drus:
I'm trying to disable ctor that has non-std::string constructible type. My 1st attempt was like this :
#include
struct A
{
template::value>::type>
A(U&& val)
{
std::cout (val)) }
template::value>::type>
A(U&& val)
{
std::cout }
};
int main()
{
A a1(1);
A a2("hello");
A a3(std::string("hello"));
}
But compilation fails in line
A a1(1);
with the following error message :
error C2535: 'A::A(U &&)': member function already defined or declared (live example).
That means, that both conditions for SFINAE succeeded and both ctors are used.
I moved on and tried the following approach :
#include
struct A
{
template
A(U&& val, typename std::enable_if<:is_constructible u>::value>::type* = nullptr)
{
std::cout (val)) }
template
A(U&& val, typename std::enable_if::value>::type* = nullptr)
{
std::cout }
};
int main()
{
A a1(1);
A a2("hello");
A a3(std::string("hello"));
}
Luckily it compiles and works fine (live example).
So far, Im pretty fine with the 2nd solution but I don't really understand why the 1st approach with enabling/disabling ctor using templated parameter doesn't work.
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