attachment set

ulidtko@… — Thu, 17 May 2012 17:39:54 GMT

attachment → substitution_failure_test.cpp

reproducing example

component changed; owner set

viboes — Mon, 28 May 2012 17:15:41 GMT

owner set to Joel de Guzman
component None → fusion

anonymous — Thu, 21 Jun 2012 09:27:17 GMT

First reported here: http://stackoverflow.com/questions/10632848/boost-fusion-invoke-and-sfinae

If fixed, closure in the form of a note on the original Stack Overflow question would be very much appreciated.

status changed; resolution set

Joel de Guzman — Tue, 04 Sep 2012 15:04:17 GMT

status new → closed
resolution → fixed

I fixed this in trunk. The first test:

try_invoke<F, boost::fusion::vector<float>> (0);

now compiles just fine. The second test however is (IMO) erroneous:

try_invoke<F, boost::fusion::vector<junk>> (0);

This cannot select the fallback overload because

typename boost::fusion::result_of::invoke<F, Sequence>::type

will be erroneous and will not trigger SFINAE. The code attached is equivalent to this:

#include <boost/utility/result_of.hpp> #include <iostream>

int foo(int); struct junk {};

template <typename F, typename Arg> typename boost::result_of<F(Arg)>::type call(int) {

return F(Arg());

}

template <typename F, typename Arg> void call(long) {

fallback std::cout << "fallback" << std::endl;

}

int main() {

call<int(*)(int), junk>(123);

}

which will give you an error. Notice though that if I replace:

typename boost::result_of<F(Arg)>::type

with

decltype(F(Arg()))

then it works. So the question now falls into the hands of the Boost::result_of maintainers. If you think this should work, then, go add a ticket to boost::result_of.

I'm closing this one.

Boost C++ Libraries: Ticket #6915: boost::fusion::result_of::invoke compilation errors

attachment set

component changed; owner set

status changed; resolution set