> It's not present in the syntax, but it's present in the type system.
The trickiness of the bug is that the design of contravariance means the constraint is actually not present in the type system even though it should be. See this other comment I wrote: https://news.ycombinator.com/item?id=39448909
The trickiness of the bug is that the design of contravariance means the constraint is actually not present in the type system even though it should be. See this other comment I wrote: https://news.ycombinator.com/item?id=39448909