Tag default constructors in rasta

pkg/compiler/lib/src/kernel/kernel.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.md file.
 
 import 'dart:collection' show Queue;
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/verifier.dart' show CheckParentPointers;
 
 import '../common.dart';
@@ skipping 413 matching lines @@
     return functions.putIfAbsent(function, () {
       assert(compiler.resolution.hasBeenResolved(function) ||
           function.isMalformed);
       function = function.implementation;
       ir.Member member;
       ir.Constructor constructor;
       ir.Procedure procedure;
       ir.Name name = irName(function.name, function);
       bool isNative = isNativeMethod(function);
       if (function.isGenerativeConstructor) {
+        ConstructorElement constructorElement = function;
         member = constructor = new ir.Constructor(null,
             name: name,
-            isConst: function.isConst,
-            isExternal: isNative || function.isExternal,
-            initializers: null);
+            isConst: constructorElement.isConst,
+            isExternal: isNative || constructorElement.isExternal,
+            initializers: null,
+            isSyntheticDefault: constructorElement.isDefaultConstructor);
       } else {
         member = procedure = new ir.Procedure(name, null, null,
             isAbstract: function.isAbstract,
             isStatic: function.isStatic ||
                 function.isTopLevel ||
                 function.isFactoryConstructor,
             isExternal: isNative || function.isExternal,
             isConst: false); // TODO(ahe): When is this true?
       }
       addWork(function, () {
@@ skipping 337 matching lines @@
 }
 
 class ConstructorTarget {
   final ConstructorElement element;
   final ResolutionDartType type;
 
   ConstructorTarget(this.element, this.type);
 
   String toString() => "ConstructorTarget($element, $type)";
 }