how is this array subtyping inside struct (bug?) possible?

[Simen Kjærås]

On Monday, 10 August 2020 at 21:20:11 UTC, mw wrote:
> `writeln` should be a *view* (i.e read-only) function, it 
> shouldn't *internally* call anything thing that change the data 
> passed in.

So how should writeln deal with input ranges? Should it simply 
not be possible to print them, as that would (by their very 
nature) change them?

--
   Simen