src/tools/clippy/tests/ui/map_flatten_fixable.rs

   1 // run-rustfix
   2
   3 #![warn(clippy::all, clippy::pedantic)]
   4 #![allow(clippy::missing_docs_in_private_items)]
   5 #![allow(clippy::map_identity)]
   6 #![allow(clippy::redundant_closure)]
   7 #![allow(clippy::unnecessary_wraps)]
   8 #![feature(result_flattening)]
   9
  10 fn main() {
  11     // mapping to Option on Iterator
  12     fn option_id(x: i8) -> Option<i8> {
  13         Some(x)
  14     }
  15     let option_id_ref: fn(i8) -> Option<i8> = option_id;
  16     let option_id_closure = |x| Some(x);
  17     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id).flatten().collect();
  18     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_ref).flatten().collect();
  19     let _: Vec<_> = vec![5_i8; 6].into_iter().map(option_id_closure).flatten().collect();
  20     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| x.checked_add(1)).flatten().collect();
  21
  22     // mapping to Iterator on Iterator
  23     let _: Vec<_> = vec![5_i8; 6].into_iter().map(|x| 0..x).flatten().collect();
  24
  25     // mapping to Option on Option
  26     let _: Option<_> = (Some(Some(1))).map(|x| x).flatten();
  27
  28     // mapping to Result on Result
  29     let _: Result<_, &str> = (Ok(Ok(1))).map(|x| x).flatten();
  30
  31     issue8734();
  32     issue8878();
  33 }
  34
  35 fn issue8734() {
  36     let _ = [0u8, 1, 2, 3]
  37         .into_iter()
  38         .map(|n| match n {
  39             1 => [n
  40                 .saturating_add(1)
  41                 .saturating_add(1)
  42                 .saturating_add(1)
  43                 .saturating_add(1)
  44                 .saturating_add(1)
  45                 .saturating_add(1)
  46                 .saturating_add(1)
  47                 .saturating_add(1)],
  48             n => [n],
  49         })
  50         .flatten();
  51 }
  52
  53 #[allow(clippy::bind_instead_of_map)] // map + flatten will be suggested to `and_then`, but afterwards `map` is suggested again
  54 #[rustfmt::skip] // whitespace is important for this one
  55 fn issue8878() {
  56     std::collections::HashMap::<u32, u32>::new()
  57         .get(&0)
  58         .map(|_| {
  59 // we need some newlines
  60 // so that the span is big enough
  61 // for a split output of the diagnostic
  62             Some("")
  63  // whitespace beforehand is important as well
  64         })
  65         .flatten();
  66 }