• Larastan Version: v2.9.9
• Laravel Version: v11.23.5
• Phpstan Version: 1.12.6

Description

groupBy('status') returns int|string for TKey. I think that's acceptable, because Larastan doesn't know what status is. It probably could, but that's not the point. After that, I want to count how many records per group: ->map->count() so TValue should be int, and Larastan does that. But it also makes TKey int! Why would it go from int|string to int? The keys haven't changed from the higher-order-map.

Laravel code where the issue was found

$users = User::all();
\PHPStan\dumpType($users); // 🟩 App\Base\ModelCollection<int, App\Models\User>

$groups = $users->groupBy('status');
\PHPStan\dumpType($groups); // 🟩 App\Base\ModelCollection<(int|string), App\Base\ModelCollection<int, App\Models\User>>

$counts = $groups->map->count();
\PHPStan\dumpType($counts); // 🟥 Illuminate\Support\Collection<int, int>

The inner collection of $groups is int key 👍 because of the groupBy(). Maybe that's why the outer collection becomes int after map->count()? I'm just guessing.