Conditional Pure?

[so]

> nothrow too and other future attributes too.
>
> Funny, that was going to be my next comment. :)
> The only thing that scares me a bit is that code like this:
>
> public(isPublic!(TFn)) static(isStatic!(TFn)) int memoize(TFn)(TFn fn)
>     pure(isPure!(TFn))
>     if (isCallable!(TFn))
> {
>     //etc.
> }

A question,
Is this the only use case? I mean do we always want something like  
"xxx(isxxx(T))"?
If so, this mess is quite pointless.