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
|
use core::{
cell::Cell,
sync::atomic::{AtomicUsize, Ordering::SeqCst},
};
use once_cell::unsync::Lazy;
#[test]
fn lazy_new() {
let called = Cell::new(0);
let x = Lazy::new(|| {
called.set(called.get() + 1);
92
});
assert_eq!(called.get(), 0);
let y = *x - 30;
assert_eq!(y, 62);
assert_eq!(called.get(), 1);
let y = *x - 30;
assert_eq!(y, 62);
assert_eq!(called.get(), 1);
}
#[test]
fn lazy_deref_mut() {
let called = Cell::new(0);
let mut x = Lazy::new(|| {
called.set(called.get() + 1);
92
});
assert_eq!(called.get(), 0);
let y = *x - 30;
assert_eq!(y, 62);
assert_eq!(called.get(), 1);
*x /= 2;
assert_eq!(*x, 46);
assert_eq!(called.get(), 1);
}
#[test]
fn lazy_force_mut() {
let called = Cell::new(0);
let mut x = Lazy::new(|| {
called.set(called.get() + 1);
92
});
assert_eq!(called.get(), 0);
let v = Lazy::force_mut(&mut x);
assert_eq!(called.get(), 1);
*v /= 2;
assert_eq!(*x, 46);
assert_eq!(called.get(), 1);
}
#[test]
fn lazy_get_mut() {
let called = Cell::new(0);
let mut x: Lazy<u32, _> = Lazy::new(|| {
called.set(called.get() + 1);
92
});
assert_eq!(called.get(), 0);
assert_eq!(*x, 92);
let mut_ref: &mut u32 = Lazy::get_mut(&mut x).unwrap();
assert_eq!(called.get(), 1);
*mut_ref /= 2;
assert_eq!(*x, 46);
assert_eq!(called.get(), 1);
}
#[test]
fn lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
struct Foo(u8);
impl Default for Foo {
fn default() -> Self {
CALLED.fetch_add(1, SeqCst);
Foo(42)
}
}
let lazy: Lazy<std::sync::Mutex<Foo>> = <_>::default();
assert_eq!(CALLED.load(SeqCst), 0);
assert_eq!(lazy.lock().unwrap().0, 42);
assert_eq!(CALLED.load(SeqCst), 1);
lazy.lock().unwrap().0 = 21;
assert_eq!(lazy.lock().unwrap().0, 21);
assert_eq!(CALLED.load(SeqCst), 1);
}
#[test]
fn lazy_into_value() {
let l: Lazy<i32, _> = Lazy::new(|| panic!());
assert!(matches!(Lazy::into_value(l), Err(_)));
let l = Lazy::new(|| -> i32 { 92 });
Lazy::force(&l);
assert!(matches!(Lazy::into_value(l), Ok(92)));
}
#[test]
#[cfg(feature = "std")]
fn lazy_poisoning() {
let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
for _ in 0..2 {
let res = std::panic::catch_unwind(|| x.len());
assert!(res.is_err());
}
}
#[test]
// https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
fn arrrrrrrrrrrrrrrrrrrrrr() {
let lazy: Lazy<&String, _>;
{
let s = String::new();
lazy = Lazy::new(|| &s);
_ = *lazy;
}
}
|
