Missing Symbol Accessing Templated Function Through Interface

[crimaniak via Digitalmars-d-learn]

On Tuesday, 8 March 2016 at 11:50:32 UTC, Peter wrote:
> Hi,
>
> Can anyone explain to me what's causing the following code to 
> generate a missing symbol error...

Relevant comment: https://issues.dlang.org/show_bug.cgi?id=8553#c1