Add IfConstantConditionRule test for phpstan/phpstan#8270

The original bug report was about a false positive "If condition is always true."
error, so this adds a non-regression test in IfConstantConditionRuleTest.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Rules/Comparison/IfConstantConditionRuleTest.php

@@ -213,4 +213,10 @@ public function testBug4284(): void
 		]);
 	}
 
+	public function testBug8270(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-8270.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-8270.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug8270Rule;
+
+function () {
+	$list = [];
+
+	for ($i = 0; $i < 10; $i++) {
+		$list[] = [
+			'test' => false,
+			'value' => rand(),
+		];
+	}
+
+	if ($list === []) {
+		return;
+	}
+
+	$k = array_key_first($list);
+	$list[$k]['test'] = true;
+
+	foreach ($list as $item) {
+		if ($item['test']) {
+			echo $item['value'];
+		}
+	}
+};