Earlier quoted context omitted.
How is a package level interface check a “language hack”? They are straight forward and provide a user the same compile time guarantees as the Java implements keyword.
Because they are a workaround for what should be a language feature in first place, just like on ML languages to type check structural types.
What exactly isn’t a language feature? Or do you have issues with semantics?
var _ Foo = (*Bar)(nil)
I do agree it’s not as clean looking as the Java implements keyword, but it’s already a fairly terse pattern and IMO the inconvenience does not justify introducing new language syntax.