[adrusi]

It would be up to the caller which knows the concrete type of the value getting passed as `any` to provide an interface object with a function pointer to the concrete instantiation of `Write[T]` for T=byte. If the immediate caller also doesn't know the concrete type, it would also get that from its caller. It's ultimately very fragile, since there are definitely cases where at no point in the caller chain does anyone statically know the concrete type (like if this value is pulled from a global variable with an interface type).

I think it would be terrible to include in the language because of the inconsistencies, but it is possible to make the two examples you listed as typical cases of interface->interface coercion work with generic methods, ugly as it may be.