Support serialization of all resolved asts from dart:core

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

 // Copyright (c) 2015, 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 dart2js.js_backend.helpers;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Uris;
 import '../common/resolution.dart' show Resolution;
 import '../compiler.dart' show Compiler;
 import '../core_types.dart' show CoreClasses;
 import '../elements/elements.dart'
     show
         AbstractFieldElement,
         ClassElement,
         ConstructorElement,
         Element,
         EnumClassElement,
         FunctionElement,
         LibraryElement,
-        MethodElement;
+        MethodElement,
+        PublicName;
 import '../library_loader.dart' show LoadedLibraries;
+import '../universe/call_structure.dart' show CallStructure;
+import '../universe/selector.dart' show Selector;
 
 import 'js_backend.dart';
 
 /// Helper classes and functions for the JavaScript backend.
 class BackendHelpers {
   static final Uri DART_JS_HELPER = new Uri(scheme: 'dart', path: '_js_helper');
   static final Uri DART_INTERCEPTORS =
       new Uri(scheme: 'dart', path: '_interceptors');
   static final Uri DART_FOREIGN_HELPER =
       new Uri(scheme: 'dart', path: '_foreign_helper');
@@ skipping 134 matching lines @@
 
   /// Holds the method "requiresPreamble" in _js_helper.
   FunctionElement requiresPreambleMarker;
 
   /// Holds the class for the [JsGetName] enum.
   EnumClassElement jsGetNameEnum;
 
   /// Holds the class for the [JsBuiltins] enum.
   EnumClassElement jsBuiltinEnum;
 
+  ClassElement _symbolImplementationClass;
+  ClassElement get symbolImplementationClass {

[Siggi Cherem (dart-lang), 2016/04/14 15:38:20]

nit - rewrite as:

ClassElement get symbolImplementationClass =>
    _symbolImplementationClass ??= find(internalLibrary, 'Symbol');

[Johnni Winther, 2016/04/15 07:27:42]

Done.

+    if (_symbolImplementationClass == null) {
+      _symbolImplementationClass = find(internalLibrary, 'Symbol');
+    }
+    return _symbolImplementationClass;
+  }
+
+  final Selector symbolValidatedConstructorSelector =
+      new Selector.call(const PublicName('validated'), CallStructure.ONE_ARG);
+
+  ConstructorElement _symbolValidatedConstructor;
+  ConstructorElement get symbolValidatedConstructor {
+    if (_symbolValidatedConstructor == null) {
+      String name = symbolValidatedConstructorSelector.name;

[Siggi Cherem (dart-lang), 2016/04/14 15:38:20]

Maybe introduce a helper method for these lookups?  (I'm guessing this pattern
to lookup a constructor/member is going to come up several times and is similar
to the one in compiler.dart already.). For example:

ConstructorElement get symbolValidatedConstructor =>
    _symbolValidatedConstructor ??= findConstructor(symbolImplementationClass,
'validated')

[Johnni Winther, 2016/04/15 07:27:42]

Done.

+      symbolImplementationClass.ensureResolved(resolution);
+      _symbolValidatedConstructor =
+          symbolImplementationClass.lookupConstructor(name);
+      assert(invariant(
+          symbolImplementationClass, _symbolValidatedConstructor != null,
+          message: "Constructor '$name' not found in "
+              "'${symbolImplementationClass}'."));
+    }
+    return _symbolValidatedConstructor;
+  }
+
   // TODO(johnniwinther): Make these private.
   // TODO(johnniwinther): Split into findHelperFunction and findHelperClass and
   // add a check that the element has the expected kind.
   Element findHelper(String name) => find(jsHelperLibrary, name);
   Element findAsyncHelper(String name) => find(asyncLibrary, name);
   Element findInterceptor(String name) => find(interceptorsLibrary, name);
   Element find(LibraryElement library, String name) {
     Element element = library.implementation.findLocal(name);
     assert(invariant(library, element != null,
         message: "Element '$name' not found in '${library.canonicalUri}'."));
@@ skipping 486 matching lines @@
   MethodElement _objectNoSuchMethod;
 
   MethodElement get objectNoSuchMethod {
     if (_objectNoSuchMethod == null) {
       _objectNoSuchMethod =
           coreClasses.objectClass.lookupLocalMember(Identifiers.noSuchMethod_);
     }
     return _objectNoSuchMethod;
   }
 }