Change return types of through (pagination) and transform (collection) (#56105)

Author: glamorous

src/Illuminate/Collections/Collection.php

@@ -1729,8 +1729,10 @@ public function takeWhile($value)
  /**
  * Transform each item in the collection using a callback.
  *
- * @param callable(TValue, TKey): TValue $callback
- * @return $this
+ * @template TMapValue
+ *
+ * @param callable(TValue, TKey): TMapValue $callback
+ * @return $this<TKey, TMapValue>
  */
  public function transform(callable $callback)
  {

src/Illuminate/Pagination/AbstractPaginator.php

@@ -353,8 +353,10 @@ public function lastItem()
  /**
  * Transform each item in the slice of items using a callback.
  *
- * @param callable $callback
- * @return $this
+ * @template TMapValue
+ *
+ * @param callable(TValue, TKey): TMapValue $callback
+ * @return $this<TKey, TMapValue>
  */
  public function through(callable $callback)
  {

types/Support/Collection.php

@@ -1049,13 +1049,20 @@ function ($collection, $count) {
 assertType('Illuminate\Support\Collection<int, User>', $collection->splice(1));
 assertType('Illuminate\Support\Collection<int, User>', $collection->splice(1, 1, [new User]));
 
-assertType('Illuminate\Support\Collection<int, User>', $collection->transform(function ($user, $int) {
+assertType('mixed', $collection->transform(function ($user, $int) {
  assertType('User', $user);
  assertType('int', $int);
 
  return new User;
 }));
 
+assertType('mixed', $collection->transform(function ($user, $int): int {
+ assertType('User', $user);
+ assertType('int', $int);
+
+ return $int * 2;
+}));
+
 assertType('Illuminate\Support\Collection<int, User>', $collection->add(new User));
 
 /**