From aed09c41b6ea3d58ddb27e65fcfd5b781b8b3dcd Mon Sep 17 00:00:00 2001
From: Alberto La Rocca <alberto@tsdb2.com>
Date: Fri, 13 Dec 2024 16:56:28 +0100
Subject: [PATCH] Fix SFINAE on `gsl::owner`. (#1174)

`std::enable_if_t` must not be used as a default template argument, otherwise the instantiator will be able to override it freely with something that doesn't fail substitution. Instead, `std::enable_if_t` itself must be the type of the template argument.

More information in the examples here: https://en.cppreference.com/w/cpp/types/enable_if
---
 include/gsl/pointers | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/gsl/pointers b/include/gsl/pointers
index 63e193e9..dd0f0682 100644
--- a/include/gsl/pointers
+++ b/include/gsl/pointers
@@ -75,7 +75,7 @@ using std::unique_ptr;
 // T must be a pointer type
 // - disallow construction from any type other than pointer type
 //
-template <class T, class = std::enable_if_t<std::is_pointer<T>::value>>
+template <class T, std::enable_if_t<std::is_pointer<T>::value, bool> = true>
 using owner = T;
 
 //