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

use std::{
    cmp::PartialEq,
    fmt,
    ops::{Deref, DerefMut},
};

pub use crate::{cell::Cell, cell_ref::CellRef, cell_ref_mut::CellRefMut};

/// Mutable reference to a value.
pub struct RefMut<'a, V>
where
    V: 'a,
{
    pub(crate) inner: CellRefMut<'a, V>,
}

impl<'a, V> fmt::Debug for RefMut<'a, V>
where
    V: fmt::Debug + 'a,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let inner: &V = self;
        f.debug_struct("RefMut").field("inner", inner).finish()
    }
}

impl<'a, V> PartialEq for RefMut<'a, V>
where
    V: PartialEq + 'a,
{
    fn eq(&self, other: &Self) -> bool {
        let r_self: &V = self;
        let r_other: &V = other;
        r_self == r_other
    }
}

impl<'a, V> RefMut<'a, V> {
    pub fn new(inner: CellRefMut<'a, V>) -> Self {
        Self { inner }
    }
}

impl<'a, V> Deref for RefMut<'a, V> {
    type Target = V;

    fn deref(&self) -> &V {
        &self.inner
    }
}

impl<'a, V> DerefMut for RefMut<'a, V> {
    fn deref_mut(&mut self) -> &mut V {
        &mut self.inner
    }
}

#[cfg(test)]
mod tests {
    use std::{
        fmt::{self, Write},
        sync::atomic::AtomicUsize,
    };

    use crate::CellRefMut;

    use super::RefMut;

    #[test]
    fn debug_includes_inner_field() -> fmt::Result {
        let flag = AtomicUsize::new(0);
        let mut value = A(1);
        let ref_mut = RefMut::new(CellRefMut {
            flag: &flag,
            value: &mut value,
        });

        let mut debug_string = String::with_capacity(64);
        write!(&mut debug_string, "{:?}", ref_mut)?;
        assert_eq!("RefMut { inner: A(1) }", debug_string.as_str());

        Ok(())
    }

    #[test]
    fn partial_eq_compares_value() -> fmt::Result {
        let flag = AtomicUsize::new(0);
        let mut value = A(1);
        let mut value_clone = value.clone();
        let ref_mut = RefMut::new(CellRefMut {
            flag: &flag,
            value: &mut value,
        });

        assert_eq!(
            RefMut::new(CellRefMut {
                flag: &flag,
                value: &mut value_clone,
            }),
            ref_mut
        );
        assert_ne!(
            RefMut::new(CellRefMut {
                flag: &flag,
                value: &mut A(2),
            }),
            ref_mut
        );

        Ok(())
    }

    #[test]
    fn deref_mut_returns_value() -> fmt::Result {
        let flag = AtomicUsize::new(0);
        let mut value = A(1);
        let mut ref_mut = RefMut::new(CellRefMut {
            flag: &flag,
            value: &mut value,
        });

        assert_eq!(
            RefMut::new(CellRefMut {
                flag: &flag,
                value: &mut A(1),
            }),
            ref_mut
        );

        ref_mut.0 = 2;

        assert_eq!(
            RefMut::new(CellRefMut {
                flag: &flag,
                value: &mut A(2),
            }),
            ref_mut
        );

        Ok(())
    }

    #[derive(Debug, Clone, PartialEq)]
    struct A(usize);
}