Handle explicit constructor.

pkg/compiler/lib/src/resolution/constructors.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.resolution.constructors;
 
 import '../common.dart';
 import '../common/resolution.dart' show Feature;
 import '../compiler.dart' show Compiler;
 import '../constants/constructors.dart'
@@ skipping 231 matching lines @@
         kind, arguments, name, visitor.currentClass);
   }
 
   /// Checks that [lookedupConstructor] is valid as a target for the super/this
   /// constructor call using with the given [callStructure].
   ///
   /// If [lookedupConstructor] is valid it is returned, otherwise an error is
   /// reported and an [ErroneousConstructorElement] is returned.
   ConstructorElement verifyThatConstructorMatchesCall(
       Node node,
-      ConstructorElementX lookedupConstructor,
+      ConstructorElement lookedupConstructor,

[Siggi Cherem (dart-lang), 2016/05/17 20:42:38]

funny that all of the semantic changes are just 1 char :)

[Johnni Winther, 2016/05/18 10:17:21]

Yes :)

       CallStructure callStructure,
       String className,
       {String constructorName: '',
       bool isImplicitSuperCall: false,
       bool isThisCall: false}) {
     Element result = lookedupConstructor;
     if (lookedupConstructor == null) {
       String fullConstructorName =
           Elements.constructorNameForDiagnostics(className, constructorName);
       MessageKind kind = isImplicitSuperCall
@@ skipping 586 matching lines @@
     // constructors.
     return null;
   }
   // TODO(johnniwinther): Use [Name] for lookup.
   ConstructorElement constructor = cls.lookupConstructor(constructorName);
   if (constructor != null) {
     constructor = constructor.declaration;
   }
   return constructor;
 }