Implement line and column numbers.

pkg/front_end/lib/src/fasta/builder/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.builder;
 
 import '../errors.dart' show
     internalError;
 
+import '../messages.dart' show
+    nit;
+
 export 'class_builder.dart' show
     ClassBuilder;
 
 export 'field_builder.dart' show
     FieldBuilder;
 
 export 'library_builder.dart' show
     LibraryBuilder;
 
 export 'procedure_builder.dart' show
@@ skipping 100 matching lines @@
       hidden = other;
     } else if (getUri(other)?.scheme == "dart" &&
         getUri(this)?.scheme != "dart") {
       preferred = this;
       hidden = other;
     } else if (getUri(this)?.scheme == "dart" &&
         getUri(other)?.scheme != "dart") {
       preferred = other;
       hidden = this;
     } else {
-      print("${library.uri}: Note: '$name' is imported from both "
+      nit(library.fileUri, -1, "'$name' is imported from both "

[karlklose, 2017/02/20 08:06:19]

Consider defining a constant (like NO_COLUMN_INFORMATION) for -1 and use it
instead.

[ahe, 2017/02/20 08:47:02]

Normally, I do prefer naming constants, but it feels like -1 is so universally
recognized that it wouldn't add much value. Do you have any strong preferences
on this?

           "'${getUri(this)}' and '${getUri(other)}'.");
       return library.buildAmbiguousBuilder(name, this, other, charOffset);
     }
     if (isLocal) {
-      print("${library.uri}: Note: local definition of '$name' hides imported "
+      nit(library.fileUri, -1, "Local definition of '$name' hides imported "
           "version from '${getUri(other)}'.");
     } else {
-      print("${library.uri}: import of '$name' (from '${getUri(preferred)}') "
-          "hides imported version from '${getUri(hidden)}'.");
+      nit(library.fileUri, -1, "Import of '$name' "
+          "(from '${getUri(preferred)}') hides imported version from "
+          "'${getUri(hidden)}'.");
     }
     return preferred;
   }
 
   Builder get parent => null;
 
   bool get isFinal => false;
 
   bool get isField => false;
 
@@ skipping 23 matching lines @@
 
   static Uri getUri(Builder builder) {
     if (builder == null) return internalError("Builder is null.");
     while (builder != null) {
       if (builder is LibraryBuilder) return builder.uri;
       builder = builder.parent;
     }
     return internalError("No library parent.");
   }
 }