[gwervc]

> The whole point of an interface is to allow for multiple concrete implementations.

The issue is that in this case the second method may not be an implementation of the interface at all in the first place, simply a method that happens to have the same signature. That can happen easily when parameters are only built-in or BCL types.

[hansvm]

Why does that matter though? Looking at the concrete `Read` example above, what semantics might apply to an IReader vs a class which happens to accidentally conform to the interface? If a person asked for an IReader argument and found your class instead, why would they be upset?

[jen20]

The problem here is one of perspective. Interfaces in Go belong to consumers not producers.

So sure, your “I used something that matches X but isn’t really X” is possible, but practically it doesn’t happen.