Fix 'const' qualifier on bool& has no effect (#3678)

* Fix 'const' qualifier on bool& has no effect Thanks, @georgthegreat, for pointing out this issue. * Extend std::vector<bool> unit test
sandialabs · Aug 7, 2022 · f1e3407 · f1e3407
1 parent bfbe774
commit f1e3407
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Showing 3 changed files with 28 additions and 7 deletions.
diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
@@ -267,9 +267,15 @@ inline void to_json(BasicJsonType& j, T b) noexcept
     external_constructor<value_t::boolean>::construct(j, b);
 }
 
-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
+template < typename BasicJsonType, typename BoolRef,
+           enable_if_t <
+               ((std::is_same<std::vector<bool>::reference, BoolRef>::value
+                 && !std::is_same <std::vector<bool>::reference, typename BasicJsonType::boolean_t&>::value)
+                || (std::is_same<std::vector<bool>::const_reference, BoolRef>::value
+                    && !std::is_same <detail::uncvref_t<std::vector<bool>::const_reference>,
+                                      typename BasicJsonType::boolean_t >::value))
+               && std::is_convertible<const BoolRef&, typename BasicJsonType::boolean_t>::value, int > = 0 >
+inline void to_json(BasicJsonType& j, const BoolRef& b) noexcept
 {
     external_constructor<value_t::boolean>::construct(j, static_cast<typename BasicJsonType::boolean_t>(b));
 }

diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
@@ -5500,9 +5500,15 @@ inline void to_json(BasicJsonType& j, T b) noexcept
     external_constructor<value_t::boolean>::construct(j, b);
 }
 
-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
+template < typename BasicJsonType, typename BoolRef,
+           enable_if_t <
+               ((std::is_same<std::vector<bool>::reference, BoolRef>::value
+                 && !std::is_same <std::vector<bool>::reference, typename BasicJsonType::boolean_t&>::value)
+                || (std::is_same<std::vector<bool>::const_reference, BoolRef>::value
+                    && !std::is_same <detail::uncvref_t<std::vector<bool>::const_reference>,
+                                      typename BasicJsonType::boolean_t >::value))
+               && std::is_convertible<const BoolRef&, typename BasicJsonType::boolean_t>::value, int > = 0 >
+inline void to_json(BasicJsonType& j, const BoolRef& b) noexcept
 {
     external_constructor<value_t::boolean>::construct(j, static_cast<typename BasicJsonType::boolean_t>(b));
 }

diff --git a/tests/src/unit-constructor1.cpp b/tests/src/unit-constructor1.cpp
@@ -454,10 +454,19 @@ TEST_CASE("constructors")
             CHECK(j.type() == json::value_t::boolean);
         }
 
-        SECTION("from std::vector<bool>::refrence")
+        SECTION("from std::vector<bool>::reference")
         {
             std::vector<bool> v{true};
             json j(v[0]);
+            CHECK(std::is_same<decltype(v[0]), std::vector<bool>::reference>::value);
+            CHECK(j.type() == json::value_t::boolean);
+        }
+
+        SECTION("from std::vector<bool>::const_reference")
+        {
+            const std::vector<bool> v{true};
+            json j(v[0]);
+            CHECK(std::is_same<decltype(v[0]), std::vector<bool>::const_reference>::value);
             CHECK(j.type() == json::value_t::boolean);
         }
     }