From 3d28dd096e4b02149601dc371a2b1c14079625b2 Mon Sep 17 00:00:00 2001
From: Yuriy Chernyshov <thegeorg@yandex-team.ru>
Date: Fri, 5 Aug 2022 16:22:09 +0300
Subject: [PATCH] Fix -Wignored-reference-qualifiers

In certain STLs, `std::vector<bool>::reference` is just `bool&`.
Prepending `const` causes the following warning:
```
include/nlohmann/detail/conversions/to_json.hpp:271:42: error: 'const' qualifier on reference type 'std::vector<bool>::reference' (aka 'bool &') has no effect [-Werror,-Wignored-reference-qualifiers]
```

This PR fixes the problem.
---
 include/nlohmann/detail/conversions/to_json.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
index ba24c118d..52ddaddef 100644
--- a/include/nlohmann/detail/conversions/to_json.hpp
+++ b/include/nlohmann/detail/conversions/to_json.hpp
@@ -268,8 +268,8 @@ inline void to_json(BasicJsonType& j, T b) noexcept
 }
 
 template<typename BasicJsonType,
-         enable_if_t<std::is_convertible<const std::vector<bool>::reference&, typename BasicJsonType::boolean_t>::value, int> = 0>
-inline void to_json(BasicJsonType& j, const std::vector<bool>::reference& b) noexcept
+         enable_if_t<std::is_convertible<std::vector<bool>::const_reference&, typename BasicJsonType::boolean_t>::value, int> = 0>
+inline void to_json(BasicJsonType& j, std::vector<bool>::const_reference& b) noexcept
 {
     external_constructor<value_t::boolean>::construct(j, static_cast<typename BasicJsonType::boolean_t>(b));
 }