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

[MysticZach via Digitalmars-d]

On Friday, 23 June 2017 at 00:17:23 UTC, Steven Schveighoffer 
wrote:
> int foo()
> out(result)
> {
> }
>
> what does this mean? Does it mean assert(result) on the out 
> contract, or this is the old form of out?
>
> If we didn't have contract syntax already, and many existing 
> code bases that use it, I'd say this would be the way to go.

The current grammar is:

OutStatement:
    out ( Identifier ) { Statement }
    out { Statement }

So one way out is simply to demand that there be more than just 
an identifier when checking in the new way. So you'd have to 
require more tokens, e.g.`out(result !is null)` instead of just 
`out(result)` in order for the parser to easily distinguish 
between the two. It's a little messy. On the other hand, 
requiring two sets of parens is clean, but ugly. So it's a choice 
between ugly and messy, unless someone comes up with something 
more elegant.