Improve "Improve Contract Syntax" DIP 1009

[Patrick Schluter]

On Thursday, 2 November 2017 at 08:58:03 UTC, codephantom wrote:

> but now we want free floating statements in D?
>
> like:
> ----------------------
> in(a > 0)
> in(b >= 0, "b cannot be negative!")
> out(r; r > 0, "return must be positive")
> out(; a != 0)
> --------------------
>
> Now, I'm new to D (I only discovered it a month or so 
> ago)...but do free floating statements already exist in the 
> language?
>
if() in template constraints are similar, so it is nothing 
shockingly out of character.
They are not free floating either as they are part of the 
function definition

int foo(int a) in(a >= 0)
do {
...whatever
}

vs

int foo(int a)
in {
    assert(a >= 0);
}
do {
...whatever
}