Replace a use of putIfAbsent with ??= (dart-lang/collection#125)

Because it avoids using a closure, it seems that ??= [] can be used with better performance than putIfAbsent in groupBy.
dart-lang · Mar 18, 2020 · 5826da6 · 5826da6
1 parent 80e5149
commit 5826da6
Showing 1 changed file with 1 addition and 2 deletions.
diff --git a/pkgs/collection/lib/src/functions.dart b/pkgs/collection/lib/src/functions.dart
@@ -49,8 +49,7 @@ Map<K, V> mergeMaps<K, V>(Map<K, V> map1, Map<K, V> map2,
 Map<T, List<S>> groupBy<S, T>(Iterable<S> values, T Function(S) key) {
   var map = <T, List<S>>{};
   for (var element in values) {
-    var list = map.putIfAbsent(key(element), () => []);
-    list.add(element);
+    (map[key(element)] ??= []).add(element);
   }
   return map;
 }