Why do std.traits use template foo(args...) instead of foo(alias arg) ?

[Dicebot via Digitalmars-d-learn]

On Thursday, 18 December 2014 at 15:48:02 UTC, Mathias LANG wrote:
> An exemple being fullyQualifiedName:
> https://github.com/D-Programming-Language/phobos/blob/master/std/traits.d#L415
>
> I don't get this pattern. Is it documented somewhere ?

Full pattern looks like this:

template foo(T...)
     if (T.length == 1)

This is a way to workaround D template argument limitation - you 
can't have any parameter that accepts both types and symbols 
(`alias T` and `T` at once) other than variadic parameter. Limit 
variadic length to 1 and you emulate such "accepts anything" 
parameter.