Separately format lines when a multisplit is split.

lib/src/chunk.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 dart_style.src.chunk;
 
 import 'debug.dart';
 
 /// Tracks where a selection start or end point may appear in some piece of
 /// text.
@@ skipping 265 matching lines @@
   bool operator ==(other) => identical(this, other);
 }
 
 /// Delimits a range of chunks that must end up on the same line to avoid an
 /// additional cost.
 ///
 /// These are used to encourage the line splitter to try to keep things
 /// together, like parameter lists and binary operator expressions.
 class Span {
   /// Index of the first chunk contained in this span.
-  final int start;
+  int get start => _start;
+  int _start;
 
   /// Index of the last chunk contained in this span.
   int get end => _end;
   int _end;
 
   /// The cost applied when the span is split across multiple lines or `null`
   /// if the span is for a multisplit.
   final int cost;
 
-  Span(this.start, this.cost);
+  Span(this._start, this.cost);
 
   /// Marks this span as ending at [end].
   void close(int end) {
     assert(_end == null);
     _end = end;
   }
 
   String toString() {
     var result = "Span($start";
 
     if (end != null) {
       result += " - $end";
     } else {
       result += "...";
     }
 
     if (cost != null) result += " \$$cost";
 
     return result + ")";
   }
+
+  /// Shifts the indexes of the chunk down by [offset].
+  ///
+  /// This is used when a prefix of the chunk list gets pulled off by the
+  /// [LineWriter] after it gets formatted as a line. The remaining spans need
+  /// to have their indices shifted to account for the removed chunks.
+  ///
+  /// Returns `true` if the span has shifted all the way off the front and
+  /// should just be discarded.
+  bool shift(int offset) {
+    if (end != null && end < offset) return true;
+
+    _start -= offset;
+    if (_end != null) _end -= offset;
+
+    return false;
+  }
 }
 
 /// A comment in the source, with a bit of information about the surrounding
 /// whitespace.
 class SourceComment extends Selection {
   /// The text of the comment, including `//`, `/*`, and `*/`.
   final String text;
 
   /// The number of newlines between the comment or token preceding this comment
   /// and the beginning of this one.
   ///
   /// Will be zero if the comment is a trailing one.
   final int linesBefore;
 
   /// Whether this comment is a line comment.
   final bool isLineComment;
 
   /// Whether this comment starts at column one in the source.
   ///
   /// Comments that start at the start of the line will not be indented in the
   /// output. This way, commented out chunks of code do not get erroneously
   /// re-indented.
   final bool isStartOfLine;
 
   SourceComment(this.text, this.linesBefore,
       {this.isLineComment, this.isStartOfLine});
 }