Avoid crashing on synthetic elements.

lib/kernel.dart

 // Copyright (c) 2016, 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.md file.
 
 library rasta.kernel;
 
 import 'dart:async' show
     Future;
 
 import 'dart:collection' show
@@ skipping 556 matching lines @@
       }
       if (irLibrary != null) {
         result.add(irLibrary);
       }
     }
     return result;
   }
 
   /// Returns true if [element] is synthesized to recover or represent a
   /// semantic error, for example, missing, duplicated, or ambiguous elements.
-  /// However, returns true for elements that have an unrecoverable syntax
+  /// However, returns false for elements that have an unrecoverable syntax
   /// error. Both kinds of element will return true from [Element.isMalformed],
   /// but they must be handled differently. For example, a static call to
   /// synthetic error element should be compiled to [ir.InvalidExpression],
   /// whereas a static call to a method which has a syntax error should be
   /// compiled to a static call to the method. The method itself will have a
   /// method body that is [ir.InvalidStatement].
   bool isSyntheticError(Element element) {
     if (element.isAmbiguous) return true;
     if (element.isError) return true;
     if (element.isField && element is ErroneousFieldElementX) {
@@ skipping 77 matching lines @@
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final DartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }