[ddc] Fix method call on object without prototype

Creating a js object with `Object.create(null)` produces an empty
js object with no prototype. Calling methods attached to these
objects would result in a NPE since we assumed all objects would
have a valid `.__proto__`.

Discovered the error in some benchmark code. Created a new test
with the same patterns.

Change-Id: I1fd38893b0c90315b338c3b6a1b4981be1d64065
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156582
Commit-Queue: Nicholas Shahan <nshahan@google.com>
Reviewed-by: Mark Zhou <markzipan@google.com>

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

@@ -268,9 +268,18 @@ getStaticSetters(value) => _getMembers(value, _staticSetterSig);
 
 getGenericTypeCtor(value) => JS('', '#[#]', value, _genericTypeCtor);
 
-/// Get the type of a method from an object using the stored signature
-getType(obj) =>
-    JS('', '# == null ? # : #.__proto__.constructor', obj, Object, obj);
+/// Get the type of an object.
+getType(obj) {
+  if (obj == null) return JS('!', '#', Object);
+
+  if (JS<bool>('!', '#.__proto__ == null', obj)) {
+    // Object.create(null) produces a js object without a prototype.
+    // In that case use the version from a js object literal.
+    return JS('!', '#.Object.prototype.constructor', global_);
+  }
+
+  return JS('!', '#.__proto__.constructor', obj);
+}
 
 getLibraryUri(value) => JS('', '#[#]', value, _libraryUri);
 setLibraryUri(f, uri) => JS('', '#[#] = #', f, _libraryUri, uri);

tests/lib/js/method_call_on_object_test.dart

@@ -0,0 +1,65 @@
+// Copyright (c) 2020, 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.
+
+// Tests method calls (typed and dynamic) on various forms of JS objects.
+
+@JS()
+library js_parameters_test;
+
+import 'package:js/js.dart';
+import 'package:expect/expect.dart';
+
+@JS()
+external void eval(String code);
+
+@JS()
+class Foo {
+  external Foo();
+  external dynamic method(int x);
+}
+
+@JS()
+external Foo makeFooLiteral();
+
+@JS()
+external Foo makeFooObjectCreate();
+
+main() {
+  // These examples from based on benchmarks-internal/js
+  eval(r'''
+self.Foo = function Foo() {}
+self.Foo.prototype.method = function(x) { return x + 1; }
+
+self.makeFooLiteral = function() {
+  return {
+    method: function(x) { return x + 1; }
+  }
+}
+
+// Objects created in this way have no prototype.
+self.makeFooObjectCreate = function() {
+  var o = Object.create(null);
+  o.method = function(x) { return x + 1; }
+  return o;
+}
+''');
+
+  var foo = Foo();
+  Expect.equals(2, foo.method(1));
+
+  foo = makeFooLiteral();
+  Expect.equals(2, foo.method(1));
+
+  foo = makeFooObjectCreate();
+  Expect.equals(2, foo.method(1));
+
+  dynamic dynamicFoo = Foo();
+  Expect.equals(2, dynamicFoo.method(1));
+
+  dynamicFoo = makeFooLiteral();
+  Expect.equals(2, dynamicFoo.method(1));
+
+  dynamicFoo = makeFooObjectCreate();
+  Expect.equals(2, dynamicFoo.method(1));
+}

tests/lib_2/js/method_call_on_object_test.dart

@@ -0,0 +1,65 @@
+// Copyright (c) 2020, 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.
+
+// Tests method calls (typed and dynamic) on various forms of JS objects.
+
+@JS()
+library js_parameters_test;
+
+import 'package:js/js.dart';
+import 'package:expect/expect.dart';
+
+@JS()
+external void eval(String code);
+
+@JS()
+class Foo {
+  external Foo();
+  external dynamic method(int x);
+}
+
+@JS()
+external Foo makeFooLiteral();
+
+@JS()
+external Foo makeFooObjectCreate();
+
+main() {
+  // These examples from based on benchmarks-internal/js
+  eval(r'''
+self.Foo = function Foo() {}
+self.Foo.prototype.method = function(x) { return x + 1; }
+
+self.makeFooLiteral = function() {
+  return {
+    method: function(x) { return x + 1; }
+  }
+}
+
+// Objects created in this way have no prototype.
+self.makeFooObjectCreate = function() {
+  var o = Object.create(null);
+  o.method = function(x) { return x + 1; }
+  return o;
+}
+''');
+
+  var foo = Foo();
+  Expect.equals(2, foo.method(1));
+
+  foo = makeFooLiteral();
+  Expect.equals(2, foo.method(1));
+
+  foo = makeFooObjectCreate();
+  Expect.equals(2, foo.method(1));
+
+  dynamic dynamicFoo = Foo();
+  Expect.equals(2, dynamicFoo.method(1));
+
+  dynamicFoo = makeFooLiteral();
+  Expect.equals(2, dynamicFoo.method(1));
+
+  dynamicFoo = makeFooObjectCreate();
+  Expect.equals(2, dynamicFoo.method(1));
+}