Fix DatePeriod constructor extension in subclasses

src/Type/Php/DatePeriodConstructorReturnTypeExtension.php

@@ -6,6 +6,7 @@
 use DateTime;
 use DateTimeInterface;
 use PhpParser\Node\Expr\StaticCall;
+use PhpParser\Node\Name;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\MethodReflection;
 use PHPStan\Type\DynamicStaticMethodReturnTypeExtension;
@@ -15,6 +16,7 @@
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\StringType;
 use PHPStan\Type\Type;
+use function strtolower;
 
 class DatePeriodConstructorReturnTypeExtension implements DynamicStaticMethodReturnTypeExtension
 {
@@ -35,6 +37,15 @@ public function getTypeFromStaticMethodCall(MethodReflection $methodReflection,
 			return new ObjectType(DatePeriod::class);
 		}
 
+		if (!$methodCall->class instanceof Name) {
+			return new ObjectType(DatePeriod::class);
+		}
+
+		$className = $scope->resolveName($methodCall->class);
+		if (strtolower($className) !== 'dateperiod') {
+			return new ObjectType($className);
+		}
+
 		$firstArgType = $scope->getType($methodCall->getArgs()[0]->value);
 		if ((new StringType())->isSuperTypeOf($firstArgType)->yes()) {
 			$firstArgType = new ObjectType(DateTime::class);

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -678,6 +678,8 @@ public function dataFileAsserts(): iterable
 		} else {
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/hash-functions-74.php');
 		}
+
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6500.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-6500.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Bug6500;
+
+use function PHPStan\Testing\assertType;
+
+class DatePeriodExample extends \DatePeriod {
+
+	public static function test(): void {
+		$self = new self(new \DateTimeImmutable('2022-01-01'), new \DateInterval('P1M'), new \DateTimeImmutable('2022-01-31'));
+		assertType(self::class, $self);
+	}
+
+}