error: called `map(..).flatten()` on an `Iterator`. This is more succinctly expressed by calling `.flat_map(..)` --> $DIR/map_flatten.rs:14:21 | LL | let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try using flat_map instead: `vec![5_i8; 6].into_iter().flat_map(|x| 0..x)` | = note: `-D clippy::map-flatten` implied by `-D warnings` error: aborting due to previous error