Change Collection::slice() method to return an instance of Collection

instead of an array.

Author: jwage

UPGRADING-2.0.md

@@ -56,3 +56,7 @@ You can find a list of major changes to public API below.
 |             before           |                   after                  |
 |-----------------------------:|:-----------------------------------------|
 | matching(Criteria $criteria) | matching(Criteria $criteria): Collection |
+
+#### Doctrine\Common\Collections\Collection::slice()
+
+The `Collection::slice()` method returns a new `Collection` instance now instead of an array.

lib/Doctrine/Common/Collections/AbstractLazyCollection.php

@@ -268,7 +268,7 @@ public function indexOf($element)
     /**
      * {@inheritDoc}
      */
-    public function slice(int $offset, ?int $length = null) : array
+    public function slice(int $offset, ?int $length = null) : Collection
     {
         $this->initialize();
 

lib/Doctrine/Common/Collections/ArrayCollection.php

@@ -392,9 +392,9 @@ public function clear() : void
     /**
      * {@inheritDoc}
      */
-    public function slice(int $offset, ?int $length = null) : array
+    public function slice(int $offset, ?int $length = null) : Collection
     {
-        return array_slice($this->elements, $offset, $length, true);
+        return $this->createFrom(array_slice($this->elements, $offset, $length, true));
     }
 
     /**

lib/Doctrine/Common/Collections/Collection.php

@@ -286,9 +286,9 @@ public function indexOf($element);
      * @param int      $offset The offset to start from.
      * @param int|null $length The maximum number of elements to return, or null for no limit.
      *
-     * @return array
+     * @return Collection
      *
-     * @psalm-return array<TKey,T>
+     * @psalm-return Collection<TKey, T>
      */
-    public function slice(int $offset, ?int $length = null) : array;
+    public function slice(int $offset, ?int $length = null) : self;
 }

tests/Doctrine/Tests/Common/Collections/BaseCollectionTest.php

@@ -204,14 +204,14 @@ public function testSlice() : void
         $this->collection[] = 'two';
         $this->collection[] = 'three';
 
-        $slice = $this->collection->slice(0, 1);
+        $slice = $this->collection->slice(0, 1)->toArray();
         self::assertInternalType('array', $slice);
         self::assertEquals(['one'], $slice);
 
-        $slice = $this->collection->slice(1);
+        $slice = $this->collection->slice(1)->toArray();
         self::assertEquals([1 => 'two', 2 => 'three'], $slice);
 
-        $slice = $this->collection->slice(1, 1);
+        $slice = $this->collection->slice(1, 1)->toArray();
         self::assertEquals([1 => 'two'], $slice);
     }