Fix phpstan/phpstan#13981: Assignment inside match statement no longer recognized (#5120)

Co-authored-by: staabm <120441+staabm@users.noreply.github.com>
Co-authored-by: Vincent Langlet <vincentlanglet@hotmail.fr>

Author: 3 people

src/Analyser/NodeScopeResolver.php

@@ -4438,6 +4438,8 @@ function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $context, $sto
 				$filteringExprs = [];
 				$armCondScope = $matchScope;
 				$condNodes = [];
+				$armCondResultScope = $matchScope;
+				$bodyScope = null;
 				foreach ($arm->conds as $j => $armCond) {
 					if (isset($armCondsToSkip[$i][$j])) {
 						continue;
@@ -4453,12 +4455,17 @@ function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $context, $sto
 					if ($armCondType->isTrue()->yes()) {
 						$hasAlwaysTrueCond = true;
 					}
-					$armCondScope = $armCondResult->getScope()->filterByFalseyValue($armCondExpr);
+					$armCondScope = $armCondResultScope->filterByFalseyValue($armCondExpr);
+					if ($bodyScope === null) {
+						$bodyScope = $armCondResultScope->filterByTruthyValue($armCondExpr);
+					} else {
+						$bodyScope = $bodyScope->mergeWith($armCondResultScope->filterByTruthyValue($armCondExpr));
+					}
 					$filteringExprs[] = $armCond;
 				}
 
 				$filteringExpr = $this->getFilteringExprForMatchArm($expr, $filteringExprs);
-				$bodyScope = $matchScope->filterByTruthyValue($filteringExpr);
+				$bodyScope ??= $matchScope->filterByTruthyValue($filteringExpr);
 				$matchArmBody = new MatchExpressionArmBody($bodyScope, $arm->body);
 				$armNodes[$i] = new MatchExpressionArm($matchArmBody, $condNodes, $arm->getStartLine());
 
@@ -4475,7 +4482,7 @@ function (MutatingScope $scope) use ($stmt, $expr, $nodeCallback, $context, $sto
 				$hasYield = $hasYield || $armResult->hasYield();
 				$throwPoints = array_merge($throwPoints, $armResult->getThrowPoints());
 				$impurePoints = array_merge($impurePoints, $armResult->getImpurePoints());
-				$matchScope = $matchScope->filterByFalseyValue($filteringExpr);
+				$matchScope = $armCondScope->filterByFalseyValue($filteringExpr);
 			}
 
 			if (!$hasDefaultCond && !$hasAlwaysTrueCond && $condType->isBoolean()->yes() && $condType->isConstantScalarValue()->yes()) {

tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php

@@ -1235,6 +1235,26 @@ public function testBug10909(): void
 		$this->analyse([__DIR__ . '/data/bug-10909.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.0')]
+	public function testBug13981(): void
+	{
+		$this->cliArgumentsVariablesRegistered = true;
+		$this->polluteScopeWithLoopInitialAssignments = true;
+		$this->checkMaybeUndefinedVariables = true;
+		$this->polluteScopeWithAlwaysIterableForeach = true;
+
+		$this->analyse([__DIR__ . '/data/bug-13981.php'], [
+			[
+				'Undefined variable: $baseDir',
+				34,
+			],
+			[
+				'Variable $baseDir might not be defined.',
+				46,
+			],
+		]);
+	}
+
 	#[RequiresPhp('>= 8.0')]
 	public function testBug7705(): void
 	{

tests/PHPStan/Rules/Variables/data/bug-13981.php

@@ -0,0 +1,61 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug13981;
+
+function foo(): string
+{
+	$path = match (true) {
+		is_dir($baseDir = dirname(__DIR__).'/lang') => $baseDir,
+		default => '/translations',
+	};
+
+	return $path;
+}
+
+function foo2(): string
+{
+	if (rand(0, 1)) {
+		$baseDir = '';
+	}
+
+	$path = match (true) {
+		is_dir($baseDir = dirname(__DIR__).'/lang') => $baseDir,
+		default => '/translations',
+	};
+
+	return $path;
+}
+
+function foo3(): string
+{
+	$path = match (true) {
+		is_dir(dirname(__DIR__).'/lang2') => $baseDir,
+		is_dir($baseDir = dirname(__DIR__).'/lang') => $baseDir,
+		default => '/translations',
+	};
+
+	return $path;
+}
+
+function foo4(): string
+{
+	$path = match (true) {
+		is_dir(dirname(__DIR__).'/lang2'),
+		is_dir($baseDir = dirname(__DIR__).'/lang') => $baseDir,
+		default => '/translations',
+	};
+
+	return $path;
+}
+
+function foo5(): string
+{
+	$path = match (true) {
+		is_dir($baseDir = dirname(__DIR__).'/lang') => '$baseDir',
+		default => $baseDir,
+	};
+
+	return $path;
+}