what exactly is string length?

[Виталий Фадеев]

On Friday, 2 April 2021 at 04:32:53 UTC, mw wrote:
> https://run.dlang.io/is/B4jcno
>
> ---
> import std;
> import std.conv : text;
>
>
> void main()
> {
>     char[6] s;
>     s = "abc";
>     writeln(s, s.length);  // abc6, ok it's the static array's 
> length
>
>     string t = text("head-", s, "-tail");
>     writeln(t, t.length);  // head-abc-tail16, why?
> }
> ---
>
> Why the last output is 16 instead of 13, t's type is string 
> here.

Test this:
https://run.dlang.io/is/Cq4vjP