Describe Traversable

Author: VincentLanglet

src/Type/ObjectType.php

@@ -5,11 +5,6 @@
 use ArrayAccess;
 use Closure;
 use Countable;
-use DateTime;
-use DateTimeImmutable;
-use DateTimeInterface;
-use Error;
-use Exception;
 use Iterator;
 use IteratorAggregate;
 use PHPStan\Analyser\OutOfClassScope;
@@ -1560,23 +1555,16 @@ private function getInterfaces(): array
 
 	public function tryRemove(Type $typeToRemove): ?Type
 	{
-		if ($this->getClassName() === DateTimeInterface::class) {
-			if ($typeToRemove instanceof ObjectType && $typeToRemove->getClassName() === DateTimeImmutable::class) {
-				return new ObjectType(DateTime::class);
-			}
-
-			if ($typeToRemove instanceof ObjectType && $typeToRemove->getClassName() === DateTime::class) {
-				return new ObjectType(DateTimeImmutable::class);
-			}
-		}
-
-		if ($this->getClassName() === Throwable::class) {
-			if ($typeToRemove instanceof ObjectType && $typeToRemove->getClassName() === Error::class) {
-				return new ObjectType(Exception::class); // phpcs:ignore SlevomatCodingStandard.Exceptions.ReferenceThrowableOnly.ReferencedGeneralException
-			}
-
-			if ($typeToRemove instanceof ObjectType && $typeToRemove->getClassName() === Exception::class) { // phpcs:ignore SlevomatCodingStandard.Exceptions.ReferenceThrowableOnly.ReferencedGeneralException
-				return new ObjectType(Error::class);
+		foreach (UnionType::EQUAL_UNION_CLASSES as $baseClass => $classes) {
+			if ($this->getClassName() === $baseClass && $typeToRemove instanceof ObjectType) {
+				foreach ($classes as $index => $class) {
+					if ($typeToRemove->getClassName() === $class) {
+						unset($classes[$index]);
+						return TypeCombinator::union(
+							...array_map(static fn (string $objectClass): Type => new ObjectType($objectClass), $classes)
+						);
+					}
+				}
 			}
 		}
 

src/Type/UnionType.php

@@ -5,6 +5,10 @@
 use DateTime;
 use DateTimeImmutable;
 use DateTimeInterface;
+use Error;
+use Exception;
+use Iterator;
+use IteratorAggregate;
 use PHPStan\Php\PhpVersion;
 use PHPStan\PhpDocParser\Ast\Type\TypeNode;
 use PHPStan\PhpDocParser\Ast\Type\UnionTypeNode;
@@ -26,6 +30,8 @@
 use PHPStan\Type\Generic\TemplateTypeVariance;
 use PHPStan\Type\Generic\TemplateUnionType;
 use PHPStan\Type\Traits\NonGeneralizableTypeTrait;
+use Throwable;
+use Traversable;
 use function array_diff_assoc;
 use function array_fill_keys;
 use function array_map;
@@ -45,6 +51,12 @@ class UnionType implements CompoundType
 
 	use NonGeneralizableTypeTrait;
 
+	public const EQUAL_UNION_CLASSES = [
+		DateTimeInterface::class => [DateTimeImmutable::class, DateTime::class],
+		Throwable::class => [Error::class, Exception::class],
+		Traversable::class => [IteratorAggregate::class, Iterator::class],
+	];
+
 	private bool $sortedTypes = false;
 
 	/** @var array<int, string> */
@@ -183,14 +195,15 @@ public function getConstantStrings(): array
 
 	public function accepts(Type $type, bool $strictTypes): AcceptsResult
 	{
-		if (
-			$type->equals(new ObjectType(DateTimeInterface::class))
-			&& $this->accepts(
-				new UnionType([new ObjectType(DateTime::class), new ObjectType(DateTimeImmutable::class)]),
-				$strictTypes,
-			)->yes()
-		) {
-			return AcceptsResult::createYes();
+		foreach (self::EQUAL_UNION_CLASSES as $baseClass => $classes) {
+			if ($type->equals(new ObjectType($baseClass))) {
+				$union = TypeCombinator::union(
+					...array_map(static fn (string $objectClass): Type => new ObjectType($objectClass), $classes)
+				);
+				if ($this->accepts($union, $strictTypes)->yes()) {
+					return AcceptsResult::createYes();
+				}
+			}
 		}
 
 		$result = AcceptsResult::createNo();

tests/PHPStan/Rules/Methods/ReturnTypeRuleTest.php

@@ -1096,4 +1096,9 @@ public function testBug11857(): void
 		$this->analyse([__DIR__ . '/data/bug-11857-builder.php'], []);
 	}
 
+	public function testBug12102(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12102.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/bug-12102.php

@@ -0,0 +1,34 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12102;
+
+use Iterator;
+use IteratorAggregate;
+use Traversable;
+
+class HelloWorld
+{
+	/** @param Traversable<mixed, mixed> $traversable */
+	public function sayHello(Traversable $traversable): ?Iterator
+	{
+		if (!$traversable instanceof IteratorAggregate) {
+			return $traversable;
+		}
+
+		return null;
+	}
+
+	/** @param iterable<mixed, mixed> $iterable */
+	public function sayHello2(iterable $iterable): ?Iterator
+	{
+		if (\is_array($iterable)) {
+			return null;
+		}
+
+		if (!$iterable instanceof IteratorAggregate) {
+			return $iterable;
+		}
+
+		return null;
+	}
+}