Use exception

src/Reflection/ClassReflection.php

@@ -27,6 +27,7 @@
 use PHPStan\Reflection\Php\PhpClassReflectionExtension;
 use PHPStan\Reflection\Php\PhpPropertyReflection;
 use PHPStan\ShouldNotHappenException;
+use PHPStan\Type\CircularClassReflectionResolutionException;
 use PHPStan\Type\CircularTypeAliasDefinitionException;
 use PHPStan\Type\Constant\ConstantIntegerType;
 use PHPStan\Type\ErrorType;
@@ -193,7 +194,11 @@ public function getParentClass(): ?ClassReflection
 			return $this->cachedParentClass = null;
 		}
 
-		$extendsTag = $this->getFirstExtendsTag();
+		try {
+			$extendsTag = $this->getFirstExtendsTag();
+		} catch (CircularClassReflectionResolutionException) {
+			return $this->reflectionProvider->getClass($parentClass->getName());
+		}
 
 		if ($extendsTag !== null && $this->isValidAncestorType($extendsTag->getType(), [$parentClass->getName()])) {
 			$extendedType = $extendsTag->getType();
@@ -1349,16 +1354,17 @@ private function getFirstExtendsTag(): ?ExtendsTag
 	/** @return array<string, ExtendsTag> */
 	public function getExtendsTags(): array
 	{
-		if (isset(self::$resolvingExtendsTag[$this->getName()])) {
-			return [];
-		}
-		self::$resolvingExtendsTag[$this->getName()] = true;
-
 		$resolvedPhpDoc = $this->getResolvedPhpDoc();
 		if ($resolvedPhpDoc === null) {
 			return [];
 		}
 
+		// prevent circular reference
+		if (isset(self::$resolvingExtendsTag[$this->getName()])) {
+			throw new CircularClassReflectionResolutionException();
+		}
+		self::$resolvingExtendsTag[$this->getName()] = true;
+
 		$extendTags = $resolvedPhpDoc->getExtendsTags();
 
 		unset(self::$resolvingExtendsTag[$this->getName()]);

src/Type/CircularClassReflectionResolutionException.php

@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type;
+
+use Exception;
+
+class CircularClassReflectionResolutionException extends Exception
+{
+
+}