Use as dynamic to get rid of warnigns in code_transformers

pkg/code_transformers/lib/src/dart_sdk.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 code_transformers.src.dart_sdk;
 
 import 'dart:convert' as convert;
 import 'dart:io' show File, Platform, Process;
 import 'package:path/path.dart' as path;
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 90 matching lines @@
   final Source _proxy;
 
   DartSourceProxy(this._proxy, this.uri);
 
   /// Ensures that [source] is a DartSourceProxy.
   static DartSourceProxy wrap(Source source, Uri uri) {
     if (source == null || source is DartSourceProxy) return source;
     return new DartSourceProxy(source, uri);
   }
 
+  // Note: to support both analyzer versions <0.22.0 and analyzer >=0.22.0, we
+  // implement both `resolveRelative` and `resolveRelativeUri`. Only one of them
+  // is available at a time in the analyzer package, so we use the `as dynamic`
+  // in these methods to hide warnings for the code that is missing. These APIs
+  // are invoked from the analyzer itself, so we don't expect them to cause
+  // failures.
   Source resolveRelative(Uri relativeUri) {
     // Assume that the type can be accessed via this URI, since these
     // should only be parts for dart core files.
-    return wrap(_proxy.resolveRelative(relativeUri), uri);
+    return wrap((_proxy as dynamic).resolveRelative(relativeUri), uri);
   }
 
   Uri resolveRelativeUri(Uri relativeUri) {
-    return _proxy.resolveRelativeUri(relativeUri);
+    return (_proxy as dynamic).resolveRelativeUri(relativeUri);
   }
 
   bool exists() => _proxy.exists();
 
   bool operator ==(Object other) =>
     (other is DartSourceProxy && _proxy == other._proxy);
 
   int get hashCode => _proxy.hashCode;
 
   TimestampedData<String> get contents => _proxy.contents;
@@ skipping 88 matching lines @@
   UriKind get uriKind => UriKind.DART_URI;
 
   bool get isInSystemLibrary => true;
 
   Source resolveRelative(Uri relativeUri) =>
       throw new UnsupportedError('not expecting relative urls in dart: mocks');
 
   Uri resolveRelativeUri(Uri relativeUri) =>
       throw new UnsupportedError('not expecting relative urls in dart: mocks');
 }