Avoid generating VariableUse nodes with non-identifier names

sdk/lib/_internal/compiler/implementation/js_backend/checked_mode_helpers.dart

 // Copyright (c) 2013, 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.
 
 part of js_backend;
 
 class CheckedModeHelper {
   final String name;
 
   const CheckedModeHelper(String this.name);
 
   Element getElement(Compiler compiler) => compiler.findHelper(name);
 
   jsAst.Expression generateCall(SsaCodeGenerator codegen,
                                 HTypeConversion node) {
     Element helperElement = getElement(codegen.compiler);
     codegen.world.registerStaticUse(helperElement);
     List<jsAst.Expression> arguments = <jsAst.Expression>[];
     codegen.use(node.checkedInput);
     arguments.add(codegen.pop());
     generateAdditionalArguments(codegen, node, arguments);
-    String helperName = codegen.backend.namer.isolateAccess(helperElement);
-    return new jsAst.Call(new jsAst.VariableUse(helperName), arguments);
+    jsAst.Expression helper = codegen.backend.namer.elementAccess(helperElement);
+    return new jsAst.Call(helper, arguments);
   }
 
   void generateAdditionalArguments(SsaCodeGenerator codegen,
                                    HTypeConversion node,
                                    List<jsAst.Expression> arguments) {
     // No additional arguments needed.
   }
 
   static const List<CheckedModeHelper> helpers = const <CheckedModeHelper> [
       const MalformedCheckedModeHelper('checkMalformedType'),
@@ skipping 76 matching lines @@
     DartType type = node.typeExpression;
     Element element = type.element;
     String isField = codegen.backend.namer.operatorIs(element);
     arguments.add(js.string(isField));
     codegen.use(node.typeRepresentation);
     arguments.add(codegen.pop());
     String asField = codegen.backend.namer.substitutionName(element);
     arguments.add(js.string(asField));
   }
 }