// Copyright (c) 2011, 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.diagnostics.spannable;

/**
 * Tagging interface for classes from which source spans can be generated.
 */
// TODO(johnniwinther): Find a better name.
// TODO(ahe): How about "Bolt"?
abstract class Spannable {}

class _SpannableSentinel implements Spannable {
  final String name;

  const _SpannableSentinel(this.name);

  String toString() => name;
}

/// Sentinel spannable used to mark that diagnostics should point to the
/// current element. Note that the diagnostic reporting will fail if the current
/// element is `null`.
const Spannable CURRENT_ELEMENT_SPANNABLE =
    const _SpannableSentinel("Current element");

/// Sentinel spannable used to mark that there might be no location for the
/// diagnostic. Use this only when it is not an error not to have a current
/// element.
const Spannable NO_LOCATION_SPANNABLE = const _SpannableSentinel("No location");

class SpannableAssertionFailure {
  final Spannable node;
  final String message;
  SpannableAssertionFailure(this.node, this.message);

  String toString() => 'Assertion failure'
      '${message != null ? ': $message' : ''}';
}