From b650945361334f3d42cb88ded847cd1e346bf127 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Sat, 28 Feb 2026 13:57:14 +0000
Subject: [PATCH] Fix array_filter with assert-if-true callable marking all
 keys optional

- When array_filter callback has @phpstan-assert-if-true, check the falsey branch
  to determine if the callback can actually return false for the given input type
- If filtering by falsey value makes the item/key type NeverType, the false branch
  is impossible, so the key should not be marked optional
- New regression test in tests/PHPStan/Analyser/nsrt/bug-11730.php

Closes https://github.com/phpstan/phpstan/issues/11730
---
 .../ArrayFilterFunctionReturnTypeHelper.php   | 18 ++++++++++----
 tests/PHPStan/Analyser/nsrt/bug-11730.php     | 24 +++++++++++++++++++
 2 files changed, 38 insertions(+), 4 deletions(-)
 create mode 100644 tests/PHPStan/Analyser/nsrt/bug-11730.php

diff --git a/src/Type/Php/ArrayFilterFunctionReturnTypeHelper.php b/src/Type/Php/ArrayFilterFunctionReturnTypeHelper.php
index 04ef90fef5..6c71da8a1c 100644
--- a/src/Type/Php/ArrayFilterFunctionReturnTypeHelper.php
+++ b/src/Type/Php/ArrayFilterFunctionReturnTypeHelper.php
@@ -260,12 +260,22 @@ private function processKeyAndItemType(MutatingScope $scope, Type $keyType, Type
 			return [new NeverType(), new NeverType(), false];
 		}
 
-		$scope = $scope->filterByTruthyValue($expr);
+		$truthyScope = $scope->filterByTruthyValue($expr);
+
+		$optional = !$booleanResult->isTrue()->yes();
+		if ($optional) {
+			$falseyScope = $scope->filterByFalseyValue($expr);
+			$falseyItemType = $itemVarName !== null ? $falseyScope->getVariableType($itemVarName) : $itemType;
+			$falseyKeyType = $keyVarName !== null ? $falseyScope->getVariableType($keyVarName) : $keyType;
+			if ($falseyItemType instanceof NeverType || $falseyKeyType instanceof NeverType) {
+				$optional = false;
+			}
+		}
 
 		return [
-			$keyVarName !== null ? $scope->getVariableType($keyVarName) : $keyType,
-			$itemVarName !== null ? $scope->getVariableType($itemVarName) : $itemType,
-			!$booleanResult->isTrue()->yes(),
+			$keyVarName !== null ? $truthyScope->getVariableType($keyVarName) : $keyType,
+			$itemVarName !== null ? $truthyScope->getVariableType($itemVarName) : $itemType,
+			$optional,
 		];
 	}
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-11730.php b/tests/PHPStan/Analyser/nsrt/bug-11730.php
new file mode 100644
index 0000000000..42299b511e
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-11730.php
@@ -0,0 +1,24 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace Bug11730;
+
+use function PHPStan\Testing\assertType;
+
+class Foo {}
+
+/** @return ($value is Foo ? true : false) */
+function isFoo(mixed $value): bool {
+	return $value instanceof Foo;
+}
+
+/** @phpstan-assert-if-true Foo $value */
+function checkFoo(mixed $value): bool {
+	return $value instanceof Foo;
+}
+
+$data = [new Foo, new Foo];
+
+assertType('array{Bug11730\Foo, Bug11730\Foo}', array_filter($data, isFoo(...)));
+assertType('array{Bug11730\Foo, Bug11730\Foo}', array_filter($data, checkFoo(...)));