From b92e25cf3edebebcf96c78f38601beea28e94834 Mon Sep 17 00:00:00 2001
From: ondrejmirtes <104888+ondrejmirtes@users.noreply.github.com>
Date: Fri, 27 Feb 2026 08:44:20 +0000
Subject: [PATCH] Preserve vacuously true conditional expressions during scope
 merging

Fixes https://github.com/phpstan/phpstan/issues/4173
---
 src/Analyser/MutatingScope.php                | 47 +++++++++++++++++++
 src/Analyser/NodeScopeResolver.php            |  2 +-
 .../InitializerExprTypeResolver.php           |  5 +-
 .../Variables/DefinedVariableRuleTest.php     | 27 ++---------
 4 files changed, 54 insertions(+), 27 deletions(-)

diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 4036f5ca72..1d5e4f2c9b 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -3956,6 +3956,16 @@ public function mergeWith(?self $otherScope): self
 
 		$mergedExpressionTypes = $this->mergeVariableHolders($ourExpressionTypes, $theirExpressionTypes);
 		$conditionalExpressions = $this->intersectConditionalExpressions($otherScope->conditionalExpressions);
+		$conditionalExpressions = $this->preserveVacuousConditionalExpressions(
+			$conditionalExpressions,
+			$this->conditionalExpressions,
+			$theirExpressionTypes,
+		);
+		$conditionalExpressions = $this->preserveVacuousConditionalExpressions(
+			$conditionalExpressions,
+			$otherScope->conditionalExpressions,
+			$ourExpressionTypes,
+		);
 		$conditionalExpressions = $this->createConditionalExpressions(
 			$conditionalExpressions,
 			$ourExpressionTypes,
@@ -4055,6 +4065,43 @@ private function intersectConditionalExpressions(array $otherConditionalExpressi
 		return $newConditionalExpressions;
 	}
 
+	/**
+	 * @param array<string, ConditionalExpressionHolder[]> $currentConditionalExpressions
+	 * @param array<string, ConditionalExpressionHolder[]> $sourceConditionalExpressions
+	 * @param array<string, ExpressionTypeHolder> $otherExpressionTypes
+	 * @return array<string, ConditionalExpressionHolder[]>
+	 */
+	private function preserveVacuousConditionalExpressions(
+		array $currentConditionalExpressions,
+		array $sourceConditionalExpressions,
+		array $otherExpressionTypes,
+	): array
+	{
+		foreach ($sourceConditionalExpressions as $exprString => $holders) {
+			foreach ($holders as $key => $holder) {
+				if (isset($currentConditionalExpressions[$exprString][$key])) {
+					continue;
+				}
+
+				foreach ($holder->getConditionExpressionTypeHolders() as $guardExprString => $guardTypeHolder) {
+					if (!array_key_exists($guardExprString, $otherExpressionTypes)) {
+						continue;
+					}
+
+					$otherType = $otherExpressionTypes[$guardExprString]->getType();
+					$guardType = $guardTypeHolder->getType();
+
+					if ($otherType->isSuperTypeOf($guardType)->no()) {
+						$currentConditionalExpressions[$exprString][$key] = $holder;
+						break;
+					}
+				}
+			}
+		}
+
+		return $currentConditionalExpressions;
+	}
+
 	/**
 	 * @param array<string, ConditionalExpressionHolder[]> $newConditionalExpressions
 	 * @param array<string, ConditionalExpressionHolder[]> $existingConditionalExpressions
diff --git a/src/Analyser/NodeScopeResolver.php b/src/Analyser/NodeScopeResolver.php
index 86f616953b..639e131448 100644
--- a/src/Analyser/NodeScopeResolver.php
+++ b/src/Analyser/NodeScopeResolver.php
@@ -3217,7 +3217,7 @@ function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $context, $sto
 					$this->callNodeCallback($nodeCallback, new InvalidateExprNode($normalizedExpr->var), $scope, $storage);
 					$scope = $scope->invalidateExpression($normalizedExpr->var, true, $methodReflection->getDeclaringClass());
 				}
-				if ($parametersAcceptor !== null && !$methodReflection->isStatic()) {
+				if (!$methodReflection->isStatic()) {
 					$selfOutType = $methodReflection->getSelfOutType();
 					if ($selfOutType !== null) {
 						$scope = $scope->assignExpression(
diff --git a/src/Reflection/InitializerExprTypeResolver.php b/src/Reflection/InitializerExprTypeResolver.php
index 2794147dcc..28add0f92d 100644
--- a/src/Reflection/InitializerExprTypeResolver.php
+++ b/src/Reflection/InitializerExprTypeResolver.php
@@ -2210,13 +2210,14 @@ private function integerRangeMath(Type $range, BinaryOp $node, Type $operand): T
 						$min = null;
 					}
 
-					if ($operand->getMax() === null) {
+					$operandMax = $operand->getMax();
+					if ($operandMax === null) {
 						$min = null;
 						$max = null;
 					} elseif ($rangeMax !== null) {
 						if ($rangeMin !== null && $operand->getMin() === null) {
 							/** @var int|float $min */
-							$min = $rangeMin - $operand->getMax();
+							$min = $rangeMin - $operandMax;
 							$max = null;
 						} elseif ($operand->getMin() !== null) {
 							/** @var int|float $max */
diff --git a/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php b/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
index 112a57d4cc..ffdbdffffb 100644
--- a/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
+++ b/tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php
@@ -911,12 +911,7 @@ public function testBug4173(): void
 		$this->polluteScopeWithLoopInitialAssignments = false;
 		$this->checkMaybeUndefinedVariables = true;
 		$this->polluteScopeWithAlwaysIterableForeach = true;
-		$this->analyse([__DIR__ . '/data/bug-4173.php'], [
-			[
-				'Variable $value might not be defined.', // could be fixed
-				30,
-			],
-		]);
+		$this->analyse([__DIR__ . '/data/bug-4173.php'], []);
 	}
 
 	public function testBug5805(): void
@@ -1119,29 +1114,13 @@ public function testDynamicAccess(): void
 				18,
 			],
 			[
-				'Variable $foo might not be defined.',
-				36,
-			],
-			[
-				'Variable $foo might not be defined.',
-				37,
-			],
-			[
-				'Variable $bar might not be defined.',
+				'Undefined variable: $bar',
 				38,
 			],
 			[
-				'Variable $bar might not be defined.',
-				40,
-			],
-			[
-				'Variable $foo might not be defined.',
+				'Undefined variable: $foo',
 				41,
 			],
-			[
-				'Variable $bar might not be defined.',
-				42,
-			],
 			[
 				'Undefined variable: $buz',
 				44,