Is there any reason why in can't work with dynamic arrays?

[JN]

On Tuesday, 17 September 2019 at 17:43:39 UTC, Brett wrote:
> T[] x;
>
> if (y in x) ...
>
> It just checks to see if y is in between 0 and length. Clearly 
> y has to be an int and clearly the semantics are equivalent to 
> AA and so it all works out rather than having an arbitrary 
> special case.
>
> This is helpful when one has generate algorithms that can work 
> with AA's or DA's that use in.

Wow! Does really in work like that with arrays? This is terrible. 
I'd never expect in to check if index is in range. In every 
language in existence (that I know of) that has 'in', 'in' is a 
search for existence of value, whether a linear search is 
required or not.