Digraph

Subtyping and Variance - The Rustonomiconhttps://doc.rust-lang.org/nomicon/subtyping.html

https://stackoverflow.com/questions/50671177/specify-fn-trait-bound-on-struct-definition-without-fixing-one-of-the-fn-par

rfcs/text/0738-variance.md at master · rust-lang/rfcs · GitHubhttps://github.com/rust-lang/rfcs/blob/master/text/0738-variance.md

rust - "parameter `'a` is never used" error when 'a is used in type parameter bound - Stack Overflowhttps://stackoverflow.com/questions/40484154/parameter-a-is-never-used-error-when-a-is-used-in-type-parameter-bound

rust - How can I avoid PhantomData in this struct definition? - Stack Overflowhttps://stackoverflow.com/questions/52188141/how-can-i-avoid-phantomdata-in-this-struct-definition