Let's get the semantic around closure fixed.

[Adam D. Ruppe]

On Wednesday, 19 May 2021 at 19:01:59 UTC, Walter Bright wrote:
> Having a hidden allocation per loop will be completely 
> unexpected for such a simple looking loop for a lot of people. 
> That includes pretty much all of *us*, too.

Citation needed.

It is fairly well known that closures and objects are pretty 
interchangeable, so the allocation should surprise nobody. This 
is a very common pattern in several languages. And even ones that 
don't do this have workarounds - a function returning a function 
that gets called to capture the arguments (this works in D as 
well btw) - since the allocation is kinda the point of a closure.

Whereas the current behavior surprises most everybody AND is 
pretty useless.