Add DateTimeModifyReturnTypeExtension

conf/config.neon

@@ -1193,6 +1193,20 @@ services:
 		tags:
 			- phpstan.broker.dynamicFunctionReturnTypeExtension
 
+	-
+		class: PHPStan\Type\Php\DateTimeModifyReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicMethodReturnTypeExtension
+		arguments:
+			dateTimeClass: DateTime
+
+	-
+		class: PHPStan\Type\Php\DateTimeModifyReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicMethodReturnTypeExtension
+		arguments:
+			dateTimeClass: DateTimeImmutable
+
 	-
 		class: PHPStan\Type\Php\DateTimeConstructorThrowTypeExtension
 		tags:

resources/functionMap.php

@@ -1604,7 +1604,7 @@
 'DateTime::getOffset' => ['int'],
 'DateTime::getTimestamp' => ['int'],
 'DateTime::getTimezone' => ['DateTimeZone'],
-'DateTime::modify' => ['static', 'modify'=>'string'],
+'DateTime::modify' => ['static|false', 'modify'=>'string'],
 'DateTime::setDate' => ['static', 'year'=>'int', 'month'=>'int', 'day'=>'int'],
 'DateTime::setISODate' => ['static', 'year'=>'int', 'week'=>'int', 'day='=>'int'],
 'DateTime::setTime' => ['static', 'hour'=>'int', 'minute'=>'int', 'second='=>'int', 'microseconds='=>'int'],
@@ -1623,7 +1623,7 @@
 'DateTimeImmutable::getOffset' => ['int'],
 'DateTimeImmutable::getTimestamp' => ['int'],
 'DateTimeImmutable::getTimezone' => ['DateTimeZone'],
-'DateTimeImmutable::modify' => ['static', 'modify'=>'string'],
+'DateTimeImmutable::modify' => ['static|false', 'modify'=>'string'],
 'DateTimeImmutable::setDate' => ['static', 'year'=>'int', 'month'=>'int', 'day'=>'int'],
 'DateTimeImmutable::setISODate' => ['static', 'year'=>'int', 'week'=>'int', 'day='=>'int'],
 'DateTimeImmutable::setTime' => ['static', 'hour'=>'int', 'minute'=>'int', 'second='=>'int', 'microseconds='=>'int'],

src/Type/Php/DateTimeModifyReturnTypeExtension.php

@@ -0,0 +1,79 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use DateTime;
+use DateTimeInterface;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\NeverType;
+use PHPStan\Type\StaticType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeUtils;
+use function count;
+
+class DateTimeModifyReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+
+	/** @var class-string<DateTimeInterface> */
+	private $dateTimeClass;
+
+	/** @param class-string<DateTimeInterface> $dateTimeClass */
+	public function __construct(string $dateTimeClass = DateTime::class)
+	{
+		$this->dateTimeClass = $dateTimeClass;
+	}
+
+	public function getClass(): string
+	{
+		return $this->dateTimeClass;
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return $methodReflection->getName() === 'modify';
+	}
+
+	public function getTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): Type
+	{
+		$defaultReturnType = ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+		if (count($methodCall->getArgs()) < 1) {
+			return $defaultReturnType;
+		}
+
+		$valueType = $scope->getType($methodCall->getArgs()[0]->value);
+		$constantStrings = TypeUtils::getConstantStrings($valueType);
+
+		$hasFalse = false;
+		$hasDateTime = false;
+
+		foreach ($constantStrings as $constantString) {
+			if (@(new DateTime())->modify($constantString->getValue()) === false) {
+				$hasFalse = true;
+			} else {
+				$hasDateTime = true;
+			}
+
+			$valueType = TypeCombinator::remove($valueType, $constantString);
+		}
+
+		if (!$valueType instanceof NeverType) {
+			return $defaultReturnType;
+		}
+
+		if ($hasFalse && !$hasDateTime) {
+			return new ConstantBooleanType(false);
+		}
+		if ($hasDateTime && !$hasFalse) {
+			return new StaticType($methodReflection->getDeclaringClass());
+		}
+
+		return $defaultReturnType;
+	}
+
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -435,6 +435,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2906.php');
 
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/DateTimeDynamicReturnTypes.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/DateTimeModifyReturnTypes.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4821.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4838.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-4879.php');

tests/PHPStan/Analyser/data/DateTimeModifyReturnTypes.php

@@ -0,0 +1,39 @@
+<?php declare(strict_types = 1);
+
+namespace DateTimeModifyReturnTypes;
+
+use DateTime;
+use DateTimeImmutable;
+
+class Foo
+{
+	public function modify(DateTime $datetime, DateTimeImmutable $dateTimeImmutable, string $modify): void {
+		assertType('DateTime|false', $datetime->modify($modify));
+		assertType('DateTimeImmutable|false', $dateTimeImmutable->modify($modify));
+	}
+
+	/**
+	 * @param '+1 day'|'+2 day' $modify
+	 */
+	public function modifyWithValidConstant(DateTime $datetime, DateTimeImmutable $dateTimeImmutable, string $modify): void {
+		assertType('DateTime', $datetime->modify($modify));
+		assertType('DateTimeImmutable', $dateTimeImmutable->modify($modify));
+	}
+
+	/**
+	 * @param 'kewk'|'koko' $modify
+	 */
+	public function modifyWithInvalidConstant(DateTime $datetime, DateTimeImmutable $dateTimeImmutable, string $modify): void {
+		assertType('false', $datetime->modify($modify));
+		assertType('false', $dateTimeImmutable->modify($modify));
+	}
+
+	/**
+	 * @param '+1 day'|'koko' $modify
+	 */
+	public function modifyWithBothConstant(DateTime $datetime, DateTimeImmutable $dateTimeImmutable, string $modify): void {
+		assertType('DateTime|false', $datetime->modify($modify));
+		assertType('DateTimeImmutable|false', $dateTimeImmutable->modify($modify));
+	}
+
+}