Various improvements

src/Relations/BelongsToThrough.php

@@ -7,7 +7,6 @@
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Database\Eloquent\SoftDeletes;
-use Illuminate\Database\Query\Expression;
 use Illuminate\Support\Str;
 
 class BelongsToThrough extends Relation
@@ -128,7 +127,7 @@ protected function getForeignKeyName(Model $model)
      */
     public function hasSoftDeletes(Model $model)
     {
-        return in_array(SoftDeletes::class, class_uses_recursive(get_class($model)));
+        return in_array(SoftDeletes::class, class_uses_recursive($model));
     }
 
     /**
@@ -262,9 +261,7 @@ public function getRelationExistenceQuery(Builder $query, Builder $parent, $colu
 
         $foreignKey = $parent->getQuery()->from.'.'.$this->getFirstForeignKeyName();
 
-        $foreignKey = new Expression($query->getQuery()->getGrammar()->wrap($foreignKey));
-
-        return $query->select($columns)->where(
+        return $query->select($columns)->whereColumn(
             $this->getQualifiedFirstLocalKeyName(),
             '=',
             $foreignKey
@@ -316,4 +313,15 @@ public function getQualifiedFirstLocalKeyName()
     {
         return end($this->throughParents)->getQualifiedKeyName();
     }
+
+    /**
+     * Make a new related instance for the given model.
+     *
+     * @param \Illuminate\Database\Eloquent\Model $parent
+     * @return \Illuminate\Database\Eloquent\Model
+     */
+    protected function newRelatedInstanceFor(Model $parent)
+    {
+        return $this->related->newInstance();
+    }
 }

src/Traits/BelongsToThrough.php

@@ -20,8 +20,7 @@ trait BelongsToThrough
      */
     public function belongsToThrough($related, $through, $localKey = null, $prefix = '', $foreignKeyLookup = [])
     {
-        /** @var \Illuminate\Database\Eloquent\Model $relatedInstance */
-        $relatedInstance = new $related;
+        $relatedInstance = $this->newRelatedInstance($related);
         $throughParents = [];
         $foreignKeys = [];