Handle signature types and fields in kernel_impact

pkg/compiler/lib/src/elements/elements.dart

 // Copyright (c) 2012, 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 elements;
 
 import '../common.dart';
 import '../common/resolution.dart' show Resolution;
 import '../compiler.dart' show Compiler;
 import '../constants/constructors.dart';
@@ skipping 1157 matching lines @@
  * looking at code like "foo.x", we don't have to look for both a
  * field named "x", a getter named "x", and a setter named "x=".
  */
 abstract class AbstractFieldElement extends Element {
   GetterElement get getter;
   SetterElement get setter;
 }
 
 abstract class FunctionSignature {
   FunctionType get type;
+  DartType get returnType;
   List<DartType> get typeVariables;
   List<FormalElement> get requiredParameters;
   List<FormalElement> get optionalParameters;
 
   int get requiredParameterCount;
   int get optionalParameterCount;
   bool get optionalParametersAreNamed;
   bool get hasOptionalParameters;
 
   int get parameterCount;
@@ skipping 720 matching lines @@
   /// by a field.
   bool get isDeclaredByField;
 
   /// Returns `true` if this member is abstract.
   bool get isAbstract;
 
   /// If abstract, [implementation] points to the overridden concrete member,
   /// if any. Otherwise [implementation] points to the member itself.
   Member get implementation;
 }