fix returntype for DateIntervall::createFromDateString

conf/config.neon

@@ -1324,6 +1324,11 @@ services:
 		tags:
 			- phpstan.dynamicStaticMethodThrowTypeExtension
 
+	-
+		class: PHPStan\Type\Php\DateIntervalDynamicReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicStaticMethodReturnTypeExtension
+
 	-
 		class: PHPStan\Type\Php\DateTimeCreateDynamicReturnTypeExtension
 		tags:

resources/functionMap.php

@@ -1583,7 +1583,7 @@
 'DateInterval::__construct' => ['void', 'spec'=>'string'],
 'DateInterval::__set_state' => ['DateInterval', 'array'=>'array'],
 'DateInterval::__wakeup' => ['void'],
-'DateInterval::createFromDateString' => ['DateInterval', 'time'=>'string'],
+'DateInterval::createFromDateString' => ['DateInterval|false', 'time'=>'string'],
 'DateInterval::format' => ['string', 'format'=>'string'],
 'DatePeriod::__construct' => ['void', 'start'=>'DateTimeInterface', 'interval'=>'DateInterval', 'recur'=>'int', 'options='=>'int'],
 'DatePeriod::__construct\'1' => ['void', 'start'=>'DateTimeInterface', 'interval'=>'DateInterval', 'end'=>'DateTimeInterface', 'options='=>'int'],

src/Type/Php/DateIntervalDynamicReturnTypeExtension.php

@@ -0,0 +1,61 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use DateInterval;
+use PhpParser\Node\Expr\StaticCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\DynamicStaticMethodReturnTypeExtension;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\Type;
+use function count;
+use function in_array;
+
+class DateIntervalDynamicReturnTypeExtension
+implements DynamicStaticMethodReturnTypeExtension
+{
+
+	public function getClass(): string
+	{
+		return DateInterval::class;
+	}
+
+	public function isStaticMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return $methodReflection->getName() === 'createFromDateString';
+	}
+
+	public function getTypeFromStaticMethodCall(MethodReflection $methodReflection, StaticCall $methodCall, Scope $scope): ?Type
+	{
+		$arguments = $methodCall->getArgs();
+
+		if (!isset($arguments[0])) {
+			return null;
+		}
+
+		$strings = $scope->getType($arguments[0]->value)->getConstantStrings();
+
+		$possibleReturnTypes = [];
+		foreach ($strings as $string) {
+			$possibleReturnTypes[] = @DateInterval::createFromDateString($string->getValue()) instanceof DateInterval ? DateInterval::class : false;
+		}
+
+		// the error case, when wrong types are passed
+		if (count($possibleReturnTypes) === 0) {
+			return null;
+		}
+
+		if (in_array(false, $possibleReturnTypes, true) && in_array(DateInterval::class, $possibleReturnTypes, true)) {
+			return null;
+		}
+
+		if (in_array(false, $possibleReturnTypes, true)) {
+			return new ConstantBooleanType(false);
+		}
+
+		return new ObjectType(DateInterval::class);
+	}
+
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1136,6 +1136,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/imagick-pixel.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/Arrays/data/bug-8467a.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8467b.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8442.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/PDOStatement.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/discussion-8447.php');
 	}

tests/PHPStan/Analyser/data/bug-8442.php

@@ -0,0 +1,41 @@
+<?php declare(strict_types = 1);
+
+namespace Bug8442;
+
+use stdClass;
+use function PHPStan\Testing\assertType;
+use DateInterval;
+
+function () {
+	assertType('false', DateInterval::createFromDateString('foo'));
+	assertType('DateInterval', DateInterval::createFromDateString('1 Day'));
+
+	if (rand(0,1)) {
+		$interval = '1 day';
+	} else {
+		$interval = '2 day';
+	}
+
+	assertType('DateInterval', DateInterval::createFromDateString($interval));
+
+	if (rand(0,1)) {
+		$interval = 'foo';
+	} else {
+		$interval = '2 day';
+	}
+
+	assertType('DateInterval|false', DateInterval::createFromDateString($interval));
+
+	if (rand(0,1)) {
+		$interval = 'foo';
+	} else {
+		$interval = 'foo';
+	}
+
+	assertType('false', DateInterval::createFromDateString($interval));
+
+	assertType('DateInterval|false',DateInterval::createFromDateString(str_shuffle('1 day')));
+	assertType('DateInterval|false',DateInterval::createFromDateString());
+	assertType('DateInterval|false',DateInterval::createFromDateString(new stdClass()));
+};
+