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

[MysticZach via Digitalmars-d]

On Friday, 23 June 2017 at 16:21:28 UTC, H. S. Teoh wrote:
> On Fri, Jun 23, 2017 at 09:06:59AM +0000, Solomon E via 
> Digitalmars-d wrote: [...]
>> T foo(T)(T x, T y)
>>     in (x > 0, y > 0)
>>     out (r; r > 0)
>> {
>>     return x % y + 1;
>> }
>
> Hmm, I like this syntax for out-contracts!  It borrows from 
> existing foreach syntax, so it has some precedence, whereas the 
> previous proposal of `out(...)(...)` looks uglier and also 
> looks deceptively like a template function declaration.
>
> `out (r; r > 0)` gets my vote.
>
>
> OTOH, I don't like the comma in the in-contract.  Let's just 
> keep it as either separate clauses:
>
> 	in (x > 0)
> 	in (y > 0)

Yeah, my take is that the grammar for `assert`s applies to the 
new syntax as well. If the grammar for asserts is this:

AssertExpression:
   assert ( AssertParameters )

... then the grammar for the new syntax is:

InExpression:
   in ( AssertParameters )

OutExpression:
   out ( ; AssertParameters )
   out ( Identifier ; AssertParameters )