Change executable name to "darfmt". Fix #163.

lib/src/source_visitor.dart

 // Copyright (c) 2014, 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.
 
 library dart_style.src.source_visitor;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/source.dart';
 
@@ skipping 1112 matching lines @@
     token(node.period);
     visit(node.identifier);
   }
 
   visitPrefixExpression(PrefixExpression node) {
     token(node.operator);
 
     // Corner case: put a space between successive "-" operators so we don't
     // inadvertently turn them into a "--" decrement operator.
     if (node.operand is PrefixExpression &&
-        node.operand.operator.lexeme == "-") {
+        (node.operand as PrefixExpression).operator.lexeme == "-") {
       space();
     }
 
     visit(node.operand);
   }
 
   visitPropertyAccess(PropertyAccess node) {
     if (node.isCascaded) {
       token(node.operator);
     } else {
@@ skipping 787 matching lines @@
   /// Gets the 1-based line number that the beginning of [token] lies on.
   int _startLine(Token token) => _lineInfo.getLocation(token.offset).lineNumber;
 
   /// Gets the 1-based line number that the end of [token] lies on.
   int _endLine(Token token) => _lineInfo.getLocation(token.end).lineNumber;
 
   /// Gets the 1-based column number that the beginning of [token] lies on.
   int _startColumn(Token token) =>
       _lineInfo.getLocation(token.offset).columnNumber;
 }