DIP33: A standard exception hierarchy

[Dicebot]

On Wednesday, 3 April 2013 at 18:37:09 UTC, Jonathan M Davis 
wrote:
> ... you could do something like
>
> Verify!T verifyFoo(T param)
> {
>  //do checks...
>  return Verify!T(param);
> }
>
> void foo(T param)
> {
>  foo(verifyFoo(param));
> }
>
> void foo(Verified!T param)
> {
>  ...
>
> }
>
> That would be rather intrusive, but you _could_ do it if you 
> wanted to.

What problems do you see with this (or similar) approach? I find 
it very straightforward and no overhead is really necessary. 
Isn't it exactly what type system is for - enforcing static 
guarantees in between different parts of application?