[dart2js] Use a Symbol to access JavaScript Array Rti

Use a JavaScript Symbol() for Array rti property. This makes the
property non-enumerable, avoiding making the property visible via
JS-interop.

The code is feature-tested so that IE11 still works with an enumerable
String property.

Bug: 40535
Change-Id: Ic8b64dac5751989fe4b8d023b0626c3db04676c6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/137245
Commit-Queue: Stephen Adams <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>

Author: rakudrama

pkg/compiler/lib/src/js_backend/namer.dart

@@ -266,7 +266,7 @@ class Namer extends ModularNamer {
 
     // 15.1.4 Constructor Properties of the Global Object
     "Object", "Function", "Array", "String", "Boolean", "Number", "Date",
-    "RegExp", "Error", "EvalError", "RangeError", "ReferenceError",
+    "RegExp", "Symbol", "Error", "EvalError", "RangeError", "ReferenceError",
     "SyntaxError", "TypeError", "URIError",
 
     // 15.1.5 Other Properties of the Global Object

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

@@ -1942,7 +1942,13 @@ class FragmentEmitter {
       globals.add(new js.Property(js.string(LEAF_TAGS), new js.LiteralNull()));
     }
 
-    js.ObjectInitializer globalsObject = new js.ObjectInitializer(globals);
+    globals.add(js.Property(
+        js.string(ARRAY_RTI_PROPERTY),
+        js.js(r'typeof Symbol == "function" && typeof Symbol() == "symbol"'
+            r'    ? Symbol("$ti")'
+            r'    : "$ti"')));
+
+    js.ObjectInitializer globalsObject = js.ObjectInitializer(globals);
 
     return js.js.statement('var init = #;', globalsObject);
   }

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart

@@ -9,6 +9,7 @@ import 'dart:math' show Random;
 
 import 'package:js_runtime/shared/embedded_names.dart'
     show
+        ARRAY_RTI_PROPERTY,
         DEFERRED_INITIALIZED,
         DEFERRED_LIBRARY_PARTS,
         DEFERRED_PART_URIS,

pkg/dev_compiler/tool/dart2js_nnbd_sdk_error_golden.txt

@@ -1,6 +1,6 @@
-ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|2688|17|17|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
-ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|3628|5|11|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
-ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|3656|5|6|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
+ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|2689|17|17|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
+ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|3629|5|11|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
+ERROR|COMPILE_TIME_ERROR|BODY_MIGHT_COMPLETE_NORMALLY|lib/_internal/js_runtime/lib/js_helper.dart|3657|5|6|The body might complete normally, which would cause 'null' to be returned, but the return type is a potentially non-nullable type.
 ERROR|COMPILE_TIME_ERROR|INCONSISTENT_INHERITANCE|lib/_internal/js_runtime/lib/interceptors.dart|1637|7|5|Superinterfaces don't have a valid override for '&': int.& (int Function(int)), JSNumber.& (num Function(num)).
 ERROR|COMPILE_TIME_ERROR|INCONSISTENT_INHERITANCE|lib/_internal/js_runtime/lib/interceptors.dart|1637|7|5|Superinterfaces don't have a valid override for '<<': int.<< (int Function(int)), JSNumber.<< (num Function(num)).
 ERROR|COMPILE_TIME_ERROR|INCONSISTENT_INHERITANCE|lib/_internal/js_runtime/lib/interceptors.dart|1637|7|5|Superinterfaces don't have a valid override for '>>': int.>> (int Function(int)), JSNumber.>> (num Function(num)).

sdk/lib/_internal/js_runtime/lib/js_helper.dart

@@ -8,6 +8,7 @@ library _js_helper;
 
 import 'dart:_js_embedded_names'
     show
+        ARRAY_RTI_PROPERTY,
         CURRENT_SCRIPT,
         DEFERRED_LIBRARY_PARTS,
         DEFERRED_PART_URIS,

sdk/lib/_internal/js_runtime/lib/js_rti.dart

@@ -98,12 +98,15 @@ getMangledTypeName(Type t) {
 Object setRuntimeTypeInfo(Object target, var rti) {
   if (JS_GET_FLAG('USE_NEW_RTI')) {
     assert(rti != null);
+    var rtiProperty = JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY);
+    JS('var', r'#[#] = #', target, rtiProperty, rti);
+    return target;
   } else {
     assert(rti == null || isJsArray(rti));
+    String rtiName = JS_GET_NAME(JsGetName.RTI_NAME);
+    JS('var', r'#[#] = #', target, rtiName, rti);
+    return target;
   }
-  String rtiName = JS_GET_NAME(JsGetName.RTI_NAME);
-  JS('var', r'#[#] = #', target, rtiName, rti);
-  return target;
 }
 
 /// Returns the runtime type information of [target]. The returned value is a

sdk/lib/_internal/js_runtime/lib/rti.dart

@@ -30,6 +30,7 @@ import 'dart:_js_embedded_names'
         JsBuiltin,
         JsGetName,
         RtiUniverseFieldNames,
+        ARRAY_RTI_PROPERTY,
         CONSTRUCTOR_RTI_CACHE_PROPERTY_NAME,
         RTI_UNIVERSE,
         TYPES;
@@ -685,7 +686,7 @@ Rti _arrayInstanceType(object) {
   // IE11 we would have to synthesise a String property-name with almost zero
   // chance of conflict.
 
-  var rti = JS('', r'#[#]', object, JS_GET_NAME(JsGetName.RTI_NAME));
+  var rti = JS('', r'#[#]', object, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY));
   var defaultRti = getJSArrayInteropRti();
 
   // Case 3.

sdk/lib/_internal/js_runtime/lib/shared/embedded_names.dart

@@ -123,6 +123,11 @@ const GET_ISOLATE_TAG = 'getIsolateTag';
 //    [INTERCEPTORS_BY_TAG] and [LEAF_TAGS].
 const ISOLATE_TAG = 'isolateTag';
 
+/// An embedded global that contains the property used to store type information
+/// on JavaScript Array instances. This is a Symbol (except for IE11, where is
+/// is a String).
+const ARRAY_RTI_PROPERTY = 'arrayRti';
+
 /// This embedded global (a function) returns the isolate-specific dispatch-tag
 /// that is used to accelerate interceptor calls.
 const DISPATCH_PROPERTY_NAME = "dispatchPropertyName";

sdk_nnbd/lib/_internal/js_runtime/lib/js_helper.dart

@@ -6,6 +6,7 @@ library _js_helper;
 
 import 'dart:_js_embedded_names'
     show
+        ARRAY_RTI_PROPERTY,
         CURRENT_SCRIPT,
         DEFERRED_LIBRARY_PARTS,
         DEFERRED_PART_URIS,

sdk_nnbd/lib/_internal/js_runtime/lib/js_rti.dart

@@ -96,12 +96,15 @@ getMangledTypeName(Type t) {
 Object setRuntimeTypeInfo(Object target, var rti) {
   if (JS_GET_FLAG('USE_NEW_RTI')) {
     assert(rti != null);
+    var rtiProperty = JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY);
+    JS('var', r'#[#] = #', target, rtiProperty, rti);
+    return target;
   } else {
     assert(rti == null || isJsArray(rti));
+    String rtiName = JS_GET_NAME(JsGetName.RTI_NAME);
+    JS('var', r'#[#] = #', target, rtiName, rti);
+    return target;
   }
-  String rtiName = JS_GET_NAME(JsGetName.RTI_NAME);
-  JS('var', r'#[#] = #', target, rtiName, rti);
-  return target;
 }
 
 /// Returns the runtime type information of [target]. The returned value is a