Use self instead of Collection as a return type for Collection::copy()

Author: simPod

src/Collection.php

@@ -25,9 +25,9 @@ function count(): int;
     /**
      * Returns a shallow copy of the collection.
      *
-     * @return Collection a copy of the collection.
+     * @return static a copy of the collection.
      */
-    function copy(): Collection;
+    function copy();
 
     /**
      * Returns whether the collection is empty.

src/Pair.php

@@ -52,10 +52,8 @@ public function __unset($name)
 
     /**
      * Returns a copy of the Pair
-     *
-     * @return Pair
      */
-    public function copy(): Pair
+    public function copy(): self
     {
         return new self($this->key, $this->value);
     }

src/PriorityQueue.php

@@ -50,7 +50,7 @@ public function clear()
     /**
      * @inheritDoc
      */
-    public function copy(): \Ds\Collection
+    public function copy(): self
     {
         $copy = new PriorityQueue();
 

src/Queue.php

@@ -63,7 +63,7 @@ public function clear()
     /**
      * @inheritDoc
      */
-    public function copy(): \Ds\Collection
+    public function copy(): self
     {
         return new self($this->deque);
     }

src/Set.php

@@ -101,7 +101,7 @@ public function contains(...$values): bool
     /**
      * @inheritDoc
      */
-    public function copy(): \Ds\Collection
+    public function copy(): self
     {
         return new self($this);
     }

src/Stack.php

@@ -40,7 +40,7 @@ public function clear()
     /**
      * @inheritdoc
      */
-    public function copy(): Collection
+    public function copy(): self
     {
         return new self($this->vector);
     }

src/Traits/GenericCollection.php

@@ -39,7 +39,7 @@ public function jsonSerialize()
      */
     public function copy(): self
     {
-        return new self($this);
+        return new static($this);
     }
 
     /**