Add DateTimeSubMethodThrowTypeExtension

conf/config.neon

@@ -1421,6 +1421,11 @@ services:
 		tags:
 			- phpstan.dynamicMethodThrowTypeExtension
 
+	-
+		class: PHPStan\Type\Php\DateTimeSubMethodThrowTypeExtension
+		tags:
+			- phpstan.dynamicMethodThrowTypeExtension
+
 	-
 		class: PHPStan\Type\Php\DateTimeZoneConstructorThrowTypeExtension
 		tags:

src/Type/Php/DateTimeSubMethodThrowTypeExtension.php

@@ -0,0 +1,43 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use DateTime;
+use DateTimeImmutable;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Type\DynamicMethodThrowTypeExtension;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\Type;
+use function count;
+use function in_array;
+
+final class DateTimeSubMethodThrowTypeExtension implements DynamicMethodThrowTypeExtension
+{
+
+	public function __construct(private PhpVersion $phpVersion)
+	{
+	}
+
+	public function isMethodSupported(MethodReflection $methodReflection): bool
+	{
+		return $methodReflection->getName() === 'sub'
+			&& in_array($methodReflection->getDeclaringClass()->getName(), [DateTime::class, DateTimeImmutable::class], true);
+	}
+
+	public function getThrowTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): ?Type
+	{
+		if (count($methodCall->getArgs()) === 0) {
+			return null;
+		}
+
+		if (!$this->phpVersion->hasDateTimeExceptions()) {
+			return null;
+		}
+
+		return new ObjectType('DateMalformedStringException');
+	}
+
+}

tests/PHPStan/Rules/Methods/CallToMethodStatementWithoutSideEffectsRuleTest.php

@@ -5,6 +5,8 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Testing\RuleTestCase;
+use function array_merge;
+use const PHP_VERSION_ID;
 
 /**
  * @extends RuleTestCase<CallToMethodStatementWithoutSideEffectsRule>
@@ -89,6 +91,26 @@ public function testBug4455(): void
 		$this->analyse([__DIR__ . '/data/bug-4455.php'], []);
 	}
 
+	public function testBug11503(): void
+	{
+		$errors = [
+			['Call to method DateTimeImmutable::add() on a separate line has no effect.', 10],
+			['Call to method DateTimeImmutable::modify() on a separate line has no effect.', 11],
+			['Call to method DateTimeImmutable::setDate() on a separate line has no effect.', 12],
+			['Call to method DateTimeImmutable::setISODate() on a separate line has no effect.', 13],
+			['Call to method DateTimeImmutable::setTime() on a separate line has no effect.', 14],
+			['Call to method DateTimeImmutable::setTimestamp() on a separate line has no effect.', 15],
+			['Call to method DateTimeImmutable::setTimezone() on a separate line has no effect.', 17],
+		];
+		if (PHP_VERSION_ID < 80300) {
+			$errors = array_merge([
+				['Call to method DateTimeImmutable::sub() on a separate line has no effect.', 9],
+			], $errors);
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-11503.php'], $errors);
+	}
+
 	public function testFirstClassCallables(): void
 	{
 		$this->analyse([__DIR__ . '/data/first-class-callable-method-without-side-effect.php'], [

tests/PHPStan/Rules/Methods/data/bug-11503.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Bug11503;
+
+class Foo {
+	public function test() {
+		$date = new \DateTimeImmutable();
+		$interval = new \DateInterval('P1M');
+		$date->sub($interval);
+		$date->add($interval);
+		$date->modify('+1 day');
+		$date->setDate(2024, 8, 13);
+		$date->setISODate(2024, 1);
+		$date->setTime(0, 0, 0, 0);
+		$date->setTimestamp(1);
+		$zone = new \DateTimeZone('UTC');
+		$date->setTimezone($zone);
+	}
+}