Can't use toHexString

[badlink via Digitalmars-d-learn]

On Sunday, 19 July 2015 at 12:00:23 UTC, Kagamin wrote:
> http://forum.dlang.org/post/ydaeytbyxdnwlbpwkoma@forum.dlang.org

Argh... must use the search function first...

If I understand correctly in my case toHexString is returning a 
static char[len].
But why it gets silently converted to an immutable(char)[] ?
And why crcHexString works fine ? It's an alias to the same 
function...