How to use template Object in interface?

[zoujiaqing]

On Tuesday, 25 June 2019 at 12:11:47 UTC, zoujiaqing wrote:
> hunt-cache current version use template implemention adapter 
> changes.
>
> I want use Interface to define Adapter, this master code unable 
> to comple.
>
> How to do it? D programming language design flaws?
>
> ```bash
> git clone https://github.com/huntlabs/hunt-cache
> cd hunt-cache/example
> dub run -v
>
> ...
>
> source/app.d(29,19): Error: no property name for type 
> Nullable!(User)
>
> ```

Error in this commit:
https://github.com/huntlabs/hunt-cache/commit/1f4ca85b47a7e62b41907152f8c8904e69a09975