Finish strong mode cleaning of dart2js.

pkg/compiler/lib/src/inferrer/locals_handler.dart

 // Copyright (c) 2013, 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 locals_handler;
 
 import 'dart:collection' show IterableMixin;
 
 import '../options.dart' show CompilerOptions;
 import '../elements/elements.dart';
@@ skipping 173 matching lines @@
 
   String toString() => "{ positional = $positional, named = $named }";
 
   bool operator ==(other) {
     if (positional.length != other.positional.length) return false;
     if (named.length != other.named.length) return false;
     for (int i = 0; i < positional.length; i++) {
       if (positional[i] != other.positional[i]) return false;
     }
     named.forEach((name, type) {
+      // TODO(ahe): This is a bug.

[ahe, 2017/06/15 09:36:39]

I'll file an issue about this and update the comment.

[ahe, 2017/06/15 11:41:57]

Done.

+      // ignore: RETURN_OF_INVALID_TYPE
       if (other.named[name] != type) return false;
     });
     return true;
   }
 
   int get hashCode => throw new UnsupportedError('ArgumentsTypes.hashCode');
 
   bool hasNoArguments() => positional.isEmpty && named.isEmpty;
 
   void forEach(void f(TypeInformation type)) {
@@ skipping 339 matching lines @@
       if (newType != type) {
         locals[variable] = newType;
       }
     });
   }
 
   void updateField(Element element, TypeInformation type) {
     fieldScope.updateField(element, type);
   }
 }