Template-Parameterized Variadic isInstaceOf

["Nordlöw" via Digitalmars-d-learn]

To implement a new trait

     isSortedRange(R, pred)

needed for SortedRange specializations I need a variant of

     enum bool isInstanceOf(alias S, T) = is(T == S!Args, Args...);

that takes the `pred` argument aswell.

But I have no clue what to do with

     enum bool isInstanceOf(alias S, T, TParams) = is(T == S!Args, 
Args...);

because I dont' understand the syntax

     is(T == S!Args, Args...);

Can somebody please explain and help out with variadic version of 
`isInstanceOf`?