Fix hints reported by analyzer.

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index f1396caa299e16ae728946d691b1ed38ce6dca30..715b66ab57f99d332ed5e3176d341810c34f4ab1 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -27,7 +27,6 @@ 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';
 
@@ -956,7 +955,7 @@ class Constantifier extends ir.ExpressionVisitor<ConstantExpression> {
   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.");