From 84c45e22f0e7ef011561d6098d491c94bb4a5dc8 Mon Sep 17 00:00:00 2001
From: ondrejmirtes <104888+ondrejmirtes@users.noreply.github.com>
Date: Sun, 22 Feb 2026 18:00:15 +0000
Subject: [PATCH] Fix conditional expression holder chain resolution regression

- Iterating conditional expression holders in filterBySpecifiedTypes
  now loops until convergence, making it order-independent
- The previous commit (3daa3128a, Fix #13303) changed
  mergeConditionalExpressions to put existing holders before new ones,
  breaking chains where a new holder must fire before an existing one
- Updated dependent-variable-certainty and dependent-expression-certainty
  tests to reflect improved certainty resolution (Maybe -> Yes)
- New regression test in tests/PHPStan/Analyser/nsrt/bug-14178.php

Fixes phpstan/phpstan#14178
---
 src/Analyser/MutatingScope.php                | 23 ++++++----
 tests/PHPStan/Analyser/nsrt/bug-14178.php     | 43 +++++++++++++++++++
 .../nsrt/dependent-expression-certainty.php   |  2 +-
 .../nsrt/dependent-variable-certainty.php     |  2 +-
 4 files changed, 60 insertions(+), 10 deletions(-)
 create mode 100644 tests/PHPStan/Analyser/nsrt/bug-14178.php

diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 0e3004bddaf..78292314484 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -3805,16 +3805,23 @@ public function filterBySpecifiedTypes(SpecifiedTypes $specifiedTypes): self
 		}
 
 		$conditions = [];
-		foreach ($scope->conditionalExpressions as $conditionalExprString => $conditionalExpressions) {
-			foreach ($conditionalExpressions as $conditionalExpression) {
-				foreach ($conditionalExpression->getConditionExpressionTypeHolders() as $holderExprString => $conditionalTypeHolder) {
-					if (!array_key_exists($holderExprString, $specifiedExpressions) || !$specifiedExpressions[$holderExprString]->equals($conditionalTypeHolder)) {
-						continue 2;
-					}
+		$prevSpecifiedCount = -1;
+		while (count($specifiedExpressions) !== $prevSpecifiedCount) {
+			$prevSpecifiedCount = count($specifiedExpressions);
+			foreach ($scope->conditionalExpressions as $conditionalExprString => $conditionalExpressions) {
+				if (array_key_exists($conditionalExprString, $conditions)) {
+					continue;
 				}
+				foreach ($conditionalExpressions as $conditionalExpression) {
+					foreach ($conditionalExpression->getConditionExpressionTypeHolders() as $holderExprString => $conditionalTypeHolder) {
+						if (!array_key_exists($holderExprString, $specifiedExpressions) || !$specifiedExpressions[$holderExprString]->equals($conditionalTypeHolder)) {
+							continue 2;
+						}
+					}
 
-				$conditions[$conditionalExprString][] = $conditionalExpression;
-				$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
+					$conditions[$conditionalExprString][] = $conditionalExpression;
+					$specifiedExpressions[$conditionalExprString] = $conditionalExpression->getTypeHolder();
+				}
 			}
 		}
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14178.php b/tests/PHPStan/Analyser/nsrt/bug-14178.php
new file mode 100644
index 00000000000..c3c0035f126
--- /dev/null
+++ b/tests/PHPStan/Analyser/nsrt/bug-14178.php
@@ -0,0 +1,43 @@
+<?php declare(strict_types = 1);
+
+namespace Bug14178;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld {
+	/**
+	 * @return list<string>
+	 */
+	public static function diff(
+		?self $previousVersion,
+		?self $newVersion,
+	): array {
+		$previousVersionExists = $previousVersion !== null;
+		$newVersionExists = $newVersion !== null;
+
+		if (!$previousVersionExists && !$newVersionExists) {
+			return [];
+		}
+
+		if ($previousVersionExists && !$newVersionExists) {
+			return ['bar'];
+		}
+
+		if (!$previousVersionExists) {
+			assertType('true', $newVersionExists);
+			assertType('Bug14178\\HelloWorld', $newVersion);
+			$result = [];
+			$result[] = 'foo';
+			$categoryString = implode(', ', $newVersion->getSomething());
+		}
+
+		return [];
+	}
+
+	/**
+	 * @return array<string>
+	 */
+	private function getSomething(): array {
+		return ['foo'];
+	}
+}
diff --git a/tests/PHPStan/Analyser/nsrt/dependent-expression-certainty.php b/tests/PHPStan/Analyser/nsrt/dependent-expression-certainty.php
index 302d82b609d..d8596c0a21c 100644
--- a/tests/PHPStan/Analyser/nsrt/dependent-expression-certainty.php
+++ b/tests/PHPStan/Analyser/nsrt/dependent-expression-certainty.php
@@ -153,7 +153,7 @@ function (bool $a, bool $b) {
 
 	assertVariableCertainty(TrinaryLogic::createMaybe(), $foo);
 	if (returnsBool($b)) {
-		assertVariableCertainty(TrinaryLogic::createMaybe(), $foo); // could be Yes
+		assertVariableCertainty(TrinaryLogic::createYes(), $foo);
 	}
 
 	if (returnsBool($a)) {
diff --git a/tests/PHPStan/Analyser/nsrt/dependent-variable-certainty.php b/tests/PHPStan/Analyser/nsrt/dependent-variable-certainty.php
index f84857da660..8e34c91b91e 100644
--- a/tests/PHPStan/Analyser/nsrt/dependent-variable-certainty.php
+++ b/tests/PHPStan/Analyser/nsrt/dependent-variable-certainty.php
@@ -149,7 +149,7 @@ function (bool $a, bool $b) {
 
 	assertVariableCertainty(TrinaryLogic::createMaybe(), $foo);
 	if ($b) {
-		assertVariableCertainty(TrinaryLogic::createMaybe(), $foo); // could be Yes
+		assertVariableCertainty(TrinaryLogic::createYes(), $foo);
 	}
 
 	if ($a) {