Issue 22845. Rename should prevent the use of invalid identifiers.

pkg/analysis_server/lib/src/services/refactoring/naming_conventions.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 services.src.refactoring.naming_conventions;
 
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:analysis_server/src/services/correction/strings.dart';
+import 'package:analyzer/src/generated/scanner.dart';
 
 /**
  * Returns the [RefactoringStatus] with severity:
  *   OK if the name is valid;
  *   WARNING if the name is discouraged;
  *   FATAL if the name is illegal.
  */
 RefactoringStatus validateClassName(String name) {
   return _validateUpperCamelCase(name, "Class");
 }
@@ skipping 138 matching lines @@
   if (identifier != trimmed) {
     String message = "$desc must not start or end with a blank.";
     return new RefactoringStatus.fatal(message);
   }
   // empty
   int length = identifier.length;
   if (length == 0) {
     String message = "$desc must not be empty.";
     return new RefactoringStatus.fatal(message);
   }
+  // keyword
+  {
+    Keyword keyword = Keyword.keywords[identifier];
+    if (keyword != null && !keyword.isPseudoKeyword) {
+      String message = "$desc must not be a keyword.";
+      return new RefactoringStatus.fatal(message);
+    }
+  }
+  // first character
   int currentChar = identifier.codeUnitAt(0);
   if (!isLetter(currentChar) &&
       currentChar != CHAR_UNDERSCORE &&
       currentChar != CHAR_DOLLAR) {
     String message = "$desc must begin with $beginDesc.";
     return new RefactoringStatus.fatal(message);
   }
+  // other characters
   for (int i = 1; i < length; i++) {
     currentChar = identifier.codeUnitAt(i);
     if (!isLetterOrDigit(currentChar) &&
         currentChar != CHAR_UNDERSCORE &&
         currentChar != CHAR_DOLLAR) {
       String charStr = new String.fromCharCode(currentChar);
       String message = "$desc must not contain '$charStr'.";
       return new RefactoringStatus.fatal(message);
     }
   }
+  // OK
   return new RefactoringStatus();
 }
 
 /**
  * Validates [identifier], should be lower camel case.
  */
 RefactoringStatus _validateLowerCamelCase(String identifier, String desc) {
   desc += ' name';
   // null
   if (identifier == null) {
@@ skipping 49 matching lines @@
   }
   // does not start with upper case
   if (!isUpperCase(identifier.codeUnitAt(0))) {
     // By convention, class names usually start with an uppercase letter
     String message = "$desc should start with an uppercase letter.";
     return new RefactoringStatus.warning(message);
   }
   // OK
   return new RefactoringStatus();
 }