fix for 1.12.0-dev SDK and 0.25.1 analyzer breaking changes

lib/src/info.dart

 // Copyright (c) 2015, 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.
 
 /// Defines static information collected by the type checker and used later by
 /// emitters to generate code.
 library dev_compiler.src.info;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 426 matching lines @@
   /// Whether the error comes from a mixin (either overriding a base class or an
   /// interface declaration).
   final bool fromMixin;
 
   InvalidOverride(
       AstNode node, this.element, this.base, this.subType, this.baseType)
       : fromBaseClass = node is ExtendsClause,
         fromMixin = node.parent is WithClause,
         super(node);
 
-  ClassDeclaration get parent =>
-      element.enclosingElement.node as ClassDeclaration;
+  ClassElement get parent => element.enclosingElement;

[Jennifer Messerly, 2015/07/09 17:03:29]

all we do here is get the name ... so we were potentially parsing again just to
get the class name ... ouch!

[vsm, 2015/07/09 17:09:56]

yikes - good catch!

 
   String _messageHelper(String errorName) {
     var name = element.name;
     var lcErrorName = errorName.toLowerCase();
     var intro = fromBaseClass
         ? 'Base class introduces an $lcErrorName'
         : (fromMixin ? 'Mixin introduces an $lcErrorName' : errorName);
     return '$intro. The type of ${parent.name}.$name ($subType) is not a '
         'subtype of $base.$name ($baseType).';
   }
@@ skipping 76 matching lines @@
     var isError = severity == ErrorSeverity.WARNING;
     var level = isError ? Level.SEVERE : Level.WARNING;
     int begin = error.offset;
     int end = begin + error.length;
     return new AnalyzerMessage(error.message, level, begin, end);
   }
 
   const AnalyzerMessage(String message, Level level, int begin, int end)
       : super(message, level, begin, end);
 }