Constructing this " nlohmann::json jsondata{{{"domain","test"}}}; " creates an json array

[danielmevi]

I prefer to construct with {} instead of =.
Then when trying to swap the = with a pair of {} to one of the examples from documentation

json j2 = {
  {"pi", 3.141},
  {"happy", true},
  {"name", "Niels"},
  {"nothing", nullptr},
  {"answer", {
    {"everything", 42}
  }},
  {"list", {1, 0, 2}},
  {"object", {
    {"currency", "USD"},
    {"value", 42.99}
  }}
};

into a {} constructor, which ended up in:

json j2 { 
{
  {"pi", 3.141},
  {"happy", true},
  {"name", "Niels"},
  {"nothing", nullptr},
  {"answer", {
    {"everything", 42}
  }},
  {"list", {1, 0, 2}},
  {"object", {
    {"currency", "USD"},
    {"value", 42.99}
  }}
}
};

The run ended up with exception when trying to insert a new key j2["name"] = "Niels";

terminate called after throwing an instance of 'nlohmann::detail::type_error'
  what():  [json.exception.type_error.305] cannot use operator[] with a string argument with array

After some time I made it work by removing one of the 3 pairs of {} from the constructor. I am deducing that having 3 pairs of {} creates an array, which does not have the operator[] for it.

am I missing something? otherwise it would be good that documentation does mention it or that such constructor becomes invalid like std vector rejects a std::vector<int> vec{{{1,2}}}; with a <brace-enclosed initializer list> compilation error

[nlohmann]

This seems to be related to #2311.