What could this be?

[Simen Kjærås]

On Monday, 11 May 2020 at 11:20:51 UTC, Joel wrote:
> I'm gotten stuck with this error - "..is not visible from 
> module.."

Without some code it's hard to say exactly, but this generally 
means you're referencing a private symbol in a different module:

module foo;
private struct S {}

module bar;
import foo;
foo.S s; // foo.S is not visible from module bar

--
   Simen