Brace constructing a toml::value inserts a new array element in GCC 10.2.1

[andrewkcorcoran]

toml11v3.7.0

The toml2 variable in the below example is copy constructed incorrectly and has an empty array inserted on GCC but is correctly constructed on clang. The error looks to be to do with the toml::value std::intializer_list constructor std::enable_if being too broad (toml/value.hpp:840).

  #include <iostream>
  #include <sstream>

  #include "toml.hpp"

  int main()
  {
      auto stream = std::istringstream{"a = 1"};
      auto toml1 = toml::parse(stream);
      auto toml2 = toml::value{toml1};
      auto toml3 = toml::value(toml1);
      std::cout << toml1 << toml2 << toml3;
      return EXIT_SUCCESS;
  }

$ g++ --version
g++ (GCC) 10.2.1 20200804 (Red Hat 10.2.1-2)
./mva_gcc
a = 1
[[]]
a = 1
a = 1

$ clang++ --version
clang version 10.0.1 (Red Hat 10.0.1-4.el7)
./mva_clang
a = 1
a = 1
a = 1

[jackwil1]

I am also having this issue

[vadz]

This is really not a nice problem to run into when initializing a class member with the result of parse(), e.g.

struct config_file {
  explicit config_file(const char* filename) : root_{toml::parse(filename)} {}

  const toml::value root_;
};

results in root_ being an array, completely unexpectedly.