Infer the return types of local functions where appropriate.

pkg/front_end/testcases/inference/infer_local_function_return_type.dart

 // Copyright (c) 2017, 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.
 
 /*@testedFeatures=inference*/
 library test;
 
 test() {
-  f0() => 42;
-  f1() async => 42;
+  /*@returnType=int*/ f0() => 42;
+  /*@returnType=Future<int>*/ f1() async => 42;
 
-  f2() {
+  /*@returnType=int*/ f2() {
     return 42;
   }
 
-  f3() async {
+  /*@returnType=Future<int>*/ f3() async {
     return 42;
   }
 
-  f4() sync* {
+  /*@returnType=Iterable<int>*/ f4() sync* {
     yield 42;
   }
 
-  f5() async* {
+  /*@returnType=Stream<int>*/ f5() async* {
     yield 42;
   }
 
   num f6() => 42;
 
-  f7() => f7();
-  f8() => /*error:REFERENCED_BEFORE_DECLARATION*/ f9();
-  f9() => f5();
+  /*@returnType=dynamic*/ f7() => f7();
+  /*@returnType=Stream<int>*/ f8() => f5();
 
   var /*@type=() -> int*/ v0 = f0;
   var /*@type=() -> Future<int>*/ v1 = f1;
   var /*@type=() -> int*/ v2 = f2;
   var /*@type=() -> Future<int>*/ v3 = f3;
   var /*@type=() -> Iterable<int>*/ v4 = f4;
   var /*@type=() -> Stream<int>*/ v5 = f5;
   var /*@type=() -> num*/ v6 = f6;
   var /*@type=() -> dynamic*/ v7 = f7;
-  var /*@type=() -> dynamic*/ v8 = f8;
-  var /*@type=() -> Stream<int>*/ v9 = f9;
+  var /*@type=() -> Stream<int>*/ v8 = f8;
 }
 
 main() {}