Rust API Guidelines: Collections implement FromIterator and Extend

[oli-obk]

C-COLLECT

Clippy cannot know that a type is a collection, but it can detect types with a push or an insert method takint &mut self and one or two types respectively

[clarfonthey]

Could also check for IntoIterator or any of these three traits and make sure that they implement all of them at once.

[llogiq]

Note however that there are specialized containers that have IntoIterator but not FromIterator, e.g. Option<T>.