std.typecons.Proxy + inheritance breaks cast'ing to inherited type

[Lukasz Wrzosek via Digitalmars-d-learn]

On Monday, 16 March 2015 at 12:03:12 UTC, John Colvin wrote:
>
> What behaviour would you expect if both IA and C inherited from 
> IB?

This case should assert at compile time.
But my example shows that case with implicit case is working, but 
the explicit cast is not. That seems to be incorrect IMO.