Implement type inference for await expressions in front_end.

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, 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 analyzer.test.src.task.strong.checker_test;
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'strong_test_helper.dart';
 
@@ skipping 904 matching lines @@
   test_functionModifiers_async() async {
     await checkFile('''
 import 'dart:async';
 import 'dart:math' show Random;
 
 dynamic x;
 
 foo1() async => x;
 Future foo2() async => x;
 Future<int> foo3() async => /*info:DYNAMIC_CAST*/x;
-Future<int> foo4() async => new Future<int>.value(x);
+Future<int> foo4() async => new Future<int>.value(/*info:DYNAMIC_CAST*/x);
 Future<int> foo5() async =>
-    /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(x);
+    /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(
+        /*info:DYNAMIC_CAST*/x);
 
 bar1() async { return x; }
 Future bar2() async { return x; }
 Future<int> bar3() async { return /*info:DYNAMIC_CAST*/x; }
-Future<int> bar4() async { return new Future<int>.value(x); }
+Future<int> bar4() async {
+  return new Future<int>.value(/*info:DYNAMIC_CAST*/x);
+}
 Future<int> bar5() async {
-  return /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(x);
+  return /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(
+      /*info:DYNAMIC_CAST*/x);
 }
 
 int y;
 Future<int> z;
 
 baz() async {
   int a = /*info:DYNAMIC_CAST*/await x;
   int b = await y;
   int c = await z;
   String d = /*error:INVALID_ASSIGNMENT*/await z;
@@ skipping 3258 matching lines @@
 class CheckerTest_Driver extends CheckerTest {
   @override
   bool get enableNewAnalysisDriver => true;
 
   @failingTest
   @override
   test_covariantOverride_fields() async {
     await super.test_covariantOverride_fields();
   }
 }