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

   1 // run-rustfix
   2
   3 #[warn(clippy::all, clippy::needless_borrow)]
   4 #[allow(unused_variables, clippy::unnecessary_mut_passed)]
   5 fn main() {
   6     let a = 5;
   7     let ref_a = &a;
   8     let _ = x(&a); // no warning
   9     let _ = x(&&a); // warn
  10
  11     let mut b = 5;
  12     mut_ref(&mut b); // no warning
  13     mut_ref(&mut &mut b); // warn
  14
  15     let s = &String::from("hi");
  16     let s_ident = f(&s); // should not error, because `&String` implements Copy, but `String` does not
  17     let g_val = g(&Vec::new()); // should not error, because `&Vec<T>` derefs to `&[T]`
  18     let vec = Vec::new();
  19     let vec_val = g(&vec); // should not error, because `&Vec<T>` derefs to `&[T]`
  20     h(&"foo"); // should not error, because the `&&str` is required, due to `&Trait`
  21     let garbl = match 42 {
  22         44 => &a,
  23         45 => {
  24             println!("foo");
  25             &&a
  26         },
  27         46 => &&a,
  28         47 => {
  29             println!("foo");
  30             loop {
  31                 println!("{}", a);
  32                 if a == 25 {
  33                     break &ref_a;
  34                 }
  35             }
  36         },
  37         _ => panic!(),
  38     };
  39
  40     let _ = x(&&&a);
  41     let _ = x(&mut &&a);
  42     let _ = x(&&&mut b);
  43     let _ = x(&&ref_a);
  44     {
  45         let b = &mut b;
  46         x(&b);
  47     }
  48 }
  49
  50 #[allow(clippy::needless_borrowed_reference)]
  51 fn x(y: &i32) -> i32 {
  52     *y
  53 }
  54
  55 fn mut_ref(y: &mut i32) {
  56     *y = 5;
  57 }
  58
  59 fn f<T: Copy>(y: &T) -> T {
  60     *y
  61 }
  62
  63 fn g(y: &[u8]) -> u8 {
  64     y[0]
  65 }
  66
  67 trait Trait {}
  68
  69 impl<'a> Trait for &'a str {}
  70
  71 fn h(_: &dyn Trait) {}