Add rule test for phpstan/phpstan#6822 to prove no false-positive rule error

The nsrt test only verified type inference. This adds an IfConstantConditionRule
test to prove that impure closures don't cause false "If condition is always true"
errors when used in nested conditions.

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 testBug6822(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-6822.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Comparison/data/bug-6822.php

@@ -0,0 +1,25 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6822Rule;
+
+/** @phpstan-impure */
+$closure = function (): bool {
+	return (bool) rand(0, 1);
+};
+
+if ($closure()) {
+	if ($closure()) { // should not be reported as "always true"
+		echo 'yes';
+	}
+}
+
+/** @phpstan-impure */
+$impureFn = function (): int {
+	return rand(0, 100);
+};
+
+if ($impureFn() > 50) {
+	if ($impureFn() > 50) { // should not be reported as "always true"
+		echo 'yes';
+	}
+}