Make traits more generic

Type hinting User should take place in the callbacks. Theoretically
these traits could be used for another project now, where something
else has permissions (like a Sheep class, or a number)

src/Core/Support/Locked.php

@@ -1,8 +1,6 @@
 <?php namespace Flarum\Core\Support;
 
 use Flarum\Core\Exceptions\PermissionDeniedException;
-use Flarum\Core\Models\User;
-use Closure;
 
 trait Locked
 {
@@ -16,7 +14,7 @@ trait Locked
         return array_merge($conditions, $all);
     }
 
-    public static function allow($action, Closure $condition)
+    public static function allow($action, callable $condition)
     {
         foreach ((array) $action as $action) {
             if (! isset(static::$conditions[$action])) {
@@ -27,7 +25,7 @@ trait Locked
         }
     }
 
-    public function can(User $user, $action)
+    public function can($user, $action)
     {
         foreach ($this->getConditions($action) as $condition) {
             $can = $condition($this, $user, $action);
@@ -48,7 +46,7 @@ trait Locked
      *
      * @throws \Flarum\Core\Exceptions\PermissionDeniedException
      */
-    public function assertCan(User $user, $action)
+    public function assertCan($user, $action)
     {
         if (! $this->can($user, $action)) {
             throw new PermissionDeniedException;

src/Core/Support/VisibleScope.php

@@ -1,17 +1,15 @@
 <?php namespace Flarum\Core\Support;
 
-use Flarum\Core\Models\User;
-
 trait VisibleScope
 {
     protected static $visibleScopes = [];
 
-    public static function scopeVisible($scope)
+    public static function addVisibleScope(callable $scope)
     {
         static::$visibleScopes[] = $scope;
     }
 
-    public function scopeWhereVisibleTo($query, User $user)
+    public function scopeWhereVisibleTo($query, $user)
     {
         foreach (static::$visibleScopes as $scope) {
             $scope($query, $user);

src/Extend/Model.php

@@ -82,7 +82,7 @@ class Model implements ExtenderInterface
         }
 
         foreach ($this->scopeVisible as $callback) {
-            $model::scopeVisible($callback);
+            $model::addVisiblePostsScope($callback);
         }
 
         foreach ($this->allow as $info) {