In this example: fn collect<B: FromIterator<Self::Item>>(self) -> B where Self:Sized; I thought this was universal, not existential like the podcast claim

In this example: fn collect<B: FromIterator<Self::Item>>(self) -> B where Self:Sized; I thought this was universal, not existential like the podcast claims. It would be existential if you instead wrote: fn collect(self) -> impl FromIterator<Self::Item> where Self:Sized; The latter is what got added in 1.26, whereas the former was already available before that. And really, you wouldn't want to use the latter in this case because the user wants to choose the type that's being generated (this is not a case where you want the callee to choose the type). So the second signature wouldn't make a whole lot of sense even if this API had been stabilized post-1.26.