[5.4] Make date/datetime cast difference more explicit by removing time part.

[jarnovanleeuwen]

Hi,

Currently, both date and datetime cast types are using the same casting method. However, this can lead to unexpected results when a UNIX timestamp or Carbon instance containing a time part is assigned to a date attribute. date attributes keep the time part when it is known, but after saving the model and refreshing it, the time part might be lost. Example:

use Carbon\Carbon;
use Illuminate\Database\Eloquent\Model;
class User extends Model
{
    protected $casts = [
        'date_of_birth' => 'date'
    ];
}

$dob = Carbon::now(); // 2016-12-14 15:18:34
$today = Carbon::today(); // 2016-12-14 00:00:00

$user = new User;
$user->date_of_birth = $dob;
$user->save();

if ($dob->eq($today)) {
    print "Born today";
} else {
    print "Not born today";
}

$user = $user->fresh();

if ($dob->eq($today)) {
    print "Born today";
} else {
    print "Not born today";
}

// Actual output:
// Not born today
// Born today

// Expected output:
// Born today
// Born today

As the cast types explicitly include both date and datetime, I think a more consistent approach would be to always remove the time part from date attributes.

Kind regards,
Jarno