Reapply "Minor adjustment to usage of the ClosureClassRepresentation interface."

pkg/compiler/lib/src/js_emitter/runtime_type_generator.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 dart2js.js_emitter.runtime_type_generator;
 
 import '../closure.dart'
     show ClosureRepresentationInfo, ClosureFieldElement, ClosureConversionTask;
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
@@ skipping 110 matching lines @@
       }
     }
 
     void generateFunctionTypeSignature(
         FunctionElement method, ResolutionFunctionType type) {
       assert(method.isImplementation);
       jsAst.Expression thisAccess = new jsAst.This();
       if (!method.isAbstract) {
         ClosureRepresentationInfo closureData =
             _closureDataLookup.getClosureRepresentationInfo(method);
-        if (closureData != null) {
+        if (closureData.isClosure && closureData.thisLocal != null) {

[Siggi Cherem (dart-lang), 2017/06/20 00:30:22]

is closureData never null now? Will it ever be the case that isClosure is false,
but thisLocal is true? If not, we could write this as:

if (closureData?.thisLocal != null) { ... }

           ClosureFieldElement thisLocal = closureData.thisFieldEntity;
-          if (thisLocal != null) {
-            jsAst.Name thisName = _namer.instanceFieldPropertyName(thisLocal);
-            thisAccess = js('this.#', thisName);
-          }
+          assert(thisLocal != null);
+          jsAst.Name thisName = _namer.instanceFieldPropertyName(thisLocal);
+          thisAccess = js('this.#', thisName);
         }
       }
 
       if (storeFunctionTypeInMetadata && !type.containsTypeVariables) {
         result.functionTypeIndex =
             emitterTask.metadataCollector.reifyType(type);
       } else {
         jsAst.Expression encoding = _rtiEncoder.getSignatureEncoding(
             emitterTask.emitter, type, thisAccess);
         jsAst.Name operatorSignature = _namer.asName(_namer.operatorSignature);
@@ skipping 194 matching lines @@
 
     // We need to also emit "is checks" for the superclass and its supertypes.
     ClassElement superclass = cls.superclass;
     if (superclass != null) {
       tryEmitTest(superclass);
       _generateInterfacesIsTests(
           superclass, generateIsTest, generateSubstitution, alreadyGenerated);
     }
   }
 }