/
lint-unused-mut-variables.rs
145 lines (106 loc) · 3.26 KB
/
lint-unused-mut-variables.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Exercise the unused_mut attribute in some positive and negative cases
#![allow(unused_assignments)]
#![allow(unused_variables)]
#![allow(dead_code)]
#![deny(unused_mut)]
fn main() {
// negative cases
let mut a = 3; //~ ERROR: variable does not need to be mutable
let mut a = 2; //~ ERROR: variable does not need to be mutable
let mut b = 3; //~ ERROR: variable does not need to be mutable
let mut a = vec![3]; //~ ERROR: variable does not need to be mutable
let (mut a, b) = (1, 2); //~ ERROR: variable does not need to be mutable
let mut a; //~ ERROR: variable does not need to be mutable
a = 3;
let mut b; //~ ERROR: variable does not need to be mutable
if true {
b = 3;
} else {
b = 4;
}
match 30 {
mut x => {} //~ ERROR: variable does not need to be mutable
}
match (30, 2) {
(mut x, 1) | //~ ERROR: variable does not need to be mutable
(mut x, 2) |
(mut x, 3) => {
}
_ => {}
}
let x = |mut y: isize| 10; //~ ERROR: variable does not need to be mutable
fn what(mut foo: isize) {} //~ ERROR: variable does not need to be mutable
let mut a = &mut 5; //~ ERROR: variable does not need to be mutable
*a = 4;
let mut a = 5;
let mut b = (&mut a,); //~ ERROR: variable does not need to be mutable
*b.0 = 4;
let mut x = &mut 1; //~ ERROR: variable does not need to be mutable
let mut f = || {
*x += 1;
};
f();
fn mut_ref_arg(mut arg : &mut [u8]) -> &mut [u8] {
&mut arg[..] //~^ ERROR: variable does not need to be mutable
}
let mut v : &mut Vec<()> = &mut vec![]; //~ ERROR: variable does not need to be mutable
v.push(());
// positive cases
let mut a = 2;
a = 3;
let mut a = Vec::new();
a.push(3);
let mut a = Vec::new();
callback(|| {
a.push(3);
});
let mut a = Vec::new();
callback(|| {
callback(|| {
a.push(3);
});
});
let (mut a, b) = (1, 2);
a = 34;
match 30 {
mut x => {
x = 21;
}
}
match (30, 2) {
(mut x, 1) |
(mut x, 2) |
(mut x, 3) => {
x = 21
}
_ => {}
}
let x = |mut y: isize| y = 32;
fn nothing(mut foo: isize) { foo = 37; }
// leading underscore should avoid the warning, just like the
// unused variable lint.
let mut _allowed = 1;
}
fn callback<F>(f: F) where F: FnOnce() {}
// make sure the lint attribute can be turned off
#[allow(unused_mut)]
fn foo(mut a: isize) {
let mut a = 3;
let mut b = vec![2];
}
// make sure the lint attribute can be turned off on let statements
#[deny(unused_mut)]
fn bar() {
#[allow(unused_mut)]
let mut a = 3;
let mut b = vec![2]; //~ ERROR: variable does not need to be mutable
}