Fix analyzer's handling of import prefixes not followed by '.'.

pkg/analyzer/lib/src/generated/error.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 engine.error;
 
 import 'dart:collection';
 
 import 'ast.dart' show AstNode;
 import 'element.dart';
@@ skipping 1931 matching lines @@
 
   /**
    * 14.1 Imports: It is a compile-time error if the current library declares a
    * top-level member named <i>p</i>.
    */
   static const CompileTimeErrorCode PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER =
       const CompileTimeErrorCode('PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER',
           "The name '{0}' is already used as an import prefix and cannot be used to name a top-level element");
 
   /**
+   * 16.32 Identifier Reference: If d is a prefix p, a compile-time error
+   * occurs unless the token immediately following d is '.'.
+   */
+  static const CompileTimeErrorCode PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT =
+      const CompileTimeErrorCode('PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT',
+          "The name '{0}' refers to an import prefix, so it must be followed by '.'");
+
+  /**
    * 6.2.2 Optional Formals: It is a compile-time error if the name of a named
    * optional parameter begins with an '_' character.
    */
   static const CompileTimeErrorCode PRIVATE_OPTIONAL_PARAMETER =
       const CompileTimeErrorCode('PRIVATE_OPTIONAL_PARAMETER',
           "Named optional parameters cannot start with an underscore");
 
   /**
    * 12.1 Constants: It is a compile-time error if the value of a compile-time
    * constant expression depends on itself.
@@ skipping 2968 matching lines @@
    * Initialize a newly created error code to have the given [name].
    */
   const TodoCode(String name) : super(name, "{0}");
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.INFO;
 
   @override
   ErrorType get type => ErrorType.TODO;
 }