Making preconditions better specified and faster

[Caspar Kielwein via Digitalmars-d]

On Thursday, 15 December 2016 at 18:48:22 UTC, Andrei 
Alexandrescu wrote:
> https://issues.dlang.org/show_bug.cgi?id=16975

I like it. It's a step in the right direction of making contracts 
more powerful.

I'd love if preconditions where available at the caller. This 
would make it possible to use preconditions for input scrubbing, 
even in release builds with disabled asserts.