Some examples:

- You can accidentally implement an interface.

- Lack of a proper ownership model can lead to unexpected results, which leads to bugs. Consider e.g. growing of slices:

https://play.golang.org/p/3qfd5B8_ktK

- nil is not equal to nil:

https://golang.org/doc/faq#nil_error

(Obviously, it is is easy to move the goalposts without a proper definition of 'correctness' ;).)

I think correctness is the wrong word. Maybe safety would be better? (Verboseness? Precision?)

Go is quite a stable language. Well-specified, rigorously tested, and conservatively updated.

I think all the behavior you listed is well-defined, albeit perhaps unexpected.

Lack of generics doesn't make code incorrect. Less clear maybe, or easier to make a mistake. Or clearer and a lot more code.

I guess you could argue that it makes writing correct code harder?

I think danieldk specified what he meant: Lack of generics means that you have to copy and paste. He defines "forces you to copy and paste due to lack of generics" as "incorrect for a language".

I think he's stretching the definition of "correctness" past the breaking point, but that clearly was what he meant.

Nil pointers?