Add JSNative utility class with static methods methods to efficiently manipulate typed JSInterop ob…

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

 // Copyright (c) 2016, 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.
 
 library js_backend.native_data;
 
 import '../common.dart';
 import '../elements/elements.dart'
     show ClassElement, Element, FieldElement, FunctionElement, MemberElement;
 import '../native/behavior.dart' show NativeBehavior;
@@ skipping 17 matching lines @@
       <FunctionElement, NativeBehavior>{};
 
   /// Cache for [NativeBehavior]s for reading from native fields.
   Map<MemberElement, NativeBehavior> nativeFieldLoadBehavior =
       <FieldElement, NativeBehavior>{};
 
   /// Cache for [NativeBehavior]s for writing to native fields.
   Map<MemberElement, NativeBehavior> nativeFieldStoreBehavior =
       <FieldElement, NativeBehavior>{};
 
+  /// Prefix used to escape JS names that are not valid Dart names
+  /// when using JSInterop.
+  static const String _jsInteropEscapePrefix = r'JS$';
+
   /// Returns `true` if [element] is explicitly marked as part of JsInterop.
   bool _isJsInterop(Element element) {
     return jsInteropNames.containsKey(element.declaration);
   }
 
   /// Returns [element] as an explicit part of JsInterop. The js interop name is
   /// expected to be computed later.
   void markAsJsInterop(Element element) {
     jsInteropNames[element.declaration] = null;
   }
@@ skipping 38 matching lines @@
 
   String _jsNameHelper(Element element) {
     String jsInteropName = jsInteropNames[element.declaration];
     assert(invariant(element, !(_isJsInterop(element) && jsInteropName == null),
         message:
             'Element $element is js interop but js interop name has not yet '
             'been computed.'));
     if (jsInteropName != null && jsInteropName.isNotEmpty) {
       return jsInteropName;
     }
-    return element.isLibrary ? 'self' : element.name;
+    return element.isLibrary ? 'self' : getUnescapedJSInteropName(element.name);
   }
 
   /// Computes the name for [element] to use in the generated JavaScript. This
   /// is either given through a native annotation or a js interop annotation.
   String getFixedBackendName(Element element) {
     String name = nativeMemberName[element.declaration];
     if (name == null && isJsInterop(element)) {
       // If an element isJsInterop but _isJsInterop is false that means it is
       // considered interop as the parent class is interop.
       name = _jsNameHelper(
@@ skipping 102 matching lines @@
   /// Registers the [behavior] for reading from the native [field].
   void setNativeFieldLoadBehavior(FieldElement field, NativeBehavior behavior) {
     nativeFieldLoadBehavior[field] = behavior;
   }
 
   /// Registers the [behavior] for writing to the native [field].
   void setNativeFieldStoreBehavior(
       FieldElement field, NativeBehavior behavior) {
     nativeFieldStoreBehavior[field] = behavior;
   }
+
+  /// Apply JS$ escaping scheme to convert possible escaped Dart names into
+  /// JS names.
+  String getUnescapedJSInteropName(String name) {
+    return name.startsWith(_jsInteropEscapePrefix)
+        ? name.substring(_jsInteropEscapePrefix.length)
+        : name;
+  }
 }