[Bug c++/87605] New: Ternary uses explicit copy constructor for lvalue-to-rvalue conversion

[namark at disroot dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87605

            Bug ID: 87605
           Summary: Ternary uses explicit copy constructor for
                    lvalue-to-rvalue conversion
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: namark at disroot dot org
  Target Milestone: ---

The code below compiles and outputs "copy" to stdout when ran.

#include <cstdio>
struct A
{
    A(){}
    explicit A(const A&) {std::puts("copy");}
};

int main() 
{
    A a;
    const A& b = true ? a : A();
    return 0;
}

I'm using compiler version 8.1.0, but testing on godbolt.org all version
available there, except 4.1.2, do the same. 4.1.2 will do it as well if the
"const A& b = " is removed, leaving just the ternary by itself.

This felt wrong to me, but I'm not very well versed in the standard, so asked
on stack overflow 
https://stackoverflow.com/questions/52720175/ternary-allowed-to-call-an-explicit-copy-constructor-implicitly 
and the provided answer, confirming that this is a bug, seems correct.