Why doesn't curry work with multiple arguments?

[Andrej Mitrovic]

Here's a basic implementation:

import std.stdio;
import std.traits;
import std.metastrings;

template count(T...)
{
    enum count = T.length;
}

template curry(alias fun, args...)
{
    static if (args.length > (ParameterTypeTuple!fun).length)
    {
        static assert(0, Format!("Tried to pass %s arguments, max is %s.",
                                 count!args, (ParameterTypeTuple!fun).length));
    }

    static if (is(typeof(fun) == delegate) || is(typeof(fun) == function))
    {
        ReturnType!fun curry()
        {
            return fun(args);
        }
    }
}

void foo(int x, int y)
{
    writeln(x, y);
}

alias curry!(foo, 1, 2) bar;

void main()
{
	bar();
}

It will complain if you try to pass it more arguments than a function
can take. I didn't implement curry's original else clause because I
have no idea what's going on there (some comments would be useful in
Phobos implementations, people!......)

There is some wacky error if I didn't use the count template
workaround. If I try to use args.length twice, like so:
    static if (args.length > (ParameterTypeTuple!fun).length)
    {
        static assert(0, Format!("Tried to pass %s arguments, max is %s.",
                                 args.length, (ParameterTypeTuple!fun).length));
    }

Then I get back: identifier 'length' of 'args.length' is not defined

But it only errors out in the static assert, and yet it can check
args.length in the static if. Really weird.