Infer the return types of local functions where appropriate.

pkg/front_end/testcases/inference/parameter_defaults_upwards.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;
 
 class C<T> {
   C.optional(void func([T x])) {}
   C.named(void func({T x})) {}
 }
 
 void optional_toplevel([x = /*@typeArgs=int*/ const [0]]) {}
 
 void named_toplevel({x: /*@typeArgs=int*/ const [0]}) {}
 
 main() {
-  void optional_local([x = /*@typeArgs=int*/ const [0]]) {}
-  void named_local({x: /*@typeArgs=int*/ const [0]}) {}
+  void optional_local([/*@type=dynamic*/ x = /*@typeArgs=int*/ const [0]]) {}
+  void named_local({/*@type=dynamic*/ x: /*@typeArgs=int*/ const [0]}) {}
   var /*@type=C<dynamic>*/ c_optional_toplevel =
       new /*@typeArgs=dynamic*/ C.optional(optional_toplevel);
   var /*@type=C<dynamic>*/ c_named_toplevel =
       new /*@typeArgs=dynamic*/ C.named(named_toplevel);
   var /*@type=C<dynamic>*/ c_optional_local =
       new /*@typeArgs=dynamic*/ C.optional(optional_local);
   var /*@type=C<dynamic>*/ c_named_local =
       new /*@typeArgs=dynamic*/ C.named(named_local);
   var /*@type=C<dynamic>*/ c_optional_closure =
       new /*@typeArgs=dynamic*/ C.optional(/*@returnType=Null*/ (
           [/*@type=dynamic*/ x = /*@typeArgs=int*/ const [0]]) {});
   var /*@type=C<dynamic>*/ c_named_closure = new /*@typeArgs=dynamic*/ C.named(
       /*@returnType=Null*/ (
           {/*@type=dynamic*/ x: /*@typeArgs=int*/ const [0]}) {});
 }