From 032b135e48d5673cdce1e39bbd22c26180c26805 Mon Sep 17 00:00:00 2001
From: Daniel Lee <bearlee@alum.mit.edu>
Date: Thu, 14 Dec 2023 21:17:57 -0500
Subject: [PATCH] adding back in a require trait that is used by Stan

---
 stan/math/prim/meta/is_kernel_expression.hpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/stan/math/prim/meta/is_kernel_expression.hpp b/stan/math/prim/meta/is_kernel_expression.hpp
index 940b4ae5a8f..574df21c2f2 100644
--- a/stan/math/prim/meta/is_kernel_expression.hpp
+++ b/stan/math/prim/meta/is_kernel_expression.hpp
@@ -112,6 +112,10 @@ using require_kernel_expression_lhs_t
 
 // STAN_ADD_REQUIRE_UNARY(rev_kernel_expression, is_rev_kernel_expression,
 // opencl_kernel_generator);
+template <typename T>
+using require_rev_kernel_expression_t
+    = require_t<is_rev_kernel_expression<std::decay_t<T>>>;
+  
 //  STAN_ADD_REQUIRE_UNARY(prim_or_rev_kernel_expression,
 //  is_prim_or_rev_kernel_expression, opencl_kernel_generator);
 template <typename... Types>