---
layout: docs
title: Facebook\HackCodegen\_Private\C\coalescevax
id: function.Facebook.HackCodegen._Private.C.coalescevax
docid: function.Facebook.HackCodegen._Private.C.coalescevax
permalink: /docs/reference/function.Facebook.HackCodegen._Private.C.coalescevax/
---
# Facebook\\HackCodegen\\_Private\\C\\coalescevax()




Return the first non-null parameter, or throw an exception if there are
none




``` Hack
namespace Facebook\HackCodegen\_Private\C;

function coalescevax<\T>(
  ?\T ...$in,
): \T;
```




## Parameters




* ` ?\T ...$in `




## Returns




- ` \T `