Change signature of lookupConstructor to only require a name.

pkg/compiler/lib/src/elements/modelx.dart

 // Copyright (c) 2013, 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 elements.modelx;
 
 import 'elements.dart';
 import '../constants/expressions.dart';
 import '../helpers/helpers.dart';  // Included for debug helpers.
 import '../tree/tree.dart';
@@ skipping 2175 matching lines @@
                                            Element noMatch(Element)) {
     if (result == null
         || !result.isConstructor
         || (isPrivateName(selector.name)
             && result.library != selector.library)) {
       result = noMatch != null ? noMatch(result) : null;
     }
     return result;
   }
 
-  // TODO(aprelev@gmail.com): Peter believes that it would be great to
-  // make noMatch a required argument. Peter's suspicion is that most
-  // callers of this method would benefit from using the noMatch method.
-  Element lookupConstructor(Selector selector, [Element noMatch(Element)]) {
-    Element result = localLookup(selector.name);
-    return validateConstructorLookupResults(selector, result, noMatch);
+  ConstructorElement lookupDefaultConstructor() {
+    ConstructorElement constructor = lookupConstructor("");
+    if (constructor != null
+        && constructor.functionSignature.requiredParameterCount == 0) {
+      return constructor;
+    }
+    return null;
+  }
+
+  ConstructorElement lookupConstructor(String name) {
+    Element result = localLookup(name);
+    return result != null && result.isConstructor ? result : null;
   }
 
   Link<Element> get constructors {
     // TODO(ajohnsen): See if we can avoid this method at some point.
     Link<Element> result = const Link<Element>();
     // TODO(johnniwinther): Should we include injected constructors?
     forEachMember((_, Element member) {
       if (member.isConstructor) result = result.prepend(member);
     });
     return result;
@@ skipping 613 matching lines @@
   AstElement get definingElement;
 
   bool get hasResolvedAst => definingElement.hasTreeElements;
 
   ResolvedAst get resolvedAst {
     return new ResolvedAst(declaration,
         definingElement.node, definingElement.treeElements);
   }
 
 }