     }
 
     return _cachedValue;
   }
 }