Perform type inference on explicitly typed fields.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, MemberKind, optional;
@@ skipping 348 matching lines @@
         } else {
           field = library[name];
         }
         if (field.next != null) {
           // TODO(ahe): This can happen, for example, if a final field is
           // combined with a setter.
           internalError(
               "Unhandled: '${field.name}' has more than one declaration.");
         }
         field.initializer = initializer;
+        _typeInferrer.inferFieldInitializer(field.builtType, initializer);
       }
     }
     pop(); // Type.
     pop(); // Modifiers.
   }
 
   @override
   void endMember() {
     debugEvent("Member");
     checkEmpty(-1);
@@ skipping 2799 matching lines @@
     if (starToken == null) {
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return internalError("Unknown async modifier: $asyncToken");
   }
 }