nested templates using Complex! with slices, ... confused, I am!

[james.p.leblanc]

Suppose "foo_double" should return a complex double slice, with 
double input args.
Similarly "foo_float" should return a float slice, with float 
input args.

I thought it should be easy to parameterize with a template 
taking a SINGLE
argument, either a"double" or "float" as follows:

>import std.stdio;
>import std.complex;
>
>Complex!double[] foo_double(double x, double y){
>   auto r = [x, x];
>   auto i = [y, y];
>   auto z = [ Complex!double(x, y), Complex!double(x,y) ];
>   return z;
>}
>
>Complex!float[] foo_float(float x, float y){
>   auto r = [x, x];
>   auto i = [y, y];
>   auto z = [ Complex!float(x, y), Complex!float(x,y) ];
>   return z;
>}
>
>**T[] foo_temp(Complex!T[])(T x, T y){
>   auto r = [x, x];
>   auto i = [y, y];
>   auto z = [ Complex!T(x, y), Complex!T(x,y) ];
>   return z;
>}**
>
>void main(){
>   auto yd = foo_double(1.1, 2.2);
>   writeln(yd); ...
> }

But, no ... I am WRONG!  I get the message:

qqq.d(18): Error: identifier expected for template value parameter

Nested templates using Complex! really have me confused.  How 
should I
be thinking about such things in order to understand better?

Best Regards,
James