Yeah, I totally agree -- given Go's design, the behavior makes sense (and changing the behavior just to make it more familiar to users of languages that fundamentally work differently would be silly).

However, the non-intuitive punning of nil is unfortunate.

I'm not sure what the ideal design would be.

Perhaps just making an interface not comparable to nil, but instead something like `unset`.

  type Cat struct {}
  type Animal interface{} 
  
  func main() {
   var c *Cat = nil
   var a Animal = c 
   if a == nil { // compile error, can't compare interface to nil
    ;
   }
   if a == unset { // false, hopefully intuitively
   }
  }
    

(E.g. complaints about nil existing at all, or error handling, are much more relatable!)