The address of a sequence is where the sequence resides in memory. It just so happens that it stores the size and capacity before its elements (how else would it work?). To get the address of its first element, use `addr s[0]`. This expression also works with arrays so you don't need any special casing.
It could be documented better, sure, but then it's "immediately obvious" for anybody who is allowed to use `addr` (unsafe!). ;-)
