Fix generalizing types in loops

ondrejmirtes · ondrejmirtes · commit c09be9ec0e8c · 2023-08-20T10:12:09.000+02:00
diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
@@ -4657,10 +4657,10 @@ private static function generalizeType(Type $a, Type $b, int $depth): Type
 			TypeUtils::getAccessoryTypes($a),
 		);
 
-		return TypeCombinator::intersect(
+		return TypeCombinator::union(TypeCombinator::intersect(
 			TypeCombinator::union(...$resultTypes, ...$otherTypes),
 			...$accessoryTypes,
-		);
+		), ...$otherTypes);
 	}
 
 	private static function getArrayDepth(Type $type): int
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -227,6 +227,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2378.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6294.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-2580.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-9753.php');
 
 		if (PHP_VERSION_ID >= 80000) {
 			yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-9721.php');
diff --git a/tests/PHPStan/Analyser/data/bug-9753.php b/tests/PHPStan/Analyser/data/bug-9753.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Bug9753;
+
+use function PHPStan\Testing\assertType;
+
+function (): void {
+	$items = [];
+	$array = [1,2,3,4,5];
+
+	foreach ($array as $entry) {
+		assertType('list<1|2|3|4|5>|null', $items);
+		if (isset($items)) {
+			if (count($items) > 2) {
+				$items = null;
+			} else {
+				$items[] = $entry;
+			}
+		}
+		assertType('list<1|2|3|4|5>|null', $items);
+	}
+
+	assertType('list<1|2|3|4|5>|null', $items);
+};
