framework: [5.3.26] BelongsToMany withCount selects incorrect id.

• Laravel Version: 5.3.26
• PHP Version: 7.0.13
• Database Driver & Version: MariaDB-10.1.19

Description:

With a belongsToMany => belongsToMany, using the Builder::withCount() causes the incorrect id to be selected, it appears the id from the pivot table is being selected rather than the table itself.

Here are the models:

• User (users)

class User extends Model {
   ...
   public function roles() {
      return $this->belongsToMany(Role::class);
   }
   ...
}

users

id	name	email
9	Some Name	name@example.com

• Role (roles)(role_user)(permission_role)

class Role extends Model {
   ...
   public function permissions() {
      return $this->belongsToMany(Permission::class);
   }
   ...
}

roles

id	name	description
2	Administrator	Some description here

role_user

id	role_id	user_id
4	2	9

permission_role

id	permission_id	role_id
12	19	2
13	20	2
14	17	2
15	21	2

• Permission (permissions)

class Permission extends Model {
   ...
}

Steps To Reproduce:

1. Grab the roles for the user with the permission count.

$roles = $user->roles()->withCount('permissions')->get()

1. Check the first role id.

$role_id = $roles->first()->id;

1. The givenid is 4 (from the role_user table), when it should be 2 (from the roles table).

array(
   "id" => 4, // this should be 2.
   "name" => "Administrator",
   "description" => "Some description here",
   "role_id" => 2,
   "user_id" => 9,
   "permissions_count" => 4,
)

Additionally: the role_id and the user_id should be in a pivot key.