Enum type deduction inside templates is not working

[Uranuz via Digitalmars-d-learn]

> I think, D is a typesafe language, therefore you can't use 
> variables with no type declaration.
>
> One thing you can search for, are templates but even there you 
> have to define a type:
>
> import std.stdio;
>
> enum Category : string { first = "first"}
>
> template Pair(T)
> {
> 	T t;
> 	T cat;
> }
>
>
> void main()
> {
> 	alias Pair!(string) a;
> 	a.cat = Category.first;
> 	a.t = "first";
>
> 	writeln(a.cat, " . ", a.t);
> }

Ok. I know that D is typesafe language, but I'm not going to do 
some implicit type casts in there, because type of Category.first 
is Category itself but not string or something. In this example 
`a.cat = Category.first;` tries to make implicit cast (I don't 
remember is it allowed or not)