Using IFTI to only allow params of a certain template instance?

Jarrett Billingsley kb3ctd2 at
Fri Jul 6 15:32:15 PDT 2007

Say I have a function which has a parameter whose type has to be an instance 
of a particular template, like so:

class Temp(T)
    // blah

OK, so the first thing I tried was something like this:

void func(T, U : Temp!(T))(U param)


but when I call it like

auto t = new Temp!(int)();

the compiler doesn't accept it, it says it can't deduce the types.  It looks 
right to me, though.

If I switch the order of the template parameters to func, I get different 
errors (notably, an error saying that I can't have a specialization for a 
deduced parameter).

Is there any way to restrict the parameter like this?  I thought about using 
a static assert with is(), but I can't think of how I'd check that the type 
of the parameter is an instance of Temp. 

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