Optional tags and attributes

[Stanislav Blinov]

On Saturday, 18 January 2014 at 00:23:14 UTC, Adam D. Ruppe wrote:
> Templates automatically infer their attributes based on the 
> input, so you don't have to specify them there.
>
> If you do a foo!(nothrow_function)(), foo is also nothrow 
> (unless, of course, it throws!)

This doesn't apply here. I'm not using function as a template 
paramter.

That's the whole case here. Suppose I'm writing a template class 
that's parametrized by some type, and in my method I want to call 
methods of that type. I cannot make any of my functions nothrow 
until I am sure the methods I call will not throw, and the 
compiler will tell me. And how can I be sure they don't throw if 
it's an arbitrary type? I can check it, sure, with that 
isNoThrow() template. But how then to use that information in my 
own function declaration?