Fix inference of the static type of an async function literal.

pkg/analyzer/test/generated/non_error_resolver_test.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 engine.non_error_resolver_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
@@ skipping 321 matching lines @@
 typedef Future<int> F(int i);
 main() {
   F f = (int i) async => i;
 }
 ''');
     resolve(source);
     assertNoErrors(source);
     verify([source]);
   }
 
+  void test_async_flattened() {
+    Source source = addSource('''
+import 'dart:async';
+typedef Future<int> CreatesFutureInt();
+main() {
+  CreatesFutureInt createFutureInt = () async => f();
+  Future<int> futureInt = createFutureInt();
+  futureInt.then((int i) => print(i));
+}
+Future<int> f() => null;
+''');
+    resolve(source);
+    assertNoErrors(source);
+    verify([source]);
+  }
+
   void test_async_future_dynamic_with_return() {
     Source source = addSource('''
 import 'dart:async';
 Future<dynamic> f() async {
   return;
 }
 ''');
     resolve(source);
     assertNoErrors(source);
     verify([source]);
@@ skipping 4988 matching lines @@
     resolve(source);
     assertNoErrors(source);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "a");
   }
 }