DIP 1009--Improve Contract Usability--Preliminary Review Round 1

[MysticZach via Digitalmars-d]

On Thursday, 22 June 2017 at 12:21:29 UTC, MysticZach wrote:
> I start to get the nagging feeling that your point about the 
> limitation in D's DbC implementation is actually the fatal flaw 
> here. It's currently _illegal_ (outside of interface 
> declarations) to expose the signature separately from the body, 
> which, as you point out,  is more or less the whole point of 
> DbC. <shrug> The existing system is itself distinctly _worse_ 
> than just writing out asserts manually... and as far as I can 
> tell,  none of the alternative syntaxes is a decisive 
> improvement over it. Yours looks the best, but implying 
> `assert` in the grammar seems to be going too far, especially 
> for a DbC system that is only half functional. If the `assert` 
> system were made more user-definable, it would make more sense. 
> Do you agree with me on this?
>
> Plans to improve `assert` are already in the air. Maybe we 
> should wait on them before promoting your suggestion?

Conversely, as Moritz suggests, contracts could have their own 
separate logic, with optional user-defined hooks. Do you have a 
suggestion on how to implement this behind the scenes?