not sure I'm completely getting the necessity of Rc; per the book, this would not work: enum List { Cons(i32, &List), Nil, } fn main() { let x = Cons(3, &Nil); } because, the Nil would get dropped before you can take a ref to it
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I think that's the thing that hadn't clicked: having this: enum List<'a> { Cons(i32, &'a List), Nil, } it's not painful necessarily b/c the &'a List must outlive the outer List -- it's that something else needs to own the inner List
Exactly. Since *something* has to own the inner node, you can't do non-trivial things to lists in a function. e.g. fn list(x: i32, y: i32) -> List<'static> { Cons(x, &Cons(y, &Nil)) } `&Nil` is actually fine since `Nil` is a constant value, but `&Cons(y` is invalid
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Playground example for completeness. Only list2 fails to compile. https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=08be5beb0e15553451f4decf0919c969 …
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