terrors 0.3.3

ergonomic and precise error handling built atop type-level set arithmetic
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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166

use terrors::OneOf;

#[derive(Debug)]
struct NotEnoughMemory;

#[derive(Debug)]
struct Timeout;

#[derive(Debug)]
struct RetriesExhausted;

#[test]
fn retry() {
    fn inner() -> Result<(), OneOf<(NotEnoughMemory, RetriesExhausted)>> {
        for _ in 0..3 {
            let Err(err) = does_stuff() else {
                return Ok(());
            };

            match err.narrow::<Timeout, _>() {
                Ok(_timeout) => continue,
                Err(allocation_oneof) => {
                    println!("didn't get Timeout, now trying to get NotEnoughMemory");
                    let allocation_oneof: OneOf<(NotEnoughMemory,)> = allocation_oneof;
                    let allocation = allocation_oneof.narrow::<NotEnoughMemory, _>().unwrap();

                    return Err(OneOf::new(allocation));
                }
            }
        }

        Err(OneOf::new(RetriesExhausted))
    }

    let _ = dbg!(inner());
}

fn does_stuff() -> Result<(), OneOf<(NotEnoughMemory, Timeout)>> {
    // TODO Try impl after superset type work
    let _allocation = match allocates() {
        Ok(a) => a,
        Err(e) => return Err(e.broaden()),
    };

    // TODO Try impl after superset type work
    let _chat = match chats() {
        Ok(c) => c,
        Err(e) => return Err(OneOf::new(e)),
    };

    Ok(())
}

fn allocates() -> Result<(), OneOf<(NotEnoughMemory,)>> {
    let result: Result<(), NotEnoughMemory> = Err(NotEnoughMemory);

    result?;

    Ok(())
}

fn chats() -> Result<(), Timeout> {
    Err(Timeout)
}

#[test]
fn smoke() {
    let o_1: OneOf<(u32, String)> = OneOf::new(5_u32);
    let _narrowed_1: u32 = o_1.narrow::<u32, _>().unwrap();

    let o_2: OneOf<(String, u32)> = OneOf::new(5_u32);
    let _narrowed_2: u32 = o_2.narrow::<u32, _>().unwrap();

    let o_3: OneOf<(String, u32)> = OneOf::new("5".to_string());
    let _narrowed_3: OneOf<(String,)> = o_3.narrow::<u32, _>().unwrap_err();

    let o_4: OneOf<(String, u32)> = OneOf::new("5".to_string());

    let _: String = o_4.narrow().unwrap();

    let o_5: OneOf<(String, u32)> = OneOf::new("5".to_string());
    o_5.narrow::<String, _>().unwrap();

    let o_6: OneOf<(String, u32)> = OneOf::new("5".to_string());
    let o_7: OneOf<(u32, String)> = o_6.broaden();
    let o_8: OneOf<(String, u32)> = o_7.subset().unwrap();
    let _: OneOf<(u32, String)> = o_8.subset().unwrap();

    let o_9: OneOf<(u8, u16, u32)> = OneOf::new(3_u32);
    let _: Result<OneOf<(u16,)>, OneOf<(u8, u32)>> = o_9.subset();
    let o_10: OneOf<(u8, u16, u32)> = OneOf::new(3_u32);
    let _: Result<u16, OneOf<(u8, u32)>> = o_10.narrow();
}

#[test]
fn debug() {
    use std::error::Error;
    use std::io;

    let o_1: OneOf<(u32, String)> = OneOf::new(5_u32);

    // Debug is implemented if all types in the type set implement Debug
    dbg!(&o_1);

    // Display is implemented if all types in the type set implement Display
    println!("{}", o_1);

    type E = io::Error;
    let e = io::Error::new(io::ErrorKind::Other, "wuaaaaahhhzzaaaaaaaa");

    let o_2: OneOf<(E,)> = OneOf::new(e);

    // std::error::Error is implemented if all types in the type set implement it
    dbg!(o_2.source());

    let o_3: OneOf<(u32, String)> = OneOf::new("hey".to_string());
    dbg!(o_3);
}

#[test]
fn multi_match() {
    use terrors::E2;

    let o_1: OneOf<(u32, String)> = OneOf::new(5_u32);

    match o_1.as_enum() {
        E2::A(u) => {
            println!("handling {u}: u32")
        }
        E2::B(s) => {
            println!("handling {s}: String")
        }
    }

    match o_1.to_enum() {
        E2::A(u) => {
            println!("handling {u}: u32")
        }
        E2::B(s) => {
            println!("handling {s}: String")
        }
    }
}

#[test]
fn multi_narrow() {
    use terrors::E2;

    struct Timeout {}
    struct Backoff {}

    let o_1: OneOf<(u8, u16, u32, u64, u128)> = OneOf::new(5_u32);

    let _narrow_res: Result<OneOf<(u8, u128)>, OneOf<(u16, u32, u64)>> = o_1.subset();

    let o_2: OneOf<(u8, u16, Backoff, Timeout, u32, u64, u128)> = OneOf::new(Timeout {});

    match o_2.subset::<(Timeout, Backoff), _>().unwrap().to_enum() {
        E2::A(Timeout {}) => {
            println!(":)");
        }
        E2::B(Backoff {}) => {
            unreachable!()
        }
    }
}