This code

import std.stdio;
import std.typecons;

template mytemp(T...)
{
    static if(T.length == 1)
        enum mytemp = tuple(T[0]);
    else
        enum mytemp = tuple(T[0], mytemp!(T[1..$]).expand);
}

void main()
{
    writeln(mytemp!(5));
    writeln(mytemp!(5, 10, 7));
    writeln(mytemp!(true));
    writeln(mytemp!(true, false, true));
    writeln(mytemp!("hello"));
    writeln(mytemp!("hello", "world"));
}


results in this output

Tuple!(int)(0)
Tuple!(int,int,int)(0, 0, 0)
Tuple!(bool)(false)
Tuple!(bool,bool,bool)(false, false, false)
Tuple!(string)()
Tuple!(string,string)(, )


If I change it to

import std.stdio;
import std.typecons;

template mytemp(T...)
{
    enum mytemp = T[0];
}

void main()
{
    writeln(mytemp!(5));
    writeln(mytemp!(true));
    writeln(mytemp!("hello"));
}


I get

5
true
hello


So obviously, there's something wrong with tuple here. And it's pretty crippling for my current project actually.