Add tests for FilterVarThrowTypeExtension and FilterVarRule on PHP < 8.5

- Add nsrt test verifying filter_var with FILTER_THROW_ON_FAILURE still
  returns false on PHP < 8.5 (throw type extension correctly inactive)
- Add FilterVarRule test verifying no error for FILTER_NULL_ON_FAILURE +
  FILTER_THROW_ON_FAILURE combination on PHP < 8.5

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

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-14397-pre-php85.php

@@ -0,0 +1,16 @@
+<?php // lint < 8.5
+
+declare(strict_types = 1);
+
+namespace Bug14397PrePhp85;
+
+use function filter_var;
+use function PHPStan\Testing\assertType;
+
+function test(mixed $mixed): void
+{
+	// On PHP < 8.5, FILTER_THROW_ON_FAILURE doesn't truly exist
+	// so it shouldn't remove false from the return type
+	assertType('int|false', filter_var($mixed, FILTER_VALIDATE_INT, FILTER_THROW_ON_FAILURE));
+	assertType('int|false', filter_var($mixed, FILTER_VALIDATE_INT, ['flags' => FILTER_THROW_ON_FAILURE]));
+}

tests/PHPStan/Rules/Functions/FilterVarRuleTest.php

@@ -31,4 +31,10 @@ public function testRule(): void
 		]);
 	}
 
+	#[RequiresPhp('< 8.5')]
+	public function testRuleBeforePhp85(): void
+	{
+		$this->analyse([__DIR__ . '/data/filter_var_null_and_throw_pre_php85.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Functions/data/filter_var_null_and_throw_pre_php85.php

@@ -0,0 +1,16 @@
+<?php // lint < 8.5
+
+namespace FilterVarNullAndThrowPrePhp85;
+
+// On PHP < 8.5, FILTER_THROW_ON_FAILURE doesn't truly exist
+// so combining it with FILTER_NULL_ON_FAILURE should not be an error
+filter_var('foo@bar.test', FILTER_VALIDATE_EMAIL, FILTER_THROW_ON_FAILURE|FILTER_NULL_ON_FAILURE);
+
+$flag = FILTER_NULL_ON_FAILURE|FILTER_THROW_ON_FAILURE;
+filter_var(100, FILTER_VALIDATE_INT, $flag);
+
+filter_var(
+	'johndoe',
+	FILTER_VALIDATE_REGEXP,
+	['options' => ['regexp' => '/^[a-z]+$/'], 'flags' => FILTER_THROW_ON_FAILURE|FILTER_NULL_ON_FAILURE]
+);