use short closures where possible (#46102)

short closures are a little more succinct for readability, and this gives is more consistency throughout the `Collection` class, as we had a mix of short vs long closures.

Author: browner12

src/Illuminate/Collections/Collection.php

@@ -84,11 +84,8 @@ public function avg($callback = null)
     {
         $callback = $this->valueRetriever($callback);
 
-        $items = $this->map(function ($value) use ($callback) {
-            return $callback($value);
-        })->filter(function ($value) {
-            return ! is_null($value);
-        });
+        $items = $this->map(fn ($value) => $callback($value))
+                      ->filter(fn ($value) => ! is_null($value));
 
         if ($count = $items->count()) {
             return $items->sum() / $count;
@@ -349,14 +346,10 @@ public function duplicatesStrict($callback = null)
     protected function duplicateComparator($strict)
     {
         if ($strict) {
-            return function ($a, $b) {
-                return $a === $b;
-            };
+            return fn ($a, $b) => $a === $b;
         }
 
-        return function ($a, $b) {
-            return $a == $b;
-        };
+        return fn ($a, $b) => $a == $b;
     }
 
     /**
@@ -1151,9 +1144,7 @@ public function sliding($size = 2, $step = 1)
     {
         $chunks = floor(($this->count() - $size) / $step) + 1;
 
-        return static::times($chunks, function ($number) use ($size, $step) {
-            return $this->slice(($number - 1) * $step, $size);
-        });
+        return static::times($chunks, fn ($number) => $this->slice(($number - 1) * $step, $size));
     }
 
     /**
@@ -1634,13 +1625,9 @@ public function values()
      */
     public function zip($items)
     {
-        $arrayableItems = array_map(function ($items) {
-            return $this->getArrayableItems($items);
-        }, func_get_args());
+        $arrayableItems = array_map(fn ($items) => $this->getArrayableItems($items), func_get_args());
 
-        $params = array_merge([function () {
-            return new static(func_get_args());
-        }, $this->items], $arrayableItems);
+        $params = array_merge([fn () => new static(func_get_args()), $this->items], $arrayableItems);
 
         return new static(array_map(...$params));
     }