Change how to set the Dart name of a field

lib/extension_generator.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 protoc;
 
 class ExtensionGenerator {
   final FieldDescriptorProto _descriptor;
   final ProtobufContainer _parent;
 
   // populated by resolve()
   ProtobufField _field;
+  String _extensionName;
   String _extendedClassName = "";
 
   ExtensionGenerator(this._descriptor, this._parent);
 
   void resolve(GenerationContext ctx) {
-    _field = new ProtobufField(_descriptor, null, _parent, ctx);
+    _extensionName = extensionName(_descriptor);
+    _field = new ProtobufField.extension(_descriptor, _parent, ctx);
 
     ProtobufContainer extendedType = ctx.getFieldType(_descriptor.extendee);
     // TODO(skybrian) When would this be null?
     if (extendedType != null) {
       _extendedClassName = extendedType.classname;
     }
   }
 
   String get package => _parent.package;
 
   /// The generator of the .pb.dart file where this extension will be defined.
   FileGenerator get fileGen => _parent.fileGen;
 
   String get name {
     if (_field == null) throw new StateError("resolve not called");
-    String name = _field.dartFieldName;
+    String name = _extensionName;
     return _parent is MessageGenerator ? '${_parent.classname}.$name' : name;
   }
 
   bool get needsFixnumImport {
     if (_field == null) throw new StateError("resolve not called");
     return _field.needsFixnumImport;
   }
 
   /// Adds dependencies of [generate] to [imports].
   ///
@@ skipping 20 matching lines @@
   /// For each .pb.dart file that the generated code needs to import,
   /// add its generator.
   void addConstantImportsTo(Set<FileGenerator> imports) {
     if (_field == null) throw new StateError("resolve not called");
     // No dependencies - nothing to do.
   }
 
   void generate(IndentingWriter out) {
     if (_field == null) throw new StateError("resolve not called");
 
-    String name = _field.dartFieldName;
+    String name = _extensionName;
     var type = _field.baseType;
     var dartType = type.getDartType(package);
 
     if (_field.isRepeated) {
       out.print('static final Extension $name = '
           'new Extension<$dartType>.repeated(\'$_extendedClassName\','
           ' \'$name\', ${_field.number}, ${_field.typeConstant}');
       if (type.isMessage || type.isGroup) {
         out.println(', $dartType.$checkItem, $dartType.create);');
       } else if (type.isEnum) {
@@ skipping 16 matching lines @@
       var dartEnum = type.getDartType(package);
       String valueOf = '(var v) => $dartEnum.valueOf(v)';
       out.println(", $initializer, null, $valueOf);");
     } else if (initializer != null) {
       out.println(", $initializer);");
     } else {
       out.println(");");
     }
   }
 }