Re: [boost] [PFR][review] Andrzej's review

6 Oct 2020


      вт, 6 окт. 2020 г. в 14:42, Andrzej Krzemienski via Boost
:
...
wt., 6 paź 2020 o 13:29 Peter Dimov via Boost 
napisał(a):
...
Andrzej Krzemienski wrote:
...
3. The library buds on a basic concept of "Base-less aggregate".
That's not really true though, is it? E.g.
#include 
#include <string>
#include <iostream>
struct X
{
    std::string a;
};
struct Y
{
    std::string b;
};
struct Z: X, Y
{
    std::string c;
};
int main()
{
    std::cout << boost::pfr::tuple_size_v<Z> << std::endl;
}
compiles and prints "3". Bases are treated as members by the precise API.
But this is only for tuple_size. If you do a for_each, the compilation
breaks:
```
Z z {{}, {}, {}};
boost::pfr::for_each_field(z, [](auto const&){});
```
This is because brace initialization of aggregates is "incompatible" with
structured binding for aggregates now in C++20.
I think we took the wrong turn in C++17, when allowed inheritance for
aggregates. Unfortunately that's not getting better with time :(

-- 
Best regards,
Antony Polukhin