C++ C++;17:在gcc中使用别名模板错误?
片段:C++ C++;17:在gcc中使用别名模板错误?,c++,templates,c++17,language-lawyer,C++,Templates,C++17,Language Lawyer,片段: #include <functional> template <typename T> struct CallableTrait; template <typename R, typename... Args> struct CallableTrait<std::function<R(Args...)>> { using ReturnType = R; }; template <typename Calla
#include <functional>
template <typename T>
struct CallableTrait;
template <typename R, typename... Args>
struct CallableTrait<std::function<R(Args...)>>
{
using ReturnType = R;
};
template <typename Callable>
using CallableTraitT = CallableTrait<decltype(std::function{std::declval<Callable>()})>;
template <typename Callable>
auto test(Callable&&)
{
using CallableInfo = CallableTraitT<Callable>;
static_assert(!std::is_void_v<typename CallableInfo::ReturnType>);
}
int main()
{
test([]() { return 42; });
return 0;
}
谁对谁错
编辑:
错误在此处跟踪问题在此处跟踪
[](){return 42;}
≠ std::function
。你想要的基本上就是我在这里所做的:@NathanOliver:Thx,但问题是为什么三个编译器中有两个是好的,而gcc认为这是错误的。@Eljay:但是CallableTraitT
“调用”std::function
…事实上,添加std::function
会让gcc高兴。我不这么认为。乔纳森只是简化了这个例子,还没有正式确认。@cigien:我的错。我不知道bugzilla中的语义。将进行防御性编辑。不用担心。谢谢你提交错误报告。对我来说,它确实像一只虫子,值得一提的是:)
prog.cc: In instantiation of 'auto test(Callable&&) [with Callable = main()::<lambda()>]':
prog.cc:25:29: required from here
prog.cc:20:25: error: invalid use of incomplete type 'struct CallableTrait<main()::<lambda()> >'
20 | static_assert(!std::is_void_v<typename CallableInfo::ReturnType>);
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prog.cc:5:8: note: declaration of 'struct CallableTrait<main()::<lambda()> >'
5 | struct CallableTrait;
|