在clang中使用别名模板时，有没有办法缩短模板化的类名？

Question

这是前一个问题here的后续行动。基本上，下面的程序

#include <memory> 

// Create a class parameterized on a template 
template <template <typename> class XX> 
struct Foo{}; 

// Some template with a long name 
template <typename T> 
struct ReallyLongFileNameThatIHateToType { 
}; 

// Alias to shorten name 
template <typename T> 
using Bar = ReallyLongFileNameThatIHateToType <T>; 

int main() { 
    std::unique_ptr<Foo<ReallyLongFileNameThatIHateToType>> foo = 
     std::make_unique<Foo<Bar>>(); 
} 

作品只是用gcc罚款;铛

g++ -std=c++14 test04.cpp -o test04 
clang++ -std=c++14 test04.cpp -o test04 
test04.cpp:20:61: error: no viable conversion from 'unique_ptr<Foo<template 
     Bar>>' to 
     'unique_ptr<Foo<template ReallyLongFileNameThatIHateToType>>' 
    std::unique_ptr<Foo<ReallyLongFileNameThatIHateToType>> foo = 
                  ^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/bits/unique_ptr.h:200:17: note: 
     candidate constructor not viable: no known conversion from 'typename 
     _MakeUniq<Foo<Bar> >::__single_object' (aka 'unique_ptr<Foo<Bar> >') to 
     'nullptr_t' for 1st argument 
     constexpr unique_ptr(nullptr_t) noexcept : unique_ptr() { } 
       ^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/bits/unique_ptr.h:205:7: note: 
     candidate constructor not viable: no known conversion from 'typename 
     _MakeUniq<Foo<Bar> >::__single_object' (aka 'unique_ptr<Foo<Bar> >') to 
     'std::unique_ptr<Foo<ReallyLongFileNameThatIHateToType>, 
     std::default_delete<Foo<ReallyLongFileNameThatIHateToType> > > &&' for 1st 
     argument 
     unique_ptr(unique_ptr&& __u) noexcept 
    ^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/bits/unique_ptr.h:356:7: note: 
     candidate constructor not viable: no known conversion from 'typename 
     _MakeUniq<Foo<Bar> >::__single_object' (aka 'unique_ptr<Foo<Bar> >') to 
     'const std::unique_ptr<Foo<ReallyLongFileNameThatIHateToType>, 
     std::default_delete<Foo<ReallyLongFileNameThatIHateToType> > > &' for 1st 
     argument 
     unique_ptr(const unique_ptr&) = delete; 
    ^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/type_traits:1957:41: note: 
     candidate template ignored: disabled by 'enable_if' [with _Up = Foo<Bar>, 
     _Ep = std::default_delete<Foo<Bar> >] 
    using _Require = typename enable_if<__and_<_Cond...>::value>::type; 
             ^
/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/bits/unique_ptr.h:228:2: note: 
     candidate template ignored: could not match 'auto_ptr' against 
     'unique_ptr' 
     unique_ptr(auto_ptr<_Up>&& __u) noexcept; 
     ^
1 error generated. 
Makefile:2: recipe for target 'all' failed 
make: *** [all] Error 1 

由于联动消息中指出的那样，这是CWG问题1244不管怎么说，有另一种方式来缩短与clang一起使用的名字？通常，我在模板类上有参数化代码，但我不想一遍又一遍地输出完整的参数名称。在使用gcc时，我只需创建别名模板并在一天内调用它。显然，在叮当声中，这是行不通的，那么是否有不同的机制来实现同样的效果？

Answer 1

作为一种解决方法，您可以通过将模板模板参数传递给某个辅助结构以使用模板模板参数将其设置为一种解决方法。 （在clang ++，C++ 14中工作）：

#include <memory> 

// Create a class parameterized on a template 
template <template <typename> class XX> 
struct Foo{}; 

// Some template with a long name 
template <typename T> 
struct ReallyLongFileNameThatIHateToType { 
}; 

template <template <template <class> class> class FF> 
struct Bar { 
    using type = FF<ReallyLongFileNameThatIHateToType>; 
}; 

template <template <template <class> class> class FF> 
using Bar_t = typename Bar<FF>::type; 


int main() { 
    std::unique_ptr<Foo<ReallyLongFileNameThatIHateToType>> foo = 
     std::make_unique<Bar_t<Foo>>(); 
}