Add a `@JSExportName` annotation for internal use in the runtime (use it to export dart.assert inst…

lib/src/codegen/js_interop.dart

Index: lib/src/codegen/js_interop.dart
diff --git a/lib/src/codegen/js_interop.dart b/lib/src/codegen/js_interop.dart
index 1e6dff69bcbaa90cd632c7b5ae37d12a6e94c3ed..777a0097bde7e47720d2dd05638683a0c11c2baf 100644
--- a/lib/src/codegen/js_interop.dart
+++ b/lib/src/codegen/js_interop.dart
@@ -11,21 +11,40 @@ import 'package:analyzer/src/generated/constant.dart';
 bool _isJsLibType(String expectedName, Element e) =>
     e?.name == expectedName && _isJsLib(e.library);
 
+/// Returns true if [e] represents any library from `package:js` or is the
+/// internal `dart:_js_helper` library.
 bool _isJsLib(LibraryElement e) {
-  var libName = e?.name;
-  return libName == 'js' ||
-      libName == 'js.varargs' ||
-      libName == 'dart._js_helper';
+  if (e == null) return false;
+  var uri = e.source.uri;
+  if (uri.scheme == 'package' && uri.path.startsWith('js/')) return true;
+  if (uri.scheme == 'dart') {
+    return uri.path == '_js_helper' || uri.path == '_foreign_helper';
+  }
+  return false;
 }
 
+/// Whether [value] is a `@rest` annotation (to be used on function parameters
+/// to have them compiled as `...` rest params in ES6 outputs).
 bool isJsRestAnnotation(DartObjectImpl value) =>
     _isJsLibType('_Rest', value.type.element);
 
+/// Whether [i] is a `spread` invocation (to be used on function arguments
+/// to have them compiled as `...` spread args in ES6 outputs).
 bool isJsSpreadInvocation(MethodInvocation i) =>
     _isJsLibType('spread', i.methodName?.bestElement);
 
 // TODO(jmesserly): Move JsPeerInterface to package:js (see issue #135).
-bool isJSAnnotation(DartObjectImpl value) => value.type.name == 'JS';
+bool isJSAnnotation(DartObjectImpl value) =>
+    _isJsLibType('JS', value.type.element);
+
+/// Whether [value] is a `@JSExportName` (internal annotation used in SDK
+/// instead of `@JS` from `package:js`).
+bool isJSExportNameAnnotation(DartObjectImpl value) {
+  var e = value?.type?.element;
+  if (e?.name != 'JSExportName') return false;
+  var uri = e.source.uri;
+  return uri.scheme == 'dart' && uri.path == '_foreign_helper';
+}
 
 bool isJsPeerInterface(DartObjectImpl value) =>
     value.type.name == 'JsPeerInterface';