Allow arity checks on dynamic function types

test/dart_codegen/expect/async/future_impl.dart

 part of dart.async;
  typedef dynamic _FutureOnValue<T>(T value);
  typedef bool _FutureErrorTest(var error);
  typedef _FutureAction();
  abstract class _Completer<T> implements Completer<T> {final _Future<T> future = new _Future<T>();
  void complete([value]);
  void completeError(Object error, [StackTrace stackTrace]) {
   error = _nonNullError(error);
    if (!future._mayComplete) throw new StateError("Future already completed");
    AsyncError replacement = Zone.current.errorCallback(error, stackTrace);
@@ skipping 40 matching lines @@
  _FutureListener.then(this.result, _FutureOnValue onValue, Function errorCallback) : callback = onValue, errorCallback = errorCallback, state = (errorCallback == null) ? STATE_THEN : STATE_THEN_ONERROR;
  _FutureListener.catchError(this.result, this.errorCallback, _FutureErrorTest test) : callback = test, state = (test == null) ? STATE_CATCHERROR : STATE_CATCHERROR_TEST;
  _FutureListener.whenComplete(this.result, _FutureAction onComplete) : callback = onComplete, errorCallback = null, state = STATE_WHENCOMPLETE;
  _FutureListener.chain(this.result) : callback = null, errorCallback = null, state = STATE_CHAIN;
  Zone get _zone => result._zone;
  bool get handlesValue => (state & MASK_VALUE != 0);
  bool get handlesError => (state & MASK_ERROR != 0);
  bool get hasErrorTest => (state == STATE_CATCHERROR_TEST);
  bool get handlesComplete => (state == STATE_WHENCOMPLETE);
  _FutureOnValue get _onValue {
-assert (handlesValue); return DEVC$RT.cast(callback, Function, __t14, "CastGeneral", """line 112, column 12 of dart:async/future_impl.dart: """, callback is __t14, false);
+assert (handlesValue); return DEVC$RT.cast(callback, Function, __t14, "CastGeneral", """line 112, column 12 of dart:async/future_impl.dart: """, callback is __t14, true);
 }
  Function get _onError => errorCallback;
  _FutureErrorTest get _errorTest {
 assert (hasErrorTest); return DEVC$RT.cast(callback, Function, __t16, "CastGeneral", """line 117, column 12 of dart:async/future_impl.dart: """, callback is __t16, false);
 }
  _FutureAction get _whenCompleteAction {
-assert (handlesComplete); return DEVC$RT.cast(callback, Function, __t18, "CastGeneral", """line 121, column 12 of dart:async/future_impl.dart: """, callback is __t18, false);
+assert (handlesComplete); return DEVC$RT.cast(callback, Function, __t18, "CastGeneral", """line 121, column 12 of dart:async/future_impl.dart: """, callback is __t18, true);
 }
 }
  class _Future<T> implements Future<T> {static const int _INCOMPLETE = 0;
  static const int _PENDING_COMPLETE = 1;
  static const int _CHAINED = 2;
  static const int _VALUE = 4;
  static const int _ERROR = 8;
  int _state = _INCOMPLETE;
  final Zone _zone = Zone.current;
  var _resultOrListeners;
@@ skipping 259 matching lines @@
      listenerHasValue = false;
      return;}
   }
  Function errorCallback = listener._onError;
  if (matchesTest && errorCallback != null) {
   try {
     if (errorCallback is ZoneBinaryCallback) {
       listenerValueOrError = zone.runBinary(errorCallback, asyncError.error, asyncError.stackTrace);
       }
      else {
-      listenerValueOrError = zone.runUnary(DEVC$RT.cast(errorCallback, Function, __t14, "CastGeneral", """line 515, column 54 of dart:async/future_impl.dart: """, errorCallback is __t14, false), asyncError.error);
+      listenerValueOrError = zone.runUnary(DEVC$RT.cast(errorCallback, Function, __t14, "CastGeneral", """line 515, column 54 of dart:async/future_impl.dart: """, errorCallback is __t14, true), asyncError.error);
       }
     }
    catch (e, s) {
     listenerValueOrError = identical(asyncError.error, e) ? asyncError : new AsyncError(e, s);
      listenerHasValue = false;
      return;}
    listenerHasValue = true;
   }
  else {
   listenerValueOrError = asyncError;
@@ skipping 116 matching lines @@
 }
 }
 );
  return result;
 }
 }
  typedef dynamic __t14(dynamic __u15);
  typedef bool __t16(dynamic __u17);
  typedef dynamic __t18();
  typedef dynamic __t20<T>(T __u21);