[Bug c++/76262] New: list-initialization prefers initializer_list over copy constructor

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=76262

            Bug ID: 76262
           Summary: list-initialization prefers initializer_list over copy
                    constructor
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

In this example:

#include <iostream>

struct X {
    X(std::initializer_list<int >) { std::cout << '1'; }
    X(X const& ) { std::cout << '2'; }
    operator int() { return 0; }
};

int main() {
    X x{1};
    X y{x};
}

gcc 5.3, 6.1, and 7.0 all print 11. But the wording in [over.ics.rank] favoring
initializer_list<X> only applies if the conversion sequences are of the same
form, and in this case they're not - the initializer_list<X> constructor
requires a user-defined conversion.