tests/ui/lint/noop-method-call.rs

   1 // check-pass
   2
   3 #![allow(unused)]
   4 #![warn(noop_method_call)]
   5
   6 use std::borrow::Borrow;
   7 use std::ops::Deref;
   8
   9 struct PlainType<T>(T);
  10
  11 #[derive(Clone)]
  12 struct CloneType<T>(T);
  13
  14 fn main() {
  15     let non_clone_type_ref = &PlainType(1u32);
  16     let non_clone_type_ref_clone: &PlainType<u32> = non_clone_type_ref.clone();
  17     //~^ WARNING call to `.clone()` on a reference in this situation does nothing
  18
  19     let clone_type_ref = &CloneType(1u32);
  20     let clone_type_ref_clone: CloneType<u32> = clone_type_ref.clone();
  21
  22     let clone_type_ref = &&CloneType(1u32);
  23     let clone_type_ref_clone: &CloneType<u32> = clone_type_ref.clone();
  24     //~^ WARNING using `.clone()` on a double reference, which returns `&CloneType<u32>`
  25
  26     let non_deref_type = &PlainType(1u32);
  27     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
  28     //~^ WARNING call to `.deref()` on a reference in this situation does nothing
  29
  30     let non_deref_type = &&PlainType(1u32);
  31     let non_deref_type_deref: &PlainType<u32> = non_deref_type.deref();
  32     //~^ WARNING using `.deref()` on a double reference, which returns `&PlainType<u32>`
  33
  34     let non_borrow_type = &PlainType(1u32);
  35     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
  36     //~^ WARNING call to `.borrow()` on a reference in this situation does nothing
  37
  38     // Borrowing a &&T does not warn since it has collapsed the double reference
  39     let non_borrow_type = &&PlainType(1u32);
  40     let non_borrow_type_borrow: &PlainType<u32> = non_borrow_type.borrow();
  41
  42     let xs = ["a", "b", "c"];
  43     let _v: Vec<&str> = xs.iter().map(|x| x.clone()).collect(); // could use `*x` instead
  44     //~^ WARNING using `.clone()` on a double reference, which returns `&str`
  45 }
  46
  47 fn generic<T>(non_clone_type: &PlainType<T>) {
  48     non_clone_type.clone();
  49     //~^ WARNING call to `.clone()` on a reference in this situation does nothing
  50 }
  51
  52 fn non_generic(non_clone_type: &PlainType<u32>) {
  53     non_clone_type.clone();
  54     //~^ WARNING call to `.clone()` on a reference in this situation does nothing
  55 }