src/test/compile-fail/lint-unused-mut-variables.rs

   1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Exercise the unused_mut attribute in some positive and negative cases
  12
  13 #![allow(unused_assignments)]
  14 #![allow(unused_variables)]
  15 #![allow(dead_code)]
  16 #![deny(unused_mut)]
  17
  18
  19 fn main() {
  20     // negative cases
  21     let mut a = 3; //~ ERROR: variable does not need to be mutable
  22     let mut a = 2; //~ ERROR: variable does not need to be mutable
  23     let mut b = 3; //~ ERROR: variable does not need to be mutable
  24     let mut a = vec!(3); //~ ERROR: variable does not need to be mutable
  25     let (mut a, b) = (1, 2); //~ ERROR: variable does not need to be mutable
  26
  27     match 30 {
  28         mut x => {} //~ ERROR: variable does not need to be mutable
  29     }
  30     match (30, 2) {
  31       (mut x, 1) | //~ ERROR: variable does not need to be mutable
  32       (mut x, 2) |
  33       (mut x, 3) => {
  34       }
  35       _ => {}
  36     }
  37
  38     let x = |mut y: isize| 10; //~ ERROR: variable does not need to be mutable
  39     fn what(mut foo: isize) {} //~ ERROR: variable does not need to be mutable
  40
  41     // positive cases
  42     let mut a = 2;
  43     a = 3;
  44     let mut a = Vec::new();
  45     a.push(3);
  46     let mut a = Vec::new();
  47     callback(|| {
  48         a.push(3);
  49     });
  50     let (mut a, b) = (1, 2);
  51     a = 34;
  52
  53     match 30 {
  54         mut x => {
  55             x = 21;
  56         }
  57     }
  58
  59     match (30, 2) {
  60       (mut x, 1) |
  61       (mut x, 2) |
  62       (mut x, 3) => {
  63         x = 21
  64       }
  65       _ => {}
  66     }
  67
  68     let x = |mut y: isize| y = 32;
  69     fn nothing(mut foo: isize) { foo = 37; }
  70
  71     // leading underscore should avoid the warning, just like the
  72     // unused variable lint.
  73     let mut _allowed = 1;
  74 }
  75
  76 fn callback<F>(f: F) where F: FnOnce() {}
  77
  78 // make sure the lint attribute can be turned off
  79 #[allow(unused_mut)]
  80 fn foo(mut a: isize) {
  81     let mut a = 3;
  82     let mut b = vec!(2);
  83 }