Roll Observatory packages and add a roll script

source_span/lib/src/span.dart

-// Copyright (c) 2014, 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 source_span.span;
-
-import 'location.dart';
-import 'span_mixin.dart';
-
-/// A class that describes a segment of source text.
-abstract class SourceSpan implements Comparable<SourceSpan> {
-  /// The start location of this span.
-  final SourceLocation start;
-
-  /// The end location of this span, exclusive.
-  final SourceLocation end;
-
-  /// The source text for this span.
-  final String text;
-
-  /// The URL of the source (typically a file) of this span.
-  ///
-  /// This may be null, indicating that the source URL is unknown or
-  /// unavailable.
-  final Uri sourceUrl;
-
-  /// The length of this span, in characters.
-  final int length;
-
-  /// Creates a new span from [start] to [end] (exclusive) containing [text].
-  ///
-  /// [start] and [end] must have the same source URL and [start] must come
-  /// before [end]. [text] must have a number of characters equal to the
-  /// distance between [start] and [end].
-  factory SourceSpan(SourceLocation start, SourceLocation end, String text) =>
-      new SourceSpanBase(start, end, text);
-
-  /// Creates a new span that's the union of [this] and [other].
-  ///
-  /// The two spans must have the same source URL and may not be disjoint.
-  /// [text] is computed by combining [this.text] and [other.text].
-  SourceSpan union(SourceSpan other);
-
-  /// Compares two spans.
-  ///
-  /// [other] must have the same source URL as [this]. This orders spans by
-  /// [start] then [length].
-  int compareTo(SourceSpan other);
-
-  /// Formats [message] in a human-friendly way associated with this span.
-  ///
-  /// [color] may either be a [String], a [bool], or `null`. If it's a string,
-  /// it indicates an ANSII terminal color escape that should be used to
-  /// highlight the span's text. If it's `true`, it indicates that the text
-  /// should be highlighted using the default color. If it's `false` or `null`,
-  /// it indicates that the text shouldn't be highlighted.
-  String message(String message, {color});
-}
-
-/// A base class for source spans with [start], [end], and [text] known at
-/// construction time.
-class SourceSpanBase extends SourceSpanMixin {
-  final SourceLocation start;
-  final SourceLocation end;
-  final String text;
-
-  SourceSpanBase(this.start, this.end, this.text) {
-    if (end.sourceUrl != start.sourceUrl) {
-      throw new ArgumentError("Source URLs \"${start.sourceUrl}\" and "
-          " \"${end.sourceUrl}\" don't match.");
-    } else if (end.offset < start.offset) {
-      throw new ArgumentError('End $end must come after start $start.');
-    } else if (text.length != start.distance(end)) {
-      throw new ArgumentError('Text "$text" must be ${start.distance(end)} '
-          'characters long.');
-    }
-  }
-}