Re: Should std::byte copy-list-initialization fail?

[Jeffrey Walton <noloader at gmail dot com>]

On Thu, Jul 13, 2017 at 3:55 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 13 July 2017 at 18:58, Jeffrey Walton wrote:
>> I'm working on Fedora 26 with GCC 7.1.1. I'm testing some C++17 code
>> and learning where some of the pain points are.
>>
>> $ cat test.cxx
>> #include <cstddef>
>> int main(int argc, char* argv[])
>> {
>>   std::byte b1 {0x65};
>>   std::byte b2 = {0x66};
>>   return 0;
>> }
>>
>> test.cxx: In function ‘int main(int, char**)’:
>> test.cxx:5:23: error: cannot convert ‘int’ to ‘std::byte’ in initialization
>>    std::byte b2 = {0x66};
>>                        ^
>>
>> It seems like there should be enough information for the compiler to
>> determine the list argument type and avoid the error (for b2) like in
>> the first example (for b1).
>>
>> Is the copy-list-initialization failure expected?
>
> Yes. You can't initialize a scoped enumeration type with an implicit conversion.
>
> enum class E { };
> E e = { 0 };  // error
> E e{ 0 }; // ok in C++17, error in C++14

Thanks Jonathan.

The comments explain my confusion. It seemed like both should succeed,
or both should fail. It looks like special accommodations were made
for list-initialization under C++17.

Jeff