Finish strong mode cleaning of dart2js.

pkg/compiler/lib/src/resolution/no_such_method_resolver.dart

 // Copyright (c) 2017, 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.
 
 import '../common/names.dart' show Identifiers, Names;
 import '../elements/elements.dart';
 import '../js_backend/no_such_method_registry.dart';
 import '../tree/tree.dart';
 
 /// AST-based implementation of [NoSuchMethodResolver].
@@ skipping 34 matching lines @@
     if (expr is Send &&
         expr.isSuperCall &&
         expr.selector is Identifier &&
         (expr.selector as Identifier).source == Identifiers.noSuchMethod_) {
       var arg = expr.arguments.head;
       if (expr.arguments.tail.isEmpty &&
           arg is Send &&
           arg.argumentsNode == null &&
           arg.receiver == null &&
           arg.selector is Identifier &&
+          // ignore: UNDEFINED_GETTER

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

Type of arg is *known* to be Send due to is test, so arg.selection has a known
type that has no source argument. I don't know how to fix this.

[Johnni Winther, 2017/06/15 10:21:26]

We probably need to nest ifs to make 'arg.selector' a local.

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

Done.

           arg.selector.source == param) {
         return true;
       }
     }
     return false;
   }
 
   bool hasThrowingSyntax(MethodElement element) {
     if (!element.hasResolvedAst) {
       // TODO(johnniwinther): Why do we see unresolved elements here?
@@ skipping 16 matching lines @@
         return stmt.expression is Throw;
       }
     }
     return false;
   }
 
   MethodElement getSuperNoSuchMethod(MethodElement method) {
     return method.enclosingClass.lookupSuperByName(Names.noSuchMethod_);
   }
 }