Merge occurrences.

pkg/analysis_server/lib/src/domains/analysis/occurrences.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 domains.analysis.occurrences;
 
 import 'package:analysis_server/analysis/occurrences_core.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analyzer/src/generated/engine.dart'
@@ skipping 18 matching lines @@
           new CaughtException(exception, stackTrace));
     }
   }
   return collector;
 }
 
 /**
  * A concrete implementation of [OccurrencesCollector].
  */
 class OccurrencesCollectorImpl implements OccurrencesCollector {
-  final List<protocol.Occurrences> allOccurrences = <protocol.Occurrences>[];
+  Map<protocol.Element, protocol.Occurrences> elementOccurrences =
+      <protocol.Element, protocol.Occurrences>{};
+
+  List<protocol.Occurrences> get allOccurrences {
+    return elementOccurrences.values.toList();
+  }
 
   @override
-  void addOccurrences(protocol.Occurrences occurrences) {
-    allOccurrences.add(occurrences);
+  void addOccurrences(protocol.Occurrences current) {
+    protocol.Element element = current.element;
+    protocol.Occurrences existing = elementOccurrences[element];
+    if (existing != null) {
+      List<int> offsets = _merge(existing.offsets, current.offsets);
+      current = new protocol.Occurrences(element, offsets, existing.length);
+    }
+    elementOccurrences[element] = current;
+  }
+
+  static List<int> _merge(List<int> a, List<int> b) {
+    return <int>[]..addAll(a)..addAll(b);
   }
 }