Why do I have to cast arguments from int to byte?

[kdevel]

On Friday, 13 October 2017 at 07:47:55 UTC, Daniel Kozak wrote:
> but it works ok with immutable, so until you really need to 
> change bar you can use
>
> immutable bar = 9;
> foo!byte(bar + 1);

As Adam wrote two days ago: 'D doesn't do implicit narrowing 
conversion... so x + 1 becomes int, but then int to byte requires 
an explicit cast (unless the compiler can prove the range in that 
particular expression - this is called "value range 
propagation").'