Fix phpstan/phpstan#13853: Smarter check about ununitialized readonly properties

src/Analyser/TypeSpecifier.php

@@ -21,6 +21,7 @@
 use PhpParser\Node\Name;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Node\Expr\AlwaysRememberedExpr;
+use PHPStan\Node\Expr\PropertyInitializationExpr;
 use PHPStan\Node\Expr\TypeExpr;
 use PHPStan\Node\IssetExpr;
 use PHPStan\Node\Printer\ExprPrinter;
@@ -1028,7 +1029,21 @@ public function specifyTypesInCondition(
 					}
 				}
 
-				return new SpecifiedTypes();
+				if (
+						$issetExpr instanceof PropertyFetch
+						&& $issetExpr->var instanceof Expr\Variable
+						&& $issetExpr->var->name === 'this'
+						&& $issetExpr->name instanceof Node\Identifier
+					) {
+						return $this->create(
+							new PropertyInitializationExpr($issetExpr->name->toString()),
+							new NeverType(),
+							TypeSpecifierContext::createTrue(),
+							$scope,
+						)->setRootExpr($expr);
+				}
+
+					return new SpecifiedTypes();
 			}
 
 			$tmpVars = [$issetExpr];

src/Node/ClassPropertiesNode.php

@@ -212,7 +212,7 @@
 				if (array_key_exists($propertyName, $initializedPropertiesMap)) {
 					$hasInitialization = $initializedPropertiesMap[$propertyName];
 					if (in_array($function->getName(), $constructors, true)) {
-						$hasInitialization = $hasInitialization->or($usageScope->hasExpressionType(new PropertyInitializationExpr($propertyName)));
+						$hasInitialization = $hasInitialization->or(self::hasPropertyInitialization($usageScope, $propertyName));
 					}
 					if (
 						!$hasInitialization->no()
@@ -234,9 +234,9 @@
 				) {
 					continue;
 				}
-				$hasInitialization = $initializedPropertiesMap[$propertyName]->or($usageScope->hasExpressionType(new PropertyInitializationExpr($propertyName)));
+				$hasInitialization = $initializedPropertiesMap[$propertyName]->or(self::hasPropertyInitialization($usageScope, $propertyName));
 				if (!$hasInitialization->yes() && $usageScope->isInAnonymousFunction() && $usageScope->getParentScope() !== null) {
-					$hasInitialization = $hasInitialization->or($usageScope->getParentScope()->hasExpressionType(new PropertyInitializationExpr($propertyName)));
+					$hasInitialization = $hasInitialization->or(self::hasPropertyInitialization($usageScope->getParentScope(), $propertyName));
 				}
 				if (!$hasInitialization->yes()) {
 					$prematureAccess[] = [
@@ -304,7 +304,7 @@
 			}
 
 			foreach (array_keys($uninitializedProperties) as $propertyName) {
-				if (!$methodScope->hasExpressionType(new PropertyInitializationExpr($propertyName))->yes()) {
+				if (!self::hasPropertyInitialization($methodScope, $propertyName)->yes()) {
 					continue;
 				}
 
@@ -405,12 +405,23 @@
 	private function getInitializedProperties(Scope $scope, array $initialInitializedProperties): array
 	{
 		foreach ($initialInitializedProperties as $propertyName => $isInitialized) {
-			$initialInitializedProperties[$propertyName] = $isInitialized->or($scope->hasExpressionType(new PropertyInitializationExpr($propertyName)));
+			$initialInitializedProperties[$propertyName] = $isInitialized->or(self::hasPropertyInitialization($scope, $propertyName));
 		}
 
 		return $initialInitializedProperties;
 	}
 
+	private static function hasPropertyInitialization(Scope $scope, string $propertyName): TrinaryLogic
+	{
+		$initExpr = new PropertyInitializationExpr($propertyName);
+		$has = $scope->hasExpressionType($initExpr);
+		if ($has->yes() && $scope->getType($initExpr) instanceof NeverType) {
+			return TrinaryLogic::createNo();
+		}
+
+		return $has;
+	}
+
 	/**
 	 * @return list<PropertyAssign>
 	 */

src/Rules/IssetCheck.php

@@ -156,6 +156,7 @@ public function check(Expr $expr, Scope $scope, string $operatorDescription, str
 					&& $expr->var instanceof Expr\Variable
 					&& $expr->var->name === 'this'
 					&& $scope->hasExpressionType(new PropertyInitializationExpr($propertyReflection->getName()))->yes()
+					&& !$scope->getType(new PropertyInitializationExpr($propertyReflection->getName())) instanceof NeverType
 				) {
 					return $this->generateError(
 						$propertyReflection->getNativeType(),

src/Rules/Properties/ReadOnlyPropertyAssignRule.php

@@ -6,6 +6,7 @@
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
 use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Node\Expr\PropertyInitializationExpr;
 use PHPStan\Node\Expr\SetOffsetValueTypeExpr;
 use PHPStan\Node\Expr\UnsetOffsetExpr;
 use PHPStan\Node\PropertyAssignNode;
@@ -14,6 +15,7 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\ShouldNotHappenException;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\TypeUtils;
 use function in_array;
@@ -111,6 +113,16 @@
 				continue;
 			}
 
+			if (
+				$propertyFetch->var instanceof Node\Expr\Variable
+				&& $propertyFetch->var->name === 'this'
+				&& $propertyFetch->name instanceof Node\Identifier
+				&& $scope->hasExpressionType(new PropertyInitializationExpr($propertyFetch->name->toString()))->yes()
+				&& $scope->getType(new PropertyInitializationExpr($propertyFetch->name->toString())) instanceof NeverType
+			) {
+				continue;
+			}
+
 			$errors[] = RuleErrorBuilder::message(sprintf('Readonly property %s::$%s is assigned outside of the constructor.', $declaringClass->getDisplayName(), $propertyReflection->getName()))
 				->line($propertyFetch->name->getStartLine())
 				->identifier('property.readOnlyAssignNotInConstructor')

tests/PHPStan/Rules/Properties/ReadOnlyPropertyAssignRuleTest.php

@@ -180,4 +180,15 @@ public function testCloneWith(): void
 		$this->analyse([__DIR__ . '/data/readonly-property-assign-clone-with.php'], []);
 	}
 
+	#[RequiresPhp('>= 8.1')]
+	public function testBug13853(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-13853.php'], [
+			[
+				'Readonly property Bug13853\NoIssetGuard::$prop is assigned outside of the constructor.',
+				58,
+			],
+		]);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/bug-13853.php

@@ -0,0 +1,60 @@
+<?php // lint >= 8.1
+
+declare(strict_types = 1);
+
+namespace Bug13853;
+
+abstract class BaseReportLocator
+{
+    private readonly string $report;
+
+    public function __construct(
+        private readonly string $defaultPathname,
+    ) {
+    }
+
+    final public function locate(): string
+    {
+        if (isset($this->report)) {
+            return $this->report;
+        }
+
+        $this->report = is_file($this->defaultPathname)
+            ? $this->defaultPathname
+            : $this->lookup();
+
+        return $this->report;
+    }
+
+	public abstract function lookup(): string;
+}
+
+class AnotherExample
+{
+	private readonly int $value;
+
+	public function getValue(): int
+	{
+		if (!isset($this->value)) {
+			$this->value = $this->compute();
+		}
+
+		return $this->value;
+	}
+
+	private function compute(): int
+	{
+		return 42;
+	}
+}
+
+class NoIssetGuard
+{
+	private readonly string $prop;
+
+	public function setProp(): void
+	{
+		// no isset guard - should still report error
+		$this->prop = 'foo';
+	}
+}