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]) {}',
+ ];
  }
 }