dart2js: Introduce HGetLength to replace strange use of HFieldGet

pkg/compiler/lib/src/ssa/codegen.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.
 
 import 'dart:math' as math;
 import '../common.dart';
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
@@ skipping 1918 matching lines @@
           backend.namer.aliasedSuperMemberPropertyName(superElement),
           visitArguments(node.inputs, start: 1)
         ]) // Skip receiver argument.
             .withSourceInformation(node.sourceInformation));
       }
     }
   }
 
   visitFieldGet(HFieldGet node) {
     use(node.receiver);
-    MemberEntity element = node.element;
     if (node.isNullCheck) {
       // We access a JavaScript member we know all objects besides
       // null and undefined have: V8 does not like accessing a member
       // that does not exist.
       push(new js.PropertyAccess.field(pop(), 'toString')
           .withSourceInformation(node.sourceInformation));
-    } else if (element == helpers.jsIndexableLength) {
-      // We're accessing a native JavaScript property called 'length'
-      // on a JS String or a JS array. Therefore, the name of that
-      // property should not be mangled.
-      push(new js.PropertyAccess.field(pop(), 'length')
-          .withSourceInformation(node.sourceInformation));
     } else {
-      FieldEntity field = element;
+      FieldEntity field = node.element;
       js.Name name = backend.namer.instanceFieldPropertyName(field);
       push(new js.PropertyAccess(pop(), name)
           .withSourceInformation(node.sourceInformation));
       registry.registerStaticUse(new StaticUse.fieldGet(field));
     }
   }
 
   visitFieldSet(HFieldSet node) {
-    MemberEntity element = node.element;
+    FieldEntity element = node.element;
     registry.registerStaticUse(new StaticUse.fieldSet(element));
     js.Name name = backend.namer.instanceFieldPropertyName(element);
     use(node.receiver);
     js.Expression receiver = pop();
     use(node.value);
     push(new js.Assignment(new js.PropertyAccess(receiver, name), pop())
         .withSourceInformation(node.sourceInformation));
   }
 
+  visitGetLength(HGetLength node) {
+    use(node.receiver);
+    push(new js.PropertyAccess.field(pop(), 'length')
+        .withSourceInformation(node.sourceInformation));
+  }
+
   visitReadModifyWrite(HReadModifyWrite node) {
     FieldEntity element = node.element;
     registry.registerStaticUse(new StaticUse.fieldGet(element));
     registry.registerStaticUse(new StaticUse.fieldSet(element));
     js.Name name = backend.namer.instanceFieldPropertyName(element);
     use(node.receiver);
     js.Expression fieldReference = new js.PropertyAccess(pop(), name);
     if (node.isPreOp) {
       push(new js.Prefix(node.jsOp, fieldReference)
           .withSourceInformation(node.sourceInformation));
@@ skipping 1133 matching lines @@
     registry.registerStaticUse(new StaticUse.staticInvoke(
         helper, new CallStructure.unnamed(argumentCount)));
     return backend.emitter.staticFunctionAccess(helper);
   }
 
   @override
   void visitRef(HRef node) {
     visit(node.value);
   }
 }