Traditionally, to iterate over the keys and values of a Map you can write this:

  map.forEach((key, value) {

  });

But with the introduction of patterns in Dart 3.0 you could actually write it as

  for (var MapEntry(:key, :value) in map.entries) {

  }

In fact, such a construction is given as example at the patterns documentation in the For and for-in loops section.

I suppose whether it’s a better code style is subjective, but is one way better than the other in terms of performance/memory?