I’m preparing a presentation on subtyping and variance and wanted to check that given that the normal
fn(T) -> U is covariant wrt U and contravariant wrt T, and because
extern types are bivariant, then why
extern fn(T) -> U preserves that variance wrt U, T?
shouldn’t xform be applied? is
extern a form of type composition or type aggregate? or why GLB is applied?