These DateTimeInterface methods are pure

Author: ondrejmirtes

bin/functionMetadata_original.php

@@ -130,6 +130,12 @@
 	'random_int' => ['hasSideEffects' => true],
 
 	// methods
+	'DateTimeInterface::diff' => ['hasSideEffects' => false],
+	'DateTimeInterface::format' => ['hasSideEffects' => false],
+	'DateTimeInterface::getOffset' => ['hasSideEffects' => false],
+	'DateTimeInterface::getTimestamp' => ['hasSideEffects' => false],
+	'DateTimeInterface::getTimezone' => ['hasSideEffects' => false],
+
 	'DateTime::createFromFormat' => ['hasSideEffects' => false],
 	'DateTime::createFromImmutable' => ['hasSideEffects' => false],
 	'DateTime::getLastErrors' => ['hasSideEffects' => false],

resources/functionMetadata.php

@@ -86,6 +86,11 @@
 	'DateTimeImmutable::setTimestamp' => ['hasSideEffects' => false],
 	'DateTimeImmutable::setTimezone' => ['hasSideEffects' => false],
 	'DateTimeImmutable::sub' => ['hasSideEffects' => false],
+	'DateTimeInterface::diff' => ['hasSideEffects' => false],
+	'DateTimeInterface::format' => ['hasSideEffects' => false],
+	'DateTimeInterface::getOffset' => ['hasSideEffects' => false],
+	'DateTimeInterface::getTimestamp' => ['hasSideEffects' => false],
+	'DateTimeInterface::getTimezone' => ['hasSideEffects' => false],
 	'Error::__construct' => ['hasSideEffects' => false],
 	'ErrorException::__construct' => ['hasSideEffects' => false],
 	'Event::__construct' => ['hasSideEffects' => false],

tests/PHPStan/Rules/Pure/data/pure-method.php

@@ -421,3 +421,32 @@ public static function getB(): int
 		return 1;
 	}
 }
+
+class CallDateTime
+{
+
+	/**
+	 * @phpstan-pure
+	 */
+	public function doFoo(\DateTimeInterface $date): string
+	{
+		return $date->format('j. n. Y');
+	}
+
+	/**
+	 * @phpstan-pure
+	 */
+	public function doFoo2(\DateTime $date): string
+	{
+		return $date->format('j. n. Y');
+	}
+
+	/**
+	 * @phpstan-pure
+	 */
+	public function doFoo3(\DateTimeImmutable $date): string
+	{
+		return $date->format('j. n. Y');
+	}
+
+}