Remember narrowed types from the constructor when analysing other methods

conf/config.neon

@@ -495,6 +495,7 @@ services:
 			implicitThrows: %exceptions.implicitThrows%
 			treatPhpDocTypesAsCertain: %treatPhpDocTypesAsCertain%
 			universalObjectCratesClasses: %universalObjectCratesClasses%
+			narrowMethodScopeFromConstructor: true
 
 	-
 		class: PHPStan\Analyser\ConstantResolver

src/Analyser/MutatingScope.php

@@ -294,6 +294,77 @@ public function enterDeclareStrictTypes(): self
 		);
 	}
 
+	/**
+	 * @param array<string, ExpressionTypeHolder> $currentExpressionTypes
+	 * @return array<string, ExpressionTypeHolder>
+	 */
+	private function rememberConstructorExpressions(array $currentExpressionTypes): array
+	{
+		$expressionTypes = [];
+		foreach ($currentExpressionTypes as $exprString => $expressionTypeHolder) {
+			$expr = $expressionTypeHolder->getExpr();
+			if ($expr instanceof FuncCall) {
+				if (
+					!$expr->name instanceof Name
+					|| !in_array($expr->name->name, ['class_exists', 'function_exists'], true)
+				) {
+					continue;
+				}
+			} elseif ($expr instanceof PropertyFetch) {
+				if (
+					!$expr->name instanceof Node\Identifier
+					|| !$expr->var instanceof Variable
+					|| $expr->var->name !== 'this'
+					|| !$this->phpVersion->supportsReadOnlyProperties()
+				) {
+					continue;
+				}
+
+				$propertyReflection = $this->propertyReflectionFinder->findPropertyReflectionFromNode($expr, $this);
+				if ($propertyReflection === null) {
+					continue;
+				}
+
+				$nativePropertyReflection = $propertyReflection->getNativeReflection();
+				if ($nativePropertyReflection === null || !$nativePropertyReflection->isReadOnly()) {
+						continue;
+				}
+			} elseif (!$expr instanceof ConstFetch && !$expr instanceof PropertyInitializationExpr) {
+				continue;
+			}
+
+			$expressionTypes[$exprString] = $expressionTypeHolder;
+		}
+
+		if (array_key_exists('$this', $currentExpressionTypes)) {
+			$expressionTypes['$this'] = $currentExpressionTypes['$this'];
+		}
+
+		return $expressionTypes;
+	}
+
+	public function rememberConstructorScope(): self
+	{
+		return $this->scopeFactory->create(
+			$this->context,
+			$this->isDeclareStrictTypes(),
+			$this->getFunction(),
+			$this->getNamespace(),
+			$this->rememberConstructorExpressions($this->expressionTypes),
+			$this->rememberConstructorExpressions($this->nativeExpressionTypes),
+			$this->conditionalExpressions,
+			$this->inClosureBindScopeClasses,
+			$this->anonymousFunctionReflection,
+			$this->inFirstLevelStatement,
+			[],
+			[],
+			$this->inFunctionCallsStack,
+			$this->afterExtractCall,
+			$this->parentScope,
+			$this->nativeTypesPromoted,
+		);
+	}
+
 	/** @api */
 	public function isInClass(): bool
 	{
@@ -3286,7 +3357,7 @@ public function enterFunction(
 
 	private function enterFunctionLike(
 		PhpFunctionFromParserNodeReflection $functionReflection,
-		bool $preserveThis,
+		bool $preserveConstructorScope,
 	): self
 	{
 		$parametersByName = [];
@@ -3298,6 +3369,12 @@ private function enterFunctionLike(
 		$expressionTypes = [];
 		$nativeExpressionTypes = [];
 		$conditionalTypes = [];
+
+		if ($preserveConstructorScope) {
+			$expressionTypes = $this->rememberConstructorExpressions($this->expressionTypes);
+			$nativeExpressionTypes = $this->rememberConstructorExpressions($this->nativeExpressionTypes);
+		}
+
 		foreach ($functionReflection->getParameters() as $parameter) {
 			$parameterType = $parameter->getType();
 
@@ -3348,13 +3425,6 @@ private function enterFunctionLike(
 			$nativeExpressionTypes[$parameterOriginalValueExprString] = ExpressionTypeHolder::createYes($parameterOriginalValueExpr, $nativeParameterType);
 		}
 
-		if ($preserveThis && array_key_exists('$this', $this->expressionTypes)) {
-			$expressionTypes['$this'] = $this->expressionTypes['$this'];
-		}
-		if ($preserveThis && array_key_exists('$this', $this->nativeExpressionTypes)) {
-			$nativeExpressionTypes['$this'] = $this->nativeExpressionTypes['$this'];
-		}
-
 		return $this->scopeFactory->create(
 			$this->context,
 			$this->isDeclareStrictTypes(),

src/Analyser/NodeScopeResolver.php

@@ -218,6 +218,7 @@
 use function str_starts_with;
 use function strtolower;
 use function trim;
+use function usort;
 use const PHP_VERSION_ID;
 use const SORT_NUMERIC;
 
@@ -271,6 +272,7 @@ public function __construct(
 		private readonly array $universalObjectCratesClasses,
 		private readonly bool $implicitThrows,
 		private readonly bool $treatPhpDocTypesAsCertain,
+		private readonly bool $narrowMethodScopeFromConstructor,
 	)
 	{
 		$earlyTerminatingMethodNames = [];
@@ -791,6 +793,38 @@ private function processStmtNode(
 					$classReflection,
 					$methodReflection,
 				), $methodScope);
+
+				if ($isConstructor && $this->narrowMethodScopeFromConstructor) {
+					$finalScope = null;
+
+					foreach ($executionEnds as $executionEnd) {
+						if ($executionEnd->getStatementResult()->isAlwaysTerminating()) {
+							continue;
+						}
+
+						$endScope = $executionEnd->getStatementResult()->getScope();
+						if ($finalScope === null) {
+							$finalScope = $endScope;
+							continue;
+						}
+
+						$finalScope = $finalScope->mergeWith($endScope);
+					}
+
+					foreach ($gatheredReturnStatements as $statement) {
+						if ($finalScope === null) {
+							$finalScope = $statement->getScope();
+							continue;
+						}
+
+						$finalScope = $finalScope->mergeWith($statement->getScope());
+					}
+
+					if ($finalScope !== null) {
+						$scope = $finalScope->rememberConstructorScope();
+					}
+
+				}
 			}
 		} elseif ($stmt instanceof Echo_) {
 			$hasYield = false;
@@ -925,7 +959,26 @@ private function processStmtNode(
 			$classStatementsGatherer = new ClassStatementsGatherer($classReflection, $nodeCallback);
 			$this->processAttributeGroups($stmt, $stmt->attrGroups, $classScope, $classStatementsGatherer);
 
-			$this->processStmtNodes($stmt, $stmt->stmts, $classScope, $classStatementsGatherer, $context);
+			$classLikeStatements = $stmt->stmts;
+			if ($this->narrowMethodScopeFromConstructor) {
+				// analyze static methods first; constructor next; instance methods and property hooks last so we can carry over the scope
+				usort($classLikeStatements, static function ($a, $b) {
+					if ($a instanceof Node\Stmt\Property) {
+						return 1;
+					}
+					if ($b instanceof Node\Stmt\Property) {
+						return -1;
+					}
+
+					if (!$a instanceof Node\Stmt\ClassMethod || !$b instanceof Node\Stmt\ClassMethod) {
+						return 0;
+					}
+
+					return [!$a->isStatic(), $a->name->toLowerString() !== '__construct'] <=> [!$b->isStatic(), $b->name->toLowerString() !== '__construct'];
+				});
+			}
+
+			$this->processStmtNodes($stmt, $classLikeStatements, $classScope, $classStatementsGatherer, $context);
 			$nodeCallback(new ClassPropertiesNode($stmt, $this->readWritePropertiesExtensionProvider, $classStatementsGatherer->getProperties(), $classStatementsGatherer->getPropertyUsages(), $classStatementsGatherer->getMethodCalls(), $classStatementsGatherer->getReturnStatementsNodes(), $classStatementsGatherer->getPropertyAssigns(), $classReflection), $classScope);
 			$nodeCallback(new ClassMethodsNode($stmt, $classStatementsGatherer->getMethods(), $classStatementsGatherer->getMethodCalls(), $classReflection), $classScope);
 			$nodeCallback(new ClassConstantsNode($stmt, $classStatementsGatherer->getConstants(), $classStatementsGatherer->getConstantFetches(), $classReflection), $classScope);

src/Rules/IssetCheck.php

@@ -5,6 +5,7 @@
 use PhpParser\Node;
 use PhpParser\Node\Expr;
 use PHPStan\Analyser\Scope;
+use PHPStan\Node\Expr\PropertyInitializationExpr;
 use PHPStan\Rules\Properties\PropertyDescriptor;
 use PHPStan\Rules\Properties\PropertyReflectionFinder;
 use PHPStan\Type\NeverType;
@@ -143,6 +144,27 @@ public function check(Expr $expr, Scope $scope, string $operatorDescription, str
 			}
 
 			if ($propertyReflection->hasNativeType() && !$propertyReflection->isVirtual()->yes()) {
+				if (
+					$expr instanceof Node\Expr\PropertyFetch
+					&& $expr->name instanceof Node\Identifier
+					&& $expr->var instanceof Expr\Variable
+					&& $expr->var->name === 'this'
+					&& $propertyReflection->getNativeType()->isNull()->no()
+					&& $scope->hasExpressionType(new PropertyInitializationExpr($propertyReflection->getName()))->yes()
+				) {
+					return $this->generateError(
+						$propertyReflection->getNativeType(),
+						sprintf(
+							'%s %s',
+							$this->propertyDescriptor->describeProperty($propertyReflection, $scope, $expr),
+							$operatorDescription,
+						),
+						$typeMessageCallback,
+						$identifier,
+						'propertyNeverNullOrUninitialized',
+					);
+				}
+
 				if (!$scope->hasExpressionType($expr)->yes()) {
 					if ($expr instanceof Node\Expr\PropertyFetch) {
 						return $this->checkUndefined($expr->var, $scope, $operatorDescription, $identifier);
@@ -280,7 +302,7 @@ private function checkUndefined(Expr $expr, Scope $scope, string $operatorDescri
 	/**
 	 * @param callable(Type): ?string $typeMessageCallback
 	 * @param ErrorIdentifier $identifier
-	 * @param 'variable'|'offset'|'property'|'expr' $identifierSecondPart
+	 * @param 'variable'|'offset'|'property'|'expr'|'propertyNeverNullOrUninitialized' $identifierSecondPart
 	 */
 	private function generateError(Type $type, string $message, callable $typeMessageCallback, string $identifier, string $identifierSecondPart): ?IdentifierRuleError
 	{

src/Testing/RuleTestCase.php

@@ -110,6 +110,7 @@ private function getAnalyser(DirectRuleRegistry $ruleRegistry): Analyser
 				self::getContainer()->getParameter('universalObjectCratesClasses'),
 				self::getContainer()->getParameter('exceptions')['implicitThrows'],
 				$this->shouldTreatPhpDocTypesAsCertain(),
+				$this->shouldNarrowMethodScopeFromConstructor(),
 			);
 			$fileAnalyser = new FileAnalyser(
 				$this->createScopeFactory($reflectionProvider, $typeSpecifier),
@@ -261,6 +262,11 @@ protected function shouldFailOnPhpErrors(): bool
 		return true;
 	}
 
+	protected function shouldNarrowMethodScopeFromConstructor(): bool
+	{
+		return false;
+	}
+
 	public static function getAdditionalConfigFiles(): array
 	{
 		return [

src/Testing/TypeInferenceTestCase.php

@@ -90,6 +90,7 @@ public static function processFile(
 			self::getContainer()->getParameter('universalObjectCratesClasses'),
 			self::getContainer()->getParameter('exceptions')['implicitThrows'],
 			self::getContainer()->getParameter('treatPhpDocTypesAsCertain'),
+			true,
 		);
 		$resolver->setAnalysedFiles(array_map(static fn (string $file): string => $fileHelper->normalizePath($file), array_merge([$file], static::getAdditionalAnalysedFiles())));
 

tests/PHPStan/Analyser/AnalyserTest.php

@@ -733,6 +733,7 @@ private function createAnalyser(): Analyser
 			[stdClass::class],
 			true,
 			$this->shouldTreatPhpDocTypesAsCertain(),
+			true,
 		);
 		$lexer = new Lexer();
 		$fileAnalyser = new FileAnalyser(

tests/PHPStan/Analyser/nsrt/remember-readonly-constructor-narrowed-hooks.php

@@ -0,0 +1,35 @@
+<?php // lint >= 8.4
+
+namespace RememberReadOnlyConstructorInPropertyHookBodies;
+
+use function PHPStan\Testing\assertType;
+
+class User
+{
+	public string $name {
+		get {
+			assertType('1|2', $this->type);
+			return $this->name ;
+		}
+		set {
+			if (strlen($value) === 0) {
+				throw new ValueError("Name must be non-empty");
+			}
+			assertType('1|2', $this->type);
+			$this->name = $value;
+		}
+	}
+
+	private readonly int $type;
+
+	public function __construct(
+		string $name
+	) {
+		$this->name = $name;
+		if (rand(0,1)) {
+			$this->type = 1;
+		} else {
+			$this->type = 2;
+		}
+	}
+}