[ddc] Change JSArray rti property into a getter

- Avoids the need to set the value in the JSArray factories.
- Delays the construction of the rti value until it is actually needed.

Issue: https://github.com/dart-lang/sdk/issues/48585
Change-Id: Iecc28533453742eaeedc0cbc48053b7660e3eee3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/325450
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>

pkg/dev_compiler/lib/src/kernel/compiler.dart

@@ -1757,6 +1757,11 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
         js_ast.Expression type;
         var memberName = _declareMemberName(member);
         if (member.isAccessor) {
+          // These signatures are used for dynamic access and to inform the
+          // debugger. The `arrayRti` accessor is only used by the dart:_rti
+          // library internals and should not be included in the accessible
+          // signatures.
+          if (c == _jsArrayClass && name == 'arrayRti') continue;
           type = _emitType(member.isGetter
               ? reifiedType.returnType
               : reifiedType.positionalParameters[0]);
@@ -6681,6 +6686,12 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
   js_ast.Expression _emitEmbeddedGlobal(StaticInvocation node) {
     var constantExpression = node.arguments.positional[1] as ConstantExpression;
     var name = constantExpression.constant as StringConstant;
+    var value = name.value;
+    if (value == 'arrayRti') {
+      // Special case for the rti on a JSArray. These are defined via the dartx
+      // extension functionality.
+      return _emitMemberName('arrayRti', memberClass: _jsArrayClass);
+    }
     return runtimeCall('#', [name.value]);
   }
 

sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/types.dart

@@ -106,9 +106,6 @@ void nativeNonNullAsserts(bool enable) {
   _nativeNonNullAsserts = enable;
 }
 
-/// A JavaScript Symbol used to store the Rti object on a native array.
-final arrayRti = JS('', r'Symbol("$ti")');
-
 /// A JavaScript Symbol used to store the Rti signature object on a function.
 ///
 /// Accessed by a call to `JS_GET_NAME(JsGetName.SIGNATURE_NAME)`.

sdk/lib/_internal/js_dev_runtime/private/js_array.dart

@@ -25,9 +25,6 @@ class JSArray<E> extends JavaScriptObject
     // TODO(jmesserly): this uses special compiler magic to close over the
     // parameterized ES6 'JSArray' class.
     jsObjectSetPrototypeOf(list, JS('', 'JSArray.prototype'));
-    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
-      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
-          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
@@ -35,9 +32,6 @@ class JSArray<E> extends JavaScriptObject
   factory JSArray.fixed(@notNull Object list) {
     jsObjectSetPrototypeOf(list, JS('', 'JSArray.prototype'));
     JS('', r'#.fixed$length = Array', list);
-    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
-      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
-          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
@@ -45,12 +39,27 @@ class JSArray<E> extends JavaScriptObject
     jsObjectSetPrototypeOf(list, JS('', 'JSArray.prototype'));
     JS('', r'#.fixed$length = Array', list);
     JS('', r'#.immutable$list = Array', list);
-    if (JS_GET_FLAG('NEW_RUNTIME_TYPES'))
-      JS('', '#.# = #', list, JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY),
-          JSArray<E>);
     return JS('-dynamic', '#', list);
   }
 
+  /// Provides the Rti object for this.
+  ///
+  /// Only intended for use by the dart:_rti library.
+  ///
+  /// NOTE: The name of this getter is directly tied to the result of compiling
+  /// `JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY)`.
+  Object get arrayRti => JS_GET_FLAG('NEW_RUNTIME_TYPES')
+      ? dart.typeRep<JSArray<E>>()
+      : throw dart.throwUnimplementedInOldRti();
+
+  /// Unsupported action, only provided here to help diagnosis of an accidental
+  /// attempt to set the value manually.
+  ///
+  /// NOTE: The name of this setter is directly tied to the result of compiling
+  /// `JS_EMBEDDED_GLOBAL('', ARRAY_RTI_PROPERTY)`.
+  set arrayRti(_) =>
+      throw UnsupportedError('Setting arrayRti is not supported in DDC.');
+
   static void markFixedList(list) {
     // Functions are stored in the hidden class and not as properties in
     // the object. We never actually look at the value, but only want