Disallow opening of directories as files.

tests/standalone/src/FileTest.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.
 //
 // Dart test program for testing file I/O.
 
 #import("dart:io");
 
 class FileTest {
   static Directory tempDirectory;
@@ skipping 717 matching lines @@
       try {
         f.existsSync();
         Expect.fail("Expected exception");
       } catch (var e) {
         Expect.isTrue(e is FileIOException);
       }
     };
     f.exists();
   }
 
+  static void testOpenDirectoryAsFile() {
+    var f = new File('.');
+    f.open();
+    f.openHandler = (r) => Expect.fail('Directory opened as file');
+  }
+
+  static void testOpenDirectoryAsFileSync() {
+    var f = new File('.');
+    try {
+      f.openSync();
+      Expect.fail("Expected exception opening directory as file");
+    } catch (var e) {
+      Expect.isTrue(e is FileIOException);
+    }
+  }
+
   // Test that opens the same file for writing then for appending to test
   // that the file is not truncated when opened for appending.
   static void testAppend() {
     var file = new File('${tempDirectory.path}/out_append');
     file.openHandler = (openedFile) {
       openedFile.noPendingWriteHandler = () {
         openedFile.closeHandler = () {
           file.openHandler = (openedFile) {
             openedFile.lengthHandler = (length) {
               Expect.equals(4, length);
@@ skipping 54 matching lines @@
   // Main test entrypoint.
   static testMain() {
     testRead();
     testReadSync();
     testReadStream();
     testLength();
     testLengthSync();
     testPosition();
     testPositionSync();
     testMixedSyncAndAsync();
+    testOpenDirectoryAsFile();
+    testOpenDirectoryAsFileSync();
 
     createTempDirectory(() {
         testReadWrite();
         testReadWriteSync();
         testReadWriteStream();
         testReadEmptyFileSync();
         testReadEmptyFile();
         testTruncate();
         testTruncateSync();
         testCloseException();
         testCloseExceptionStream();
         testBufferOutOfBoundsException();
         testAppend();
         testAppendSync();
         testWriteAppend();
         testOutputStreamWriteAppend();
       });
   }
 }
 
 main() {
   FileTest.testMain();
 }