Implement support for watching directories containing implicitly analyzed files

pkg/analyzer/lib/file_system/memory_file_system.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 memory_file_system;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core' hide Resource;
 
@@ skipping 90 matching lines @@
     newFolder(posix.dirname(path));
     _MemoryDummyLink link = new _MemoryDummyLink(this, path);
     _pathToResource[path] = link;
     _pathToTimestamp[path] = nextStamp++;
     _notifyWatchers(path, ChangeType.ADD);
     return link;
   }
 
   File newFile(String path, String content, [int stamp]) {
     path = posix.normalize(path);
-    newFolder(posix.dirname(path));
+    _MemoryResource resource = _pathToResource[path];
+    _MemoryResource folder = _pathToResource[posix.dirname(path)];
+    if (folder == null) {
+      newFolder(posix.dirname(path));
+    } else if (folder is! Folder) {
+      throw new ArgumentError('Cannot create file ($path) as child of file');
+    }
     _MemoryFile file = new _MemoryFile(this, path);
     _pathToResource[path] = file;
     _pathToContent[path] = content;
     _pathToTimestamp[path] = stamp != null ? stamp : nextStamp++;
     _notifyWatchers(path, ChangeType.ADD);
     return file;
   }
 
   Folder newFolder(String path) {
     path = posix.normalize(path);
     if (!path.startsWith('/')) {
       throw new ArgumentError("Path must start with '/'");
     }
     _MemoryResource resource = _pathToResource[path];
     if (resource == null) {
       String parentPath = posix.dirname(path);
       if (parentPath != path) {
         newFolder(parentPath);
       }
       _MemoryFolder folder = new _MemoryFolder(this, path);
       _pathToResource[path] = folder;
       _pathToTimestamp[path] = nextStamp++;
+      _notifyWatchers(path, ChangeType.ADD);
       return folder;
     } else if (resource is _MemoryFolder) {
+      _notifyWatchers(path, ChangeType.ADD);
       return resource;
     } else {
       String message =
           'Folder expected at ' "'$path'" 'but ${resource.runtimeType} found';
       throw new ArgumentError(message);
     }
   }
 
   File updateFile(String path, String content, [int stamp]) {
     path = posix.normalize(path);
@@ skipping 326 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }