Is it possible to use `impl Trait` as a function’s return type in a trait definition?
As trentcl mentions, you cannot currently place impl Trait in the return position of a trait method. From RFC 1522: impl Trait may only be written within the return type of a freestanding or inherent-impl function, not in trait definitions or any non-return type position. They may also not appear in the return type of … Read more