nothing 0.1.12

Probably a better Option
Documentation 
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

#![doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/README.md"))]

#![feature(try_trait_v2)]

/// [Probably] is a better [Option]:
/// - [Something] is like [Some]
/// - [Nothing] is like [None]
#[derive(is_macro::Is, Clone, Copy, PartialOrd, Ord, PartialEq, Eq, Debug, Hash, Default)]
pub enum Probably<T> {
    /// No value.
    #[default]
    Nothing,
    /// Some value of type `T`.
    Something(T),
}

pub use Probably::{Nothing, Something};

impl<T> std::process::Termination for Probably<T> {
    fn report(self) -> std::process::ExitCode {
        match self {
            Nothing => std::process::ExitCode::FAILURE,
            _ => std::process::ExitCode::SUCCESS,
        }
    }
}

impl<T> std::ops::FromResidual for Probably<T> {
    fn from_residual(residual: Probably<std::convert::Infallible>) -> Self {
        match residual {
            Nothing => Nothing,
            Something(_) => todo!(),
        }
    }
}

impl<T> std::ops::Try for Probably<T> {
    type Output = T;
    type Residual = Probably<std::convert::Infallible>;

    fn from_output(output: Self::Output) -> Self {
        Something(output)
    }

    fn branch(self) -> std::ops::ControlFlow<Self::Residual, Self::Output> {
        match self {
            Something(v) => std::ops::ControlFlow::Continue(v),
            Nothing => std::ops::ControlFlow::Break(Nothing),
        }
    }
}

impl<T> From<T> for Probably<T> {
    fn from(x: T) -> Self {
        Something(x)
    }
}

impl<T> From<Option<T>> for Probably<T> {
    fn from(x: Option<T>) -> Self {
        match x {
            Some(v) => Something(v),
            None => Nothing,
        }
    }
}

impl<T> Into<Option<T>> for Probably<T> {
    fn into(self) -> Option<T> {
        match self {
            Something(x) => Some(x),
            Nothing => None,
        }
    }
}

impl<T> Probably<Probably<T>> {
    /// Converts from `Probably<Probably<T>>` to `Probably<T>`.
    ///
    /// # Examples
    ///
    /// Basic usage:
    ///
    /// ```
    /// let x: Probably<Probably<u32>> = Something(Something(6));
    /// assert_eq!(Something(6), x.flatten());
    ///
    /// let x: Probably<Probably<u32>> = Something(Nothing);
    /// assert_eq!(Nothing, x.flatten());
    ///
    /// let x: Probably<Probably<u32>> = Nothing;
    /// assert_eq!(Nothing, x.flatten());
    /// ```
    ///
    ///
    /// Flattening only removes one level of nesting at a time:
    ///
    /// ```
    /// let x: Probably<Probably<Probably<u32>>> = Something(Something(Something(6)));
    /// assert_eq!(Something(Something(6)), x.flatten());
    /// assert_eq!(Something(6), x.flatten().flatten());
    /// ```
    pub fn flatten(self) -> Probably<T> {
        match self {
            Something(inner) => inner,
            Nothing => Nothing,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works() {
        let result = 2 + 2;
        assert_eq!(result, 4);
    }

    #[test]
    fn from_option_works() {
        let some = Some(42u8);
        let sth: Probably<u8> = some.into();
        assert_eq!(sth, Something(42u8));
    }

    #[test]
    fn from_unit_works() {
        let unit = ();
        let sth: Probably<()> = unit.into();
        assert_eq!(sth, Something(()));
    }

    #[test]
    fn from_some_works() {
        let unit = Some(());
        let sth: Probably<()> = unit.into();
        assert_eq!(sth, Something(()));
    }
}