Allow missing elements when destructuring arrays in foreach loops (#1880

)

* Allow missing elements when destructuring arrays in foreach loops

* Delete an unused import

* Move the check to `canMutate`

src/Mutator/Removal/ArrayItemRemoval.php

@@ -46,7 +46,6 @@
 use PhpParser\Node;
 use PhpParser\Node\Expr\ArrayItem;
 use function range;
-use Webmozart\Assert\Assert;
 
 /**
  * @internal
@@ -116,8 +115,6 @@ public static function getDefinition(): ?Definition
      */
     public function mutate(Node $node): iterable
     {
-        Assert::allNotNull($node->items);
-
         foreach ($this->getItemsIndexes($node->items) as $indexToRemove) {
             $newArrayNode = clone $node;
             unset($newArrayNode->items[$indexToRemove]);
@@ -147,13 +144,18 @@ public function canMutate(Node $node): bool
             return false;
         }
 
+        // Don't mutate destructured values in foreach loops
+        if ($parent instanceof Node\Stmt\Foreach_ && $parent->valueVar === $node) {
+            return false;
+        }
+
         return true;
     }
 
     /**
      * @psalm-mutation-free
      *
-     * @param ArrayItem[] $items
+     * @param array<array-key, ArrayItem|null> $items
      *
      * @return int[]
      */

tests/phpunit/Mutator/Removal/ArrayItemRemovalTest.php

@@ -122,5 +122,9 @@ public function mutationsProvider(): iterable
         yield 'It does not mutate arrays as an attribute argument' => [
             MutatorFixturesProvider::getFixtureFileContent($this, 'does-not-mutate-array-in-attribute.php'),
         ];
+
+        yield 'It does not mutate destructured array values in foreach loops' => [
+            '<?php foreach ($items as [, $value]) {}',
+        ];
     }
 }