Make @param-out work even if it is the only conditional type in a function signature

Author: ondrejmirtes

src/Reflection/ParametersAcceptorSelector.php

@@ -267,6 +267,14 @@ private static function hasAcceptorTemplateOrLateResolvableType(ParametersAccept
 		}
 
 		foreach ($acceptor->getParameters() as $parameter) {
+			if (
+				$parameter instanceof ParameterReflectionWithPhpDocs
+				&& $parameter->getOutType() !== null
+				&& self::hasTemplateOrLateResolvableType($parameter->getOutType())
+			) {
+				return true;
+			}
+
 			if (!self::hasTemplateOrLateResolvableType($parameter->getType())) {
 				continue;
 			}

tests/PHPStan/Analyser/data/bug-10699.php

@@ -28,3 +28,22 @@ function (): void {
 	assertType('20', $res);
 	assertType('20', $out);
 };
+
+/**
+ * @param int $flags
+ * @param mixed $out
+ *
+ * @param-out ($flags is 2 ? 20 : 10) $out
+ */
+function test2(int $flags, &$out): void
+{
+	$out = $flags === 2 ? 20 : 10;
+}
+
+function (): void {
+	test2(1, $out);
+	assertType('10', $out);
+
+	test2(2, $out);
+	assertType('20', $out);
+};