How do I use in contract with interface?

[Steven Schveighoffer]

On 11/15/17 11:19 AM, Steven Schveighoffer wrote:
> But what doesn't make a lot of sense is the inability to declare the 
> inheritance of the current in-contract situation. If you have a complex 
> contract, then having to repeat it on every class seems unnecessarily 
> verbose. It's very easy to just say `in {}` if you now can accept all 
> possible parameters. The opposite is not as easy.

I would bet money that at least 50% of the time contract inheritance is 
used, people use base contracts to mean THE contract, and don't put 
contracts on derived functions, and they don't even realize it.

-Steve