Implement line and column numbers.

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
     PrefixBuilder,
     ClassBuilder,
     Builder,
     TypeBuilder;
 
+import '../messages.dart' show
+    warning;
+
 import 'scope.dart' show
     Scope;
 
 class ConstructorReferenceBuilder extends Builder {
   final String name;
 
   final List<TypeBuilder> typeArguments;
 
   /// This is the name of a named constructor. As `bar` in `new Foo<T>.bar()`.
   final String suffix;
@@ skipping 24 matching lines @@
         if (suffix == null) {
           target = builder;
           return;
         }
       }
     }
     if (builder is ClassBuilder) {
       target = builder.constructors[suffix ?? ""];
     }
     if (target == null) {
-      print("Couldn't find constructor $fullNameForErrors.");
+      warning(null, -1, "Couldn't find constructor '$fullNameForErrors'.");
     }
   }
 }