Fix ?parent in return type

src/Analyser/MutatingScope.php

@@ -3322,7 +3322,7 @@ public function getFunctionType($type, bool $isNullable, bool $isVariadic): Type
 			}
 		}
 
-		return ParserNodeTypeToPHPStanType::resolve($type, $this->isInClass() ? $this->getClassReflection()->getName() : null);
+		return ParserNodeTypeToPHPStanType::resolve($type, $this->isInClass() ? $this->getClassReflection() : null);
 	}
 
 	public function enterForeach(Expr $iteratee, string $valueName, ?string $keyName): self

src/Rules/Properties/OverridingPropertyRule.php

@@ -123,7 +123,7 @@ public function processNode(Node $node, Scope $scope): array
 					$prototype->getNativeType()->describe(VerbosityLevel::typeOnly())
 				))->nonIgnorable()->build();
 			} else {
-				$nativeType = ParserNodeTypeToPHPStanType::resolve($node->getNativeType(), $scope->getClassReflection()->getName());
+				$nativeType = ParserNodeTypeToPHPStanType::resolve($node->getNativeType(), $scope->getClassReflection());
 				if (!$prototype->getNativeType()->equals($nativeType)) {
 					$typeErrors[] = RuleErrorBuilder::message(sprintf(
 						'Type %s of property %s::$%s is not the same as type %s of overridden property %s::$%s.',
@@ -141,7 +141,7 @@ public function processNode(Node $node, Scope $scope): array
 				'Property %s::$%s (%s) overriding property %s::$%s should not have a native type.',
 				$classReflection->getDisplayName(),
 				$node->getName(),
-				ParserNodeTypeToPHPStanType::resolve($node->getNativeType(), $scope->getClassReflection()->getName())->describe(VerbosityLevel::typeOnly()),
+				ParserNodeTypeToPHPStanType::resolve($node->getNativeType(), $scope->getClassReflection())->describe(VerbosityLevel::typeOnly()),
 				$prototype->getDeclaringClass()->getDisplayName(),
 				$node->getName()
 			))->nonIgnorable()->build();

src/Type/ParserNodeTypeToPHPStanType.php

@@ -4,29 +4,32 @@
 
 use PhpParser\Node\Name;
 use PhpParser\Node\NullableType;
+use PHPStan\Reflection\ClassReflection;
 use PHPStan\Type\Constant\ConstantBooleanType;
 
 class ParserNodeTypeToPHPStanType
 {
 
 	/**
 	 * @param \PhpParser\Node\Name|\PhpParser\Node\Identifier|\PhpParser\Node\NullableType|\PhpParser\Node\UnionType|null $type
-	 * @param string|null $className
+	 * @param ClassReflection|null $classReflection
 	 * @return Type
 	 */
-	public static function resolve($type, ?string $className): Type
+	public static function resolve($type, ?ClassReflection $classReflection): Type
 	{
 		if ($type === null) {
 			return new MixedType();
 		} elseif ($type instanceof Name) {
 			$typeClassName = (string) $type;
 			$lowercasedClassName = strtolower($typeClassName);
-			if ($className !== null && in_array($lowercasedClassName, ['self', 'static'], true)) {
-				$typeClassName = $className;
+			if ($classReflection !== null && in_array($lowercasedClassName, ['self', 'static'], true)) {
+				$typeClassName = $classReflection->getName();
 			} elseif (
 				$lowercasedClassName === 'parent'
+				&& $classReflection !== null
+				&& $classReflection->getParentClass() !== false
 			) {
-				throw new \PHPStan\ShouldNotHappenException('parent type is not supported here');
+				$typeClassName = $classReflection->getParentClass()->getName();
 			}
 
 			if ($lowercasedClassName === 'static') {
@@ -35,11 +38,11 @@ public static function resolve($type, ?string $className): Type
 
 			return new ObjectType($typeClassName);
 		} elseif ($type instanceof NullableType) {
-			return TypeCombinator::addNull(self::resolve($type->type, $className));
+			return TypeCombinator::addNull(self::resolve($type->type, $classReflection));
 		} elseif ($type instanceof \PhpParser\Node\UnionType) {
 			$types = [];
 			foreach ($type->types as $unionTypeType) {
-				$types[] = self::resolve($unionTypeType, $className);
+				$types[] = self::resolve($unionTypeType, $classReflection);
 			}
 
 			return TypeCombinator::union(...$types);

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -426,6 +426,12 @@ public function testBug5231Two(): void
 		$this->assertNotEmpty($errors);
 	}
 
+	public function testBug5529(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-5529.php');
+		$this->assertCount(0, $errors);
+	}
+
 	/**
 	 * @param string $file
 	 * @return \PHPStan\Analyser\Error[]

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -477,6 +477,8 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/literal-string.php');
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/filter-var-returns-non-empty-string.php');
+
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-5529.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-5529.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Bug5529;
+
+use function PHPStan\Testing\assertType;
+
+class ParentClass
+{}
+
+class HelloWorld extends ParentClass
+{
+	public function run(): ?parent
+	{
+		if (rand(0,1)) {
+			return $this;
+		}
+
+		return null;
+	}
+}
+
+function (HelloWorld $hw): void {
+	assertType(ParentClass::class . '|null', $hw->run());
+};