Compile error: template argument deduction/substitution failed

[ripwu]

• What is the issue you have?

failed to compile

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?

code:

#include "json.hpp"

struct RealmList {
    int32_t person_abilitiy;
    std::vector<std::vector<int32_t>> consumeitem;
    std::vector<std::vector<int32_t>> attr;
};

struct QtRealm {
    int32_t open_level;
    std::vector<RealmList> realm_list;
};

namespace nlohmann {
namespace detail {
    void from_json(const json & j, RealmList & x);
    void from_json(const json & j, QtRealm & x);

    inline void from_json(const json & j, RealmList& x) {
        x.person_abilitiy = j.at("person_abilitiy").get<int32_t>();
        x.consumeitem = j.at("consumeitem").get<std::vector<std::vector<int32_t>>>();
        x.attr = j.at("attr").get<std::vector<std::vector<int32_t>>>();
    }

    inline void from_json(const json & j, QtRealm& x) {
        x.open_level = j.at("open_level").get<int32_t>();
        x.realm_list = j.at("realm_list").get<std::vector<RealmList>>();
    }
}
}

int main(int argc, char *argv[])
{
    return 0;
}

result:

root@localhost:/# /usr/bin/g++ main.cpp -O0 -g3 -Wall -Wno-literal-suffix -Wnarrowing -Wno-write-strings -fpermissive -std=c++11
main.cpp: In function ‘void nlohmann::detail::from_json(const json&, QtRealm&)’:
main.cpp:27:71: error: no matching function for call to ‘nlohmann::basic_json<>::get() const’
         x.realm_list = j.at("realm_list").get<std::vector<RealmList>>();
                                                                       ^
main.cpp:27:71: note: candidates are:
In file included from main.cpp:1:0:
json.hpp:14883:16: note: template<class BasicJsonType, typename std::enable_if<std::is_same<typename std::remove_const<_Tp>::type, nlohmann::basic_json<> >::value, int>::type <anonymous> > nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer> nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with BasicJsonType = BasicJsonType; typename std::enable_if<std::is_same<typename std::remove_const<BasicJsonType>::type, nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer> >::value, int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     basic_json get() const
                ^
json.hpp:14883:16: note:   template argument deduction/substitution failed:
json.hpp:14882:25: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                  int> = 0>
                         ^
json.hpp:14882:25: note: invalid template non-type parameter
json.hpp:14906:19: note: template<class BasicJsonType, typename std::enable_if<((! std::is_same<BasicJsonType, nlohmann::basic_json<> >::value) && nlohmann::detail::is_basic_json<BasicJsonType>::value), int>::type <anonymous> > BasicJsonType nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with BasicJsonType = BasicJsonType; typename std::enable_if<((! std::is_same<BasicJsonType, nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer> >::value) && nlohmann::detail::is_basic_json<BasicJsonType>::value), int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     BasicJsonType get() const
                   ^
json.hpp:14906:19: note:   template argument deduction/substitution failed:
json.hpp:14905:70: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                  detail::is_basic_json<BasicJsonType>::value, int> = 0>
                                                                      ^
json.hpp:14905:70: note: invalid template non-type parameter
json.hpp:14956:15: note: template<class ValueTypeCV, class ValueType, typename std::enable_if<(((! nlohmann::detail::is_basic_json<T>::value) && nlohmann::detail::has_from_json<nlohmann::basic_json<>, ValueType, void>::value) && (! nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<>, ValueType, void>::value)), int>::type <anonymous> > ValueType nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with ValueTypeCV = ValueTypeCV; ValueType = ValueType; typename std::enable_if<(((! nlohmann::detail::is_basic_json<U>::value) && nlohmann::detail::has_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value) && (! nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value)), int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     ValueType get() const noexcept(noexcept(
               ^
json.hpp:14956:15: note:   template argument deduction/substitution failed:
json.hpp:14955:25: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                  int> = 0>
                         ^
json.hpp:14955:25: note: invalid template non-type parameter
json.hpp:15007:15: note: template<class ValueTypeCV, class ValueType, typename std::enable_if<((! std::is_same<nlohmann::basic_json<>, ValueType>::value) && nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<>, ValueType, void>::value), int>::type <anonymous> > ValueType nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with ValueTypeCV = ValueTypeCV; ValueType = ValueType; typename std::enable_if<((! std::is_same<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value) && nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value), int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     ValueType get() const noexcept(noexcept(
               ^
json.hpp:15007:15: note:   template argument deduction/substitution failed:
json.hpp:15006:41: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                                  int> = 0>
                                         ^
json.hpp:15006:41: note: invalid template non-type parameter
json.hpp:15137:10: note: template<class PointerType, typename std::enable_if<std::is_pointer<_Tp>::value, int>::type <anonymous> > decltype (declval<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::basic_json_t&>().get_ptr<PointerType>()) nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() [with PointerType = PointerType; typename std::enable_if<std::is_pointer<_Ptr>::value, int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     auto get() noexcept -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
          ^
json.hpp:15137:10: note:   template argument deduction/substitution failed:
json.hpp:15136:68: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                  std::is_pointer<PointerType>::value, int>::type = 0>
                                                                    ^
json.hpp:15136:68: note: invalid template non-type parameter
json.hpp:15149:20: note: template<class PointerType, typename std::enable_if<std::is_pointer<_Tp>::value, int>::type <anonymous> > constexpr decltype (declval<const basic_json_t&>().get_ptr<PointerType>()) nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with PointerType = PointerType; typename std::enable_if<std::is_pointer<_Ptr>::value, int>::type <anonymous> = <enumerator>; ObjectType = std::map; ArrayType = std::vector; StringType = std::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]
     constexpr auto get() const noexcept -> decltype(std::declval<const basic_json_t&>().template get_ptr<PointerType>())
                    ^
json.hpp:15149:20: note:   template argument deduction/substitution failed:
json.hpp:15148:68: error: no type named ‘type’ in ‘struct std::enable_if<false, int>’
                  std::is_pointer<PointerType>::value, int>::type = 0>
                                                                    ^
json.hpp:15148:68: note: invalid template non-type parameter

• What is the expected behavior?

• And what is the actual behavior instead?

template argument deduction/substitution failed

• Which compiler and operating system are you using? Is it a supported compiler?

• Did you use a released version of the library or the version from the develop branch?

gcc version 4.8.5 20150623 (Red Hat 4.8.5-36) (GCC)

uname -a
Linux localhost.localdomain 3.10.0-957.el7.x86_64 #1 SMP Thu Nov 8 23:39:32 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

From the brance

• If you experience a compilation error: can you compile and run the unit tests?

I have run the unit tests, 100% tests passed, 0 tests failed out of 88.

[ripwu]

Sorry, I miss the document saying that the methods MUST be in my type's namespace.
Closed.

[GrubbyHalo]

@ripwu Thanks for that!