Fix assignment in key of array destructuring being ignored

- Propagate scope from key expression processing in list/array destructuring
- Previously the scope result from processing key expressions was discarded,
  so assignments like `[($a = 'foo') => $b] = [...]` left `$a` undefined
- New regression test in tests/PHPStan/Analyser/nsrt/bug-14019.php

Closes phpstan/phpstan#14019

Author: ondrejmirtes

src/Analyser/ExprHandler/AssignHandler.php

@@ -688,7 +688,7 @@ public function processAssignVar(
 					$throwPoints = array_merge($throwPoints, $keyResult->getThrowPoints());
 					$impurePoints = array_merge($impurePoints, $keyResult->getImpurePoints());
 					$isAlwaysTerminating = $isAlwaysTerminating || $keyResult->isAlwaysTerminating();
-					// no need for $keyResult->getScope()
+					$scope = $keyResult->getScope();
 				}
 
 				if ($arrayItem->key === null) {

tests/PHPStan/Analyser/nsrt/bug-14019.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14019;
+
+use function PHPStan\Testing\assertType;
+
+[($a = 'foo') => $b] = ['foo' => 1];
+
+assertType("'foo'", $a);
+assertType('1', $b);