Enhance precision of recorded instantiation info in ResolutionWorldBuilder

tests/compiler/dart2js/serialization/test_helper.dart

 // Copyright (c) 2016, 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 dart2js.serialization_test_helper;
 
 import 'dart:collection';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/constants/values.dart';
@@ skipping 190 matching lines @@
     Iterable set1, Iterable set2, List<List> common, List unfound,
     {bool sameElement(a, b): equality, void checkElements(a, b)}) {
   // TODO(johnniwinther): Avoid the quadratic cost here. Some ideas:
   // - convert each set to a list and sort it first, then compare by walking
   // both lists in parallel
   // - map each element to a canonical object, create a map containing those
   // mappings, use the mapped sets to compare (then operations like
   // set.difference would work)
   Set remaining = set2.toSet();
   for (var element1 in set1) {
+    bool found = false;
     var correspondingElement;
     for (var element2 in remaining) {
       if (sameElement(element1, element2)) {
         if (checkElements != null) {
           checkElements(element1, element2);
         }
+        found = true;
         correspondingElement = element2;
         remaining.remove(element2);
         break;
       }
     }
-    if (correspondingElement != null) {
+    if (found) {
       common.add([element1, correspondingElement]);
     } else {
       unfound.add(element1);
     }
   }
   return remaining;
 }
 
 /// Check equivalence of the two iterables, [set1] and [set1], as sets using
 /// [elementEquivalence] to compute the pair-wise equivalence.
@@ skipping 409 matching lines @@
   }
 
   if (index == 1 && skip != 0) {
     return ['${skip}', segmentNumber(index)];
   } else if (index == count) {
     return [segmentNumber(index - 1)];
   } else {
     return [segmentNumber(index - 1), segmentNumber(index)];
   }
 }