dart2js crash in inference: JS-interop + field + function types

[sigmundch]

This program is invalid because the field in class B should be declared as an external getter/setter:

@JS()
import 'package:js/js.dart';

@JS()
@anonymous
class B {
  int Function() callback;
}

external B makeB();

main() {
  makeB().callback();
}

Today it produces this crash in the compiler:

The compiler crashed: NoSuchMethodError: Class 'FunctionType' has no instance getter 'element'.
Receiver: Instance of 'FunctionType'
Tried calling: element
#0      Object.noSuchMethod (dart:core/runtime/libobject_patch.dart:46:5)
#1      InferrerEngineImpl.typeOfNativeBehavior (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/inferrer_engine.dart:383:48)
#2      FieldTypeInformation.handleSpecialCases (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart:540:12)
#3      MemberTypeInformation.computeType (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart:487:29)
#4      TypeInformation.refine (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart:149:54)
#5      InferrerEngineImpl.refine (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/inferrer_engine.dart:792:36)
#6      InferrerEngineImpl.runOverAllElements (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/inferrer_engine.dart:489:5)
#7      TypeGraphInferrer.analyzeMain (file:///path/to/sdk/sdk/pkg/compiler/lib/src/inferrer/type_graph_inferrer.dart:67:14)
#8      GlobalTypeInferenceTask.runGlobalTypeInference.<anonymous closure> (file:///path/to/sdk/sdk/pkg/compiler/lib/src/types/types.dart:233:29)
#9      CompilerTask.measure (file:///path/to/sdk/sdk/pkg/compiler/lib/src/common/tasks.dart:63:51)
#10     GlobalTypeInferenceTask.runGlobalTypeInference (file:///path/to/sdk/sdk/pkg/compiler/lib/src/types/types.dart:229:12)
#11     Compiler.performGlobalTypeInference (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:383:28)
#12     Compiler.compileLoadedLibraries.<anonymous closure> (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:424:15)
#13     CompilerTask.measureSubtask (file:///path/to/sdk/sdk/pkg/compiler/lib/src/common/tasks.dart:178:35)
#14     Compiler.compileLoadedLibraries (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:420:16)
#15     Compiler.runInternal (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:297:5)
<asynchronous suspension>
#16     Compiler.run.<anonymous closure>.<anonymous closure> (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:223:38)
#17     new Future.sync (dart:async/future.dart:222:31)
#18     Compiler.run.<anonymous closure> (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:223:20)
#19     CompilerTask.measureSubtask (file:///path/to/sdk/sdk/pkg/compiler/lib/src/common/tasks.dart:178:35)
#20     Compiler.run (file:///path/to/sdk/sdk/pkg/compiler/lib/src/compiler.dart:220:41)
#21     CompilerImpl.run.<anonymous closure>.<anonymous closure> (file:///path/to/sdk/sdk/pkg/compiler/lib/src/apiimpl.dart:148:22)
#22     _RootZone.runUnary (dart:async/zone.dart:1381:54)
#23     _FutureListener.handleValue (dart:async/future_impl.dart:129:18)
#24     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:638:45)
#25     Future._propagateToListeners (dart:async/future_impl.dart:667:32)
#26     Future._addListener.<anonymous closure> (dart:async/future_impl.dart:347:9)
#27     _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
#28     _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
#29     _runPendingImmediateCallback (dart:isolate/runtime/libisolate_patch.dart:113:13)
#30     _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:166:5)

Finished with a exit code: 253