Fix hints reported by analyzer.

pkg/compiler/lib/src/ssa/kernel_ast_adapter.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.
 
 import 'package:js_runtime/shared/embedded_names.dart';
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../compiler.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
 import '../elements/resolution_types.dart';
 import '../elements/elements.dart';
 import '../elements/modelx.dart';
 import '../js/js.dart' as js;
 import '../js_backend/backend_helpers.dart';
 import '../js_backend/js_backend.dart';
 import '../kernel/kernel.dart';
 import '../kernel/kernel_debug.dart';
 import '../native/native.dart' as native;
 import '../resolution/tree_elements.dart';
 import '../tree/tree.dart' as ast;
 import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
 import '../universe/side_effects.dart';
 import '../world.dart';
-import 'jump_handler.dart' show SwitchCaseJumpHandler;
 import 'locals_handler.dart';
 import 'types.dart';
 
 /// A helper class that abstracts all accesses of the AST from Kernel nodes.
 ///
 /// The goal is to remove all need for the AST from the Kernel SSA builder.
 class KernelAstAdapter {
   final Kernel kernel;
   final JavaScriptBackend _backend;
   final Map<ir.Node, ast.Node> _nodeToAst;
@@ skipping 908 matching lines @@
         new CallStructure(
             node.arguments.positional.length + argumentNames.length,
             argumentNames),
         arguments);
   }
 
   @override
   ConstantExpression visitStaticGet(ir.StaticGet node) {
     Element element = astAdapter.getMember(node.target);
     if (element.isField) {
-      return new VariableConstantExpression(element);
+      return new VariableConstantExpression(element as MemberElement);
     }
     astAdapter.reporter.internalError(
         CURRENT_ELEMENT_SPANNABLE, "Unexpected constant target: $element.");
     return null;
   }
 
   @override
   ConstantExpression visitStringLiteral(ir.StringLiteral node) {
     return new StringConstantExpression(node.value);
   }
@@ skipping 56 matching lines @@
   String get name => null;
 
   @override
   int get nestingLevel => 1;
 
   @override
   ast.Node get statement => null;
 
   String toString() => 'Target:$targetStatement';
 }