Problems with implicit template instantiation: Tail Currying

[downs]

Russell Lewis wrote:
> I'm trying to write a template to perform function currying of the 
> *last* argument to a delegate, and I can't get implicit instantiation to 
> work with my template.  Take a look at this example code:
> 
> =======
> void delegate(U) Curry    (A,U...)(void delegate(A,U) dg,A arg) {
>   return delegate void(U) {};
> }
> void delegate(U) CurryTail(A,U...)(void delegate(U,A) dg,A arg) {
>   return delegate void(U) {};
> }
> void foo() {
>   void delegate(uint,char[],uint) dg;
>   uint i;
>   Curry    (dg,i);
>   CurryTail(dg,i);
> }
> =======
> 
> The CurryTail call fails with the following errors:
> 
> foo.d(11): template foo.CurryTail(A,U...) does not match any template 
> declaration
> foo.d(11): template foo.CurryTail(A,U...) cannot deduce template 
> function from argument types (void delegate(uint, char[], uint),uint)
> 
> 
> 
> So: if the Curry() call works, why doesn't the CurryTail() call?  Is 
> this a bug, or some sort of design restriction?
> 
> Russ
Try like so:
void delegate(T[0..$-1]) CurryTail(P, T...) (void delegate(T) dg, P arg) {
	static assert(is(P: T[$-1]),
		"Invalid type: "~P.toString~" cannot be converted to "~T[$-1].toString);
	return delegate void(T[0..$-1] t) {};
}