Optimize splitting lines with many rules.

lib/src/line_splitting/line_splitter.dart

 // Copyright (c) 2015, 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.line_splitting.line_splitter;
 
 import '../chunk.dart';
 import '../debug.dart' as debug;
 import '../line_writer.dart';
 import '../rule/rule.dart';
@@ skipping 127 matching lines @@
             .toList(growable: false),
         blockIndentation = blockIndentation,
         firstLineIndent = flushLeft ? 0 : firstLineIndent + blockIndentation {
     _queue.bindSplitter(this);
 
     // Store the rule's index in the rule so we can get from a chunk to a rule
     // index quickly.
     for (var i = 0; i < rules.length; i++) {
       rules[i].index = i;
     }
+
+    // Now that every used rule has an index, tell the rules to discard any
+    // constraints on unindexed rules.
+    for (var rule in rules) {
+      rule.forgetUnusedRules();
+    }
   }
 
   /// Determine the best way to split the chunks into lines that fit in the
   /// page, if possible.
   ///
   /// Returns a [SplitSet] that defines where each split occurs and the
   /// indentation of each line.
   ///
   /// [firstLineIndent] is the number of characters of whitespace to prefix the
   /// first line of output with.
@@ skipping 32 matching lines @@
       debug.log();
     }
 
     return _bestSolution.splits;
   }
 
   void enqueue(SolveState state) {
     _queue.add(state);
   }
 }