From 5a6cc0c9b5732bf7deb2d7e7a8659ee4f58fd06f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= <theo.delrieu@tanker.io>
Date: Mon, 12 Feb 2018 10:47:17 +0100
Subject: [PATCH] Fix constraints on from_json(CompatibleArrayType)

Fixes #924
---
 .../nlohmann/detail/conversions/from_json.hpp |  2 +-
 single_include/nlohmann/json.hpp              |  2 +-
 test/src/unit-inspection.cpp                  |  4 ++--
 test/src/unit-udt.cpp                         | 22 +++++++++++++++++++
 4 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
index 8ea0284a15..70e1e1e012 100644
--- a/include/nlohmann/detail/conversions/from_json.hpp
+++ b/include/nlohmann/detail/conversions/from_json.hpp
@@ -179,7 +179,7 @@ void from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr, priorit
 
 template<typename BasicJsonType, typename CompatibleArrayType,
          enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
-                     std::is_convertible<BasicJsonType, typename CompatibleArrayType::value_type>::value and
+                     has_from_json<BasicJsonType, typename CompatibleArrayType::value_type>::value and
                      not std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value, int> = 0>
 void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
 {
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index a7c009c0d2..d4b147765e 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -1086,7 +1086,7 @@ void from_json_array_impl(const BasicJsonType& j, std::array<T, N>& arr, priorit
 
 template<typename BasicJsonType, typename CompatibleArrayType,
          enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
-                     std::is_convertible<BasicJsonType, typename CompatibleArrayType::value_type>::value and
+                     has_from_json<BasicJsonType, typename CompatibleArrayType::value_type>::value and
                      not std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value, int> = 0>
 void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
 {
diff --git a/test/src/unit-inspection.cpp b/test/src/unit-inspection.cpp
index 5facb11674..4bee80d13b 100644
--- a/test/src/unit-inspection.cpp
+++ b/test/src/unit-inspection.cpp
@@ -316,8 +316,8 @@ TEST_CASE("object inspection")
     SECTION("round trips")
     {
         for (const auto& s :
-                {"3.141592653589793", "1000000000000000010E5"
-                })
+    {"3.141592653589793", "1000000000000000010E5"
+    })
         {
             json j1 = json::parse(s);
             std::string s1 = j1.dump();
diff --git a/test/src/unit-udt.cpp b/test/src/unit-udt.cpp
index 17baf4e524..65ca788a69 100644
--- a/test/src/unit-udt.cpp
+++ b/test/src/unit-udt.cpp
@@ -711,3 +711,25 @@ TEST_CASE("an incomplete type does not trigger a compiler error in non-evaluated
 {
     static_assert(not is_constructible_patched<json, incomplete>::value, "");
 }
+
+namespace
+{
+class Evil
+{
+  public:
+    Evil() = default;
+    template <typename T>
+    Evil(T) {}
+};
+
+void from_json(const json&, Evil&) {}
+}
+
+TEST_CASE("Issue #924")
+{
+    // Prevent get<std::vector<Evil>>() to throw
+    auto j = json::array();
+
+    (void) j.get<Evil>();
+    (void) j.get<std::vector<Evil>>();
+}