Expand ResolvedAst to handle synthetic constructors.

tests/compiler/dart2js/related_types.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 related_types;
 
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/core_types.dart';
 import 'package:compiler/src/dart_types.dart';
@@ skipping 41 matching lines @@
       checkMemberElement(compiler, element);
     }
   });
 }
 
 /// Check [member] for unrelated types.
 void checkMemberElement(Compiler compiler, MemberElement member) {
   if (!compiler.resolution.hasBeenResolved(member)) return;
 
   ResolvedAst resolvedAst = member.resolvedAst;
-  RelatedTypesChecker relatedTypesChecker =
-      new RelatedTypesChecker(compiler, resolvedAst);
-  if (resolvedAst.node != null) {
+  if (resolvedAst.kind == ResolvedAstKind.PARSED) {
+    RelatedTypesChecker relatedTypesChecker =
+        new RelatedTypesChecker(compiler, resolvedAst);
     compiler.reporter.withCurrentElement(member.implementation, () {
       relatedTypesChecker.apply(resolvedAst.node);
     });
   }
 }
 
 class RelatedTypesChecker extends TraversalVisitor<DartType, dynamic> {
   final Compiler compiler;
   final ResolvedAst resolvedAst;
 
@@ skipping 354 matching lines @@
   ClassElement findClass(DartType type) => type.accept(this, null);
 
   @override
   ClassElement visitType(DartType type, _) => null;
 
   @override
   ClassElement visitInterfaceType(InterfaceType type, _) {
     return type.element;
   }
 }