Rework recent changes to LineInfo to be backward compatible.

pkg/analyzer/lib/src/generated/source.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 analyzer.src.generated.source;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 179 matching lines @@
   /**
    * The zero-based [_lineStarts] index resulting from the last call to
    * [getLocation].
    */
   int _previousLine = 0;
 
   /**
    * Initialize a newly created set of line information to represent the data
    * encoded in the given list of [_lineStarts].
    */
-  LineInfo(this._lineStarts) {
+  factory LineInfo(List<int> _lineStarts) => new LineInfoWithCount(_lineStarts);
+
+  /**
+   * Initialize a newly created set of line information to represent the data
+   * encoded in the given list of [_lineStarts].
+   */
+  LineInfo._(this._lineStarts) {
     if (_lineStarts == null) {
       throw new IllegalArgumentException("lineStarts must be non-null");
     } else if (_lineStarts.length < 1) {
       throw new IllegalArgumentException("lineStarts must be non-empty");
     }
   }
 
   /**
-   * Return the number of lines in the file.
-   */
-  int get lineCount => _lineStarts.length;
-
-  /**
    * Return the location information for the character at the given [offset].
    */
   LineInfo_Location getLocation(int offset) {
     var min = 0;
     var max = _lineStarts.length - 1;
 
     // Subsequent calls to [getLocation] are often for offsets near each other.
     // To take advantage of that, we cache the index of the line start we found
     // when this was last called. If the current offset is on that line or
     // later, we'll skip those early indices completely when searching.
@@ skipping 57 matching lines @@
    * @param lineNumber the one-based index of the line containing the character
    * @param columnNumber the one-based index of the column containing the character
    */
   LineInfo_Location(this.lineNumber, this.columnNumber);
 
   @override
   String toString() => '$lineNumber:$columnNumber';
 }
 
 /**
+ * Information about line and column information within a source file,
+ * including a count of the total number of lines.
+ *
+ * TODO(paulberry): in the next major version roll of analyzer, merge this
+ * class into [LineInfo].
+ */
+class LineInfoWithCount extends LineInfo {
+  /**
+   * Initialize a newly created set of line information to represent the data
+   * encoded in the given list of [_lineStarts].
+   */
+  LineInfoWithCount(List<int> _lineStarts) : super._(_lineStarts);
+
+  /**
+   * Return the number of lines in the file.
+   */
+  int get lineCount => _lineStarts.length;
+}
+
+/**
  * Instances of interface `LocalSourcePredicate` are used to determine if the given
  * [Source] is "local" in some sense, so can be updated.
  */
 abstract class LocalSourcePredicate {
   /**
    * Instance of [LocalSourcePredicate] that always returns `false`.
    */
   static final LocalSourcePredicate FALSE = new LocalSourcePredicate_FALSE();
 
   /**
@@ skipping 795 matching lines @@
   Source resolveAbsolute(Uri uri, [Uri actualUri]);
 
   /**
    * Return an absolute URI that represents the given [source], or `null` if a
    * valid URI cannot be computed.
    *
    * The computation should be based solely on [source.fullName].
    */
   Uri restoreAbsolute(Source source) => null;
 }