Prepare for separate setter scope.

pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.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 file.
 
 library fasta.constructor_reference_builder;
 
 import 'builder.dart'
     show Builder, ClassBuilder, PrefixBuilder, Scope, TypeBuilder;
 
 import '../messages.dart' show warning;
@@ skipping 18 matching lines @@
     int index = name.indexOf(".");
     Builder builder;
     if (index == -1) {
       builder = scope.lookup(name, charOffset, fileUri);
     } else {
       String prefix = name.substring(0, index);
       String middle = name.substring(index + 1);
       builder = scope.lookup(prefix, charOffset, fileUri);
       if (builder is PrefixBuilder) {
         PrefixBuilder prefix = builder;
-        builder = prefix.exports[middle];
+        builder = prefix.lookup(middle, charOffset, fileUri);
       } else if (builder is ClassBuilder) {
         ClassBuilder cls = builder;
-        builder = cls.constructors[middle];
+        builder = cls.findConstructorOrFactory(middle, charOffset, fileUri);
         if (suffix == null) {
           target = builder;
           return;
         }
       }
     }
     if (builder is ClassBuilder) {
-      target = builder.constructors[suffix ?? ""];
+      target =
+          builder.findConstructorOrFactory(suffix ?? "", charOffset, fileUri);
     }
     if (target == null) {
-      warning(null, -1, "Couldn't find constructor '$fullNameForErrors'.");
+      warning(fileUri, charOffset,
+          "Couldn't find constructor '$fullNameForErrors'.");
     }
   }
 }