Easy way to accept X and immutable X in parameters without overloading?

[Jack]

let's say a I have this:

void f(X foo) { }

but I'd like to make f() accept immutable X too so instead of 
cast away everywhere in the code where immutable(X) is passed to 
f() or make a overload for this, are there any way to accept both 
in same function? those function are callback-like functions, I 
have lots of them so already and would need to double, if I do 
add an overload just for the immutable. I did come up with 
something using templates, not sure if it's ugly:

void f(T)(T x)
if(is(T == C) || is(T == immutable(C)) {
// ...
}