From 4c5ded8c849de94f3d2d2d6e6f4e6e0605d7e3be Mon Sep 17 00:00:00 2001
From: Zhihao Yuan <lichray@gmail.com>
Date: Sun, 17 Nov 2019 18:55:52 -0600
Subject: [PATCH] Constrain Argument constructor better

Without this change, std::allocator can construct Argument
---
 include/argparse.hpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/argparse.hpp b/include/argparse.hpp
index d06ec35..4498462 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -69,6 +69,11 @@ struct is_container<
 template <typename T>
 static constexpr bool is_container_v = is_container<T>::value;
 
+template <typename T>
+struct is_string_like
+    : std::conjunction<std::is_constructible<std::string, T>,
+                       std::is_convertible<T, std::string_view>> {};
+
 template <typename T>
 using enable_if_container = std::enable_if_t<is_container_v<T>, T>;
 
@@ -115,8 +120,7 @@ public:
 
   template <typename... Args,
             std::enable_if_t<
-                std::conjunction_v<std::is_constructible<std::string, Args>...>,
-                int> = 0>
+                std::conjunction_v<details::is_string_like<Args>...>, int> = 0>
   explicit Argument(Args &&... args)
       : Argument({std::string(std::forward<Args>(args))...},
                  std::make_index_sequence<sizeof...(Args)>{}) {}