Make the ClosedWorld build the closure class on the kernel side.

pkg/compiler/lib/src/common/codegen.dart

 // Copyright (c) 2012, 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 dart2js.common.codegen;
 
 import '../common_elements.dart';
 import '../elements/elements.dart' show LocalFunctionElement;
 import '../elements/entities.dart';
 import '../elements/types.dart' show DartType, InterfaceType;
@@ skipping 129 matching lines @@
 
   void registerConstantUse(ConstantUse constantUse) {
     worldImpact.registerConstantUse(constantUse);
   }
 
   void registerTypeVariableBoundsSubtypeCheck(
       DartType subtype, DartType supertype) {
     worldImpact.registerTypeVariableBoundsSubtypeCheck(subtype, supertype);
   }
 
-  void registerInstantiatedClosure(LocalFunctionElement element) {
+  void registerInstantiatedClosure(Local element) {

[sra1, 2017/07/28 20:38:51]

assert this is a function that can be used to find the synthetic closure class

[Emily Fortuna, 2017/07/28 21:37:06]

You're right, this isn't an easy fix. I put it back to LocalFunctionElement and
updated the status file.

Johnni, can you please take a look at this? Basically we have a JLocal, but a
little further on we expect it to be a KLocalFunction (and it would be nice to
be sure that the thing passed in is a form of LocalFunction rather than just a
Local). I'm not sure if this is due to not having propagated K->J throughout the
backend or if I should be storing a different local type for the "original"
closure.

[Johnni Winther, 2017/07/31 10:54:28]

It is okay to use [Local] here. Long term we should just register the
call-method instead (we use it to compute if the signature is needed for RTI).

     worldImpact.registerStaticUse(new StaticUse.closure(element));
   }
 
   void registerConstSymbol(String name) {
     worldImpact.registerConstSymbol(name);
   }
 
   void registerSpecializedGetInterceptor(Set<ClassEntity> classes) {
     worldImpact.registerSpecializedGetInterceptor(classes);
   }
 
   void registerUseInterceptor() {
     worldImpact.registerUseInterceptor();
   }
 
   void registerInstantiation(InterfaceType type) {
     registerTypeUse(new TypeUse.instantiation(type));
   }
 
   void registerAsyncMarker(AsyncMarker asyncMarker) {
     worldImpact.registerAsyncMarker(asyncMarker);
   }
 }
 
 /// [WorkItem] used exclusively by the [CodegenEnqueuer].
 abstract class CodegenWorkItem extends WorkItem {
   CodegenRegistry get registry;
 }